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Dual, 16-Bit, 1000 MSPS, TxDAC+ Digital-to-Analog Converter AD9125
FEATURES
Flexible CMOS interface allows dual-word, word, or byte load Single-carrier W-CDMA ACLR = 80 dBc at 122.88 MHz IF Analog output: adjustable 8.7 mA to 31.7 mA, RL = 25 to 50 Novel 2x/4x/8x interpolator/complex modulator allows carrier placement anywhere in the DAC bandwidth Gain and phase adjustment for sideband suppression Multichip synchronization interface High performance, low noise PLL clock multiplier Digital inverse sinc filter Low power: 900 mW at 500 MSPS, full operating conditions 72-lead, exposed paddle LFCSP
GENERAL DESCRIPTION
The AD9125 is a dual, 16-bit, high dynamic range TxDAC+(R) digital-to-analog converter (DAC) that provides a sample rate of 1000 MSPS, permitting a multicarrier generation up to the Nyquist frequency. It includes features optimized for direct conversion transmit applications, including complex digital modulation, and gain and offset compensation. The DAC outputs are optimized to interface seamlessly with analog quadrature modulators, such as the ADL537x F-MOD series from Analog Devices, Inc. A 4-wire serial port interface allows programming/readback of many internal parameters. Full-scale output current can be programmed over a range of 8.7 mA to 31.7 mA. The AD9125 comes in a 72-lead LFCSP.
APPLICATIONS
Wireless infrastructure W-CDMA, CDMA2000, TD-SCDMA, WiMAX, GSM, LTE Digital high or low IF synthesis Transmit diversity Wideband communications: LMDS/MMDS, point-to-point Cable modem termination systems
PRODUCT HIGHLIGHTS
1. Ultralow noise and intermodulation distortion (IMD) enable high quality synthesis of wideband signals from baseband to high intermediate frequencies. A proprietary DAC output switching technique enhances dynamic performance. The current outputs are easily configured for various single-ended or differential circuit topologies. The flexible CMOS digital interface allows the standard 32-wire bus to be reduced to a 16-wire bus.
2. 3. 4.
TYPICAL SIGNAL CHAIN
COMPLEX BASEBAND COMPLEX IF RF
DC
fIF
LO - fIF
2
2/4
I DAC ANTIALIASING FILTER AQM PA
DIGITAL BASEBAND PROCESSOR
2
SIN COS
2/4
Q DAC
LO
09016-001
NOTES 1. AQM = ANALOG QUADRATURE MODULATOR.
Figure 1.
Rev. 0
Information furnished by Analog Devices is believed to be accurate and reliable. However, no responsibility is assumed by Analog Devices for its use, nor for any infringements of patents or other rights of third parties that may result from its use. Specifications subject to change without notice. No license is granted by implication or otherwise under any patent or patent rights of Analog Devices. Trademarks and registered trademarks are the property of their respective owners.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A. Tel: 781.329.4700 www.analog.com Fax: 781.461.3113 (c)2010 Analog Devices, Inc. All rights reserved.
AD9125 TABLE OF CONTENTS
Features .............................................................................................. 1 Applications ....................................................................................... 1 General Description ......................................................................... 1 Product Highlights ........................................................................... 1 Typical Signal Chain......................................................................... 1 Revision History ............................................................................... 2 Functional Block Diagram .............................................................. 3 Specifications..................................................................................... 4 DC Specifications ......................................................................... 4 Digital Specifications ................................................................... 5 Latency and Power-Up Timing Specifications ......................... 5 AC Specifications.......................................................................... 6 Absolute Maximum Ratings............................................................ 7 Thermal Resistance ...................................................................... 7 ESD Caution .................................................................................. 7 Pin Configuration and Function Descriptions ............................. 8 Typical Performance Characteristics ........................................... 10 Terminology .................................................................................... 16 Theory of Operation ...................................................................... 17 Serial Port Operation ................................................................. 17 Data Format ................................................................................ 17 Serial Port Pin Descriptions ...................................................... 17 Serial Port Options ..................................................................... 18 Device Configuration Register Map ............................................ 19 Device Configuration Register Descriptions .......................... 21 CMOS Input Data Ports ................................................................ 29 Dual-Word Mode ....................................................................... 29 Word Mode ................................................................................. 29 Byte Mode .................................................................................... 29 Interface Timing ......................................................................... 30 FIFO Operation .......................................................................... 30 Digital Datapath.............................................................................. 32 Premodulation ............................................................................ 32 Interpolation Filters ................................................................... 32 NCO Modulation ....................................................................... 35 Datapath Configuration ............................................................ 35 Determining Interpolation Filter Modes ................................ 36 Datapath Configuration Example ............................................ 37 Data Rates vs. Interpolation Modes ......................................... 38 Coarse Modulation Mixing Sequences.................................... 38 Quadrature Phase Correction................................................... 39 DC Offset Correction ................................................................ 39 Inverse Sinc Filter ....................................................................... 39 DAC Input Clock Configurations ................................................ 40 DAC Input Clock Configurations ............................................ 40 Analog Outputs............................................................................... 42 Transmit DAC Operation.......................................................... 42 Auxiliary DAC Operation ......................................................... 43 Baseband Filter Implementation .............................................. 44 Driving the ADL5375-15 .......................................................... 44 Reducing LO Leakage and Unwanted Sidebands .................. 44 Device Power Dissipation.............................................................. 45 Temperature Sensor ................................................................... 46 Multichip Synchronization............................................................ 47 Synchronization with Clock Multiplication ............................... 47 Synchronization with Direct Clocking .................................... 49 Data Rate Mode Synchronization ............................................ 49 FIFO Rate Mode Synchronization ........................................... 50 Additional Synchronization Features ...................................... 51 Interrupt Request Operation ........................................................ 52 Interrupt Service Routine .......................................................... 52 Interface Timing Validation .......................................................... 53 SED Operation............................................................................ 53 SED Example .............................................................................. 53 Example Start-Up Routine ........................................................ 54 Outline Dimensions ....................................................................... 55 Ordering Guide .......................................................................... 55
REVISION HISTORY
6/10--Revision 0: Initial Version
Rev. 0 | Page 2 of 56
AD9125 FUNCTIONAL BLOCK DIAGRAM
16
1.2G DAC 1 AUX 16-BIT
IOUT1P IOUT1N
DATA RECEIVER
16 FIFO fDATA /2 PRE MOD HB1 NCO AND MOD HB2 HB3 10 I OFFSET Q OFFSET 16 16
1.2G DAC 1 AUX 16-BIT
D[31:0]
INV SINC
DACCLK
DCI FRAME
IOUT2P IOUT2N
PHASE CORRECTION
INVSINC_CLK
GAIN 1
HB1_CLK
HB2_CLK
HB3_CLK
INTP FACTOR
MODE
GAIN 2
10
10
REF AND BIAS
REFIO FSADJ
INTERNAL CLOCK TIMING AND CONTROL LOGIC DAC CLK_SEL PLL CONTROL PROGRAMMING REGISTERS SERIAL INPUT/OUTPUT PORT POWER-ON RESET MULTICHIP SYNCHRONIZATION SYNC DACCLK 0 1 PLL_LOCK CLOCK MULTIPLIER (2x TO 16x) CLK RCVR CLK RCVR
DACCLKP DACCLKN REFCLKP REFCLKN
SDIO
IRQ
RESET
SDO
SCLK
CS
Figure 2. AD9125 Functional Block Diagram
Rev. 0 | Page 3 of 56
09016-002
AD9125 SPECIFICATIONS
DC SPECIFICATIONS
TMIN to TMAX, AVDD33 = 3.3 V, DVDD18 = 1.8 V, CVDD18 = 1.8 V, IOUTFS = 20 mA, maximum sample rate, unless otherwise noted. Table 1.
Parameter RESOLUTION ACCURACY Differential Nonlinearity (DNL) Integral Nonlinearity (INL) MAIN DAC OUTPUTS Offset Error Gain Error (with Internal Reference) Full-Scale Output Current 1 Output Compliance Range Output Resistance Gain DAC Monotonicity Settling Time to Within 0.5 LSB MAIN DAC TEMPERATURE DRIFT Offset Gain Reference Voltage REFERENCE Internal Reference Voltage Output Resistance ANALOG SUPPLY VOLTAGES AVDD33 CVDD18 DIGITAL SUPPLY VOLTAGES DVDD18 IOVDD POWER CONSUMPTION 2x Mode, fDAC = 491.52 MSPS, IF = 10 MHz, PLL Off 2x Mode, fDAC = 491.52 MSPS, IF = 10 MHz, PLL On 8x Mode, fDAC = 800 MSPS, IF = 10 MHz, PLL Off AVDD33 CVDD18 DVDD18 Power-Down Mode Power Supply Rejection Ratio, AVDD33 OPERATING RANGE
1
Min
Typ 16 2.1 3.7
Max
Unit Bits LSB LSB
-0.001 -3.6 8.66 -1.0
0 2 19.6 10 Guaranteed 20 0.04 100 30 1.2 5
+0.001 +3.6 31.66 +1.0
% FSR % FSR mA V M ns ppm/C ppm/C ppm/C V k
3.13 1.71 1.71 1.71
3.3 1.8 1.8 1.8/3.3 834 913 1114 55 78 440 1.5
3.47 1.89 1.89 3.47
V V V V mW mW mW mA mA mA mW % FSR/V C
-0.3 -40
+25
1227 58 85 490 2.7 +0.3 +85
Based on a 10 k external resistor.
Rev. 0 | Page 4 of 56
AD9125
DIGITAL SPECIFICATIONS
TMIN to TMAX, AVDD33 = 3.3 V, IOVDD = 3.3 V, DVDD18 = 1.8 V, CVDD18 = 1.8 V, IOUTFS = 20 mA, maximum sample rate, unless otherwise noted. Table 2.
Parameter CMOS DATA INPUTS Input VIN Logic High Input VIN Logic Low Maximum Bus Speed SERIAL PORT OUTPUT LOGIC LEVELS Output VOUT Logic High Conditions Min 1.2 0.6 250 IOVDD = 1.8 V IOVDD = 2.5 V IOVDD = 3.3 V IOVDD = 1.8 V IOVDD = 2.5 V IOVDD = 3.3 V IOVDD = 1.8 V IOVDD = 2.5 V IOVDD = 3.3 V IOVDD = 1.8 V IOVDD = 2.5 V IOVDD = 3.3V 1.4 1.8 2.0 0.4 0.4 0.4 1.2 1.6 2.4 0.6 0.8 0.8 100 Self biased input, ac couple 1000 100 1 GHz fVCO 2.1 GHz See the Multichip Synchronization section for conditions 15.625 0 40 12.5 12.5 1.9 0.2 2.3 1.4 500 1.25 2000 600 600 500 1.25 2000 Typ Max Unit V V MHz V V V V V V V V V V V mV V MHz mV V MHz MHz MHz ns ns ns ns ns ns
Output VOUT Logic Low
SERIAL PORT INPUT LOGIC LEVELS Input VIN Logic High
Input VIN Logic Low
DACCLK INPUT (DACCLKP, DACCLKN) Differential Peak-to-Peak Voltage Common-Mode Voltage Maximum Clock Rate REFCLK INPUT (REFCLKP, REFCLKN) Differential Peak-to-Peak Voltage Common-Mode Voltage REFCLKx Frequency, PLL Mode REFCLKx Frequency, SYNC Mode SERIAL PERIPHERAL INTERFACE Maximum Clock Rate (SCLK) Minimum Pulse Width High (tPWH) Minimum Pulse Width Low (tPWOL) Setup Time, SDI to SCLK (tDS) Hold Time, SDI to SCLK (tDH) Data Valid, SDO to SCLK (tDV) Setup Time, CS to SCLK (tDCS)
LATENCY AND POWER-UP TIMING SPECIFICATIONS
Table 3.
Parameter LATENCY (DACCLK Cycles) 1x Interpolation (with or Without Modulation) 2x Interpolation (with or Without Modulation) 4x Interpolation (with or Without Modulation) 8x Interpolation (with or Without Modulation) Inverse Sinc Fine Modulation Power-Up Time
Rev. 0 | Page 5 of 56
Min
Typ 64 135 292 608 20 8 260
Max
Unit Cycles Cycles Cycles Cycles Cycles Cycles ms
AD9125
AC SPECIFICATIONS
TMIN to TMAX, AVDD33 = 3.3 V, DVDD18 = 1.8 V, CVDD18 = 1.8 V, IOUTFS = 20 mA, maximum sample rate, unless otherwise noted. Table 4.
Parameter SPURIOUS-FREE DYNAMIC RANGE (SFDR) fDAC = 100 MSPS, fOUT = 20 MHz fDAC = 200 MSPS, fOUT = 50 MHz fDAC = 400 MSPS, fOUT = 70 MHz fDAC = 800 MSPS, fOUT = 70 MHz TWO-TONE INTERMODULATION DISTORTION (IMD) fDAC = 200 MSPS, fOUT = 50 MHz fDAC = 400 MSPS, fOUT = 60 MHz fDAC = 400 MSPS, fOUT = 80 MHz fDAC = 800 MSPS, fOUT = 100 MHz NOISE SPECTRAL DENSITY (NSD) EIGHT-TONE, 500 kHz TONE SPACING fDAC = 200 MSPS, fOUT = 80 MHz fDAC = 400 MSPS, fOUT = 80 MHz fDAC = 800 MSPS, fOUT = 80 MHz W-CDMA ADJACENT CHANNEL LEAKAGE RATIO (ACLR), SINGLE CARRIER fDAC = 491.52 MSPS, fOUT = 10 MHz fDAC = 491.52 MSPS, fOUT = 122.88 MHz fDAC = 983.04 MSPS, fOUT = 122.88 MHz W-CDMA SECOND ACLR, SINGLE CARRIER fDAC = 491.52 MSPS, fOUT = 10 MHz fDAC = 491.52 MSPS, fOUT = 122.88 MHz fDAC = 983.04 MSPS, fOUT = 122.88 MHz Min Typ 78 80 69 72 84 86 84 81 -162 -163 -164 82 80 81 88 86 88 Max Unit dBc dBc dBc dBc dBc dBc dBc dBc dBm/Hz dBm/Hz dBm/Hz dBc dBc dBc dBc dBc dBc
Table 5. Interface Speeds
Mode Byte Mode Interpolation 1x 2x (HB1) 2x (HB2) 4x 8x 1x 2x (HB1) 2x (HB2) 4x 8x 1x 2x (HB1) 2x (HB2) 4x 8x fBUS 250 250 250 250 250 250 250 250 250 250 250 250 250 250 125 fDATA 62.5 62.5 62.5 62.5 62.5 125 125 125 125 125 250 250 250 250 125 fDAC 62.5 125 125 250 500 125 250 250 500 1000 250 500 500 1000 1000
Word Mode
Dual-Word Mode
Rev. 0 | Page 6 of 56
AD9125 ABSOLUTE MAXIMUM RATINGS
Table 6.
Parameter AVDD33 IOVDD DVDD18, CVDD18 AVSS EPAD CVSS DVSS FSADJ, REFIO, IOUT1P/IOUT1N, IOUT2P/IOUT2N D[31:0], FRAME, DCI DACCLKP/DACCLKN, REFCLKP/REFCLKN RESET, IRQ, CS, SCLK, SDIO, SDO Junction Temperature Storage Temperature Range With Respect To AVSS, EPAD, CVSS, DVSS AVSS, EPAD, CVSS, DVSS AVSS, EPAD, CVSS, DVSS EPAD, CVSS, DVSS AVSS, CVSS, DVSS AVSS, EPAD, DVSS AVSS, EPAD, CVSS AVSS Rating -0.3 V to +3.6 V -0.3 V to +3.6 V -0.3 V to +2.1 V -0.3 V to +0.3 V -0.3 V to +0.3 V -0.3 V to +0.3 V -0.3 V to +0.3 V -0.3 V to AVDD33 + 0.3 V
THERMAL RESISTANCE
The exposed paddle (EPAD) must be soldered to the ground plane for the 72-lead LFCSP. The EPAD performs as an electrical and thermal connection to the board. Typical JA, JB, and JC values are specified for a 4-layer board in still air. Airflow increases heat dissipation, effectively reducing JA and JB. Table 7. Thermal Resistance
Package 72-Lead LFCSP JA 20.7 JB 10.9 JC 1.1 Unit C/W Conditions EPAD soldered
ESD CAUTION
EPAD, DVSS DVSS EPAD, DVSS
-0.3 V to DVDD18 + 0.3 V -0.3 V to CVDD18 + 0.3 V -0.3 V to IOVDD + 0.3 V 125C -65C to +150C
Stresses above those listed under Absolute Maximum Ratings may cause permanent damage to the device. This is a stress rating only; functional operation of the device at these or any other conditions above those indicated in the operational section of this specification is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability.
Rev. 0 | Page 7 of 56
AD9125 PIN CONFIGURATION AND FUNCTION DESCRIPTIONS
CVDD18 CVDD18 REFCLKP REFCLKN AVDD33 IOUT1P IOUT1N AVDD33 AVSS FSADJ REFIO AVSS AVDD33 IOUT2N IOUT2P AVDD33 AVSS NC
CVDD18 DACCLKP DACCLKN CVSS FRAME NC IRQ D31 D30 NC IOVDD DVDD18 D29 D28 D27 D26 D25 D24 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18
72 71 70 69 68 67 66 65 64 63 62 61 60 59 58 57 56 55
PIN 1 INDICATOR
AD9125
TOP VIEW (Not to Scale)
54 53 52 51 50 49 48 47 46 45 44 43 42 41 40 39 38 37
RESET CS SCLK SDIO SDO DVDD18 D0 D1 D2 D3 DVSS DVDD18 D4 D5 D6 D7 D8 D9
D23 D22 D21 D20 D19 D18 D17 D16 DCI NC DVDD18 DVSS D15 D14 D13 D12 D11 D10
19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36
NOTES 1. NC = NO CONNECT. 2. EXPOSED PAD MUST BE CONNECTED TO AVSS.
Figure 3. Pin Configuration
Table 8. Pin Function Descriptions
Pin No. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 Mnemonic CVDD18 DACCLKP DACCLKN CVSS FRAME NC IRQ (INT) D31 D30 NC IOVDD DVDD18 D29 D28 D27 D26 D25 D24 D23 D22 D21 D20 D19 D18 D17 D16 DCI Description 1.8 V Clock Supply. Supplies clock receivers, clock distribution, and PLL circuitry. DAC Clock Input, Positive. DAC Clock Input, Negative. Clock Supply Common. Frame Input. No Connect Interrupt Request. Open Drain, Active Low Output. Connect external pull-up to IOVDD. Data Bit 31. Data Bit 30. No Connect. Supply for Serial Port Pin, RESET Pin, and IRQ Pin. 1.8 V to 3.3 V can be applied to this pin. 1.8 V Digital Supply. Supplies power to digital core and digital data ports. Data Bit 29. Data Bit 28. Data Bit 27. Data Bit 26. Data Bit 25. Data Bit 24. Data Bit 23. Data Bit 22. Data Bit 21. Data Bit 20. Data Bit 19. Data Bit 18. Data Bit 17. Data Bit 16. Data Clock Input.
Rev. 0 | Page 8 of 56
09016-003
AD9125
Pin No. 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 Mnemonic NC DVDD18 DVSS D15 D14 D13 D12 D11 D10 D9 D8 D7 D6 D5 D4 DVDD18 DVSS D3 D2 D1 D0 DVDD18 SDO SDIO SCLK CS RESET NC AVSS AVDD33 IOUT2P IOUT2N AVDD33 AVSS REFIO FSADJ AVSS AVDD33 IOUT1N IOUT1P AVDD33 REFCLKN REFCLKP CVDD18 CVDD18 EPAD Description No Connect. 1.8 V Digital Supply. Digital Common. Data Bit 15. Data Bit 14. Data Bit 13. Data Bit 12. Data Bit 11. Data Bit 10. Data Bit 9. Data Bit 8. Data Bit 7. Data Bit 6. Data Bit 5. Data Bit 4. 1.8 V Digital Supply. Digital Supply Common. Data Bit 3. Data Bit 2. Data Bit 1. Data Bit 0. 1.8 V Digital Supply. Serial Port Data Output (CMOS levels with respect to IOVDD). Serial Port Data Input/Output (CMOS levels with respect to IOVDD). Serial Port Clock Input (CMOS levels with respect to IOVDD). Serial Port Chip Select. Active Low (CMOS levels with respect to IOVDD). Reset. Active Low (CMOS levels with respect to IOVDD). No Connect. Analog Supply Common. 3.3 V Analog Supply. Q DAC Positive Current Output. Q DAC Negative Current Output. 3.3 V Analog Supply. Analog Supply Common. Voltage Reference. Nominally 1.2 V output. Should be decoupled to analog common. Full-Scale Current Output Adjust. Place a 10 k resistor on the analog common. Analog Common. 3.3 V Analog Supply. I DAC Negative Current Output. I DAC Positive Current Output. 3.3 V Analog Supply. PLL Reference Clock Input, Negative. This pin has a secondary function as the SYNC input. PLL Reference Clock Input, Positive. This pin has a secondary function as the SYNC input. 1.8 V Clock Supply. Supplies clock receivers, clock distribution, and PLL circuitry. 1.8 V Clock Supply. Supplies clock receivers, clock distribution, and PLL circuitry. Exposed pad must be connected to AVSS. This provides an electrical, thermal, and mechanical connection to the PCB.
Rev. 0 | Page 9 of 56
AD9125 TYPICAL PERFORMANCE CHARACTERISTICS
0 -10 -20 -50 -55 -60 0dBFS -6dBFS -12dBFS -18dBFS
fDATA = 125MSPS, SECOND HARMONIC fDATA = 125MSPS, THIRD HARMONIC fDATA = 250MSPS, SECOND HARMONIC fDATA = 250MSPS, THIRD HARMONIC
HARMONICS (dBc)
09016-101
HARMONICS (dBc)
-30 -40 -50 -60 -70 -80 -90 -100 0 50 100 150 200 250 300
-65 -70 -75 -80 -85 -90 0 50 100 150 200 250 300
fOUT (MHz)
fOUT (MHz)
Figure 4. Harmonics vs. fOUT over fDATA, 2x Interpolation, Digital Scale = 0 dBFS, fSC = 20 mA
Figure 7. Second Harmonic vs. fOUT over Digital Scale, 2x Interpolation, fDATA = 250 MSPS, fSC = 20 mA
0 -10 -20
fDATA = 125MSPS, SECOND HARMONIC fDATA = 125MSPS, THIRD HARMONIC fDATA = 250MSPS, SECOND HARMONIC fDATA = 250MSPS, THIRD HARMONIC
HARMONICS (dBc)
-50 -55 -60 -65 -70 -75 -80 -85 -90 -95 -100
09016-102 09016-105 09016-106
0dBFS -6dBFS -12dBFS -18dBFS
HARMONICS (dBc)
-30 -40 -50 -60 -70 -80 -90 -100 0 100 200 300 400 500 600
0
50
100
150
200
250
300
fOUT (MHz)
fOUT (MHz)
Figure 5. Harmonics vs. fOUT over fDATA, 4x Interpolation, Digital Scale = 0 dBFS, fSC = 20 mA
Figure 8. Third Harmonic vs. fOUT over Digital Scale, 2x Interpolation, fDATA = 250 MSPS, fSC = 20 mA
0 -10 -20
fDATA = 125MSPS, SECOND HARMONIC fDATA = 125MSPS, THIRD HARMONIC
-50 -55 -60
HARMONICS (dBc)
HARMONICS (dBc)
-30 -40 -50 -60 -70 -80 -90 -100
09016-103
-65 -70 -75 -80 -85 -90 -95 10mA, 20mA, 30mA, 10mA, 20mA, 30mA, 0 50 100 150 SECOND HARMONIC SECOND HARMONIC SECOND HARMONIC THIRD HARMONIC THIRD HARMONIC THIRD HARMONIC 200 250 300
0
100
200
300
400
500
600
fOUT (MHz)
fOUT (MHz)
Figure 6. Harmonics vs. fOUT over fDATA, 8x Interpolation, Digital Scale = 0 dBFS, fSC = 20 mA
Figure 9. Harmonics vs. fOUT over fSC, 2x Interpolation, fDATA = 250 MSPS, Digital Scale = 0 dBFS
Rev. 0 | Page 10 of 56
09016-104
AD9125
-50 -55
fDATA = 125MSPS fDATA = 250MSPS
HIGHEST DIGITAL SPUR (dBc)
-60 -65 -70 -75 -80 -85 -90 -95 0 50 100 150 200 250 300
START 1.0MHz #RES BW 10kHz
2x INTERPOLATION, SINGLE-TONE SPECTRUM, fDATA = 250MSPS, fOUT = 101MHz
fOUT (MHz)
09016-107
VBW 10kHz
STOP 500.0MHz SWEEP 6.017s (601 PTS)
Figure 10. Highest Digital Spur vs. fOUT over fDATA, 2x Interpolation, Digital Scale = 0 dBFS, fSC = 20 mA
Figure 13. 2x Interpolation, Single-Tone Spectrum
-50 -55
fDATA = 125MSPS fDATA = 250MSPS
HIGHEST DIGITAL SPUR (dBc)
4x INTERPOLATION, SINGLE-TONE SPECTRUM, fDATA = 125MSPS, fOUT = 101MHz
-60 -65 -70 -75 -80 -85 -90 0 100 200 300 400 500 600
09016-111 09016-112
fOUT (MHz)
09016-108
START 1.0MHz #RES BW 10kHz
VBW 10kHz
STOP 500.0MHz SWEEP 6.017s (601 PTS)
Figure 11. Highest Digital Spur vs. fOUT over fDATA, 4x Interpolation, Digital Scale = 0 dBFS, fSC = 20 mA
Figure 14. 4x Interpolation, Single-Tone Spectrum
-50 -55
fDATA = 125MSPS
HIGHEST DIGITAL SPUR (dBc)
-60 -65 -70 -75 -80 -85 -90 -95 0 50 100 150 200 250 300 350 400
START 1.0MHz #RES BW 10kHz
8x INTERPOLATION, SINGLE-TONE SPECTRUM, fDATA = 125MSPS, fOUT = 131MHz
fOUT (MHz)
09016-109
VBW 10kHz
STOP 1.0GHz SWEEP 12.05s (601 PTS)
Figure 12. Highest Digital Spur vs. fOUT over fDATA, 8x Interpolation, Digital Scale = 0 dBFS, fSC = 20 mA
Figure 15. 8x Interpolation, Single-Tone Spectrum
Rev. 0 | Page 11 of 56
09016-110
AD9125
-50 -55 -60 -65
IMD (dBc)
fDATA = 125MSPS fDATA = 250MSPS
-50 -55 -60 -65
IMD (dBc)
0dBFS -6dBFS -12dBFS -18dBFS
-70 -75 -80 -85 -90
09016-113
-70 -75 -80 -85 -90
0
50
100
150
200
250
300
0
50
100
150
200
250
300
fOUT (MHz)
fOUT (MHz)
Figure 16. IMD vs. fOUT over fDATA, 2x Interpolation, Digital Scale = 0 dBFS, fSC = 20 mA
Figure 19. IMD vs. fOUT over Digital Scale, 2x Interpolation, fDATA = 250 MSPS, fSC = 20 mA
-50 -55 -60 -65
IMD (dBc)
fDATA = 125MSPS fDATA = 250MSPS
-50 -55 -60 -65
IMD (dBc)
20mA 30mA 10mA
-70 -75 -80 -85 -90
09016-114
-70 -75 -80 -85 -90
0
100
200
300
400
500
600
0
50
100
150
200
250
300
fOUT (MHz)
fOUT (MHz)
Figure 17. IMD vs. fOUT over fDATA, 4x Interpolation, Digital Scale = 0 dBFS, fSC = 20 mA
Figure 20. IMD vs. fOUT over fSC, 2x Interpolation, fDATA = 250 MSPS, Digital Scale = 0 dBFS
-50 -55 -60
fDATA = 125MSPS
-40 -45 -50 -55 PLL ON
-65
IMD (dBc)
-70 -75 -80
IMD (dBc)
-60 -65 PLL OFF -70 -75 -80
-85 -90
09016-115
-85 -90 0 100 200 300 400 500 600 0 50 100 150 200 250 300
09016-118
fOUT (MHz)
fOUT (MHz)
Figure 18. IMD vs. fOUT over fDATA, 8x Interpolation, Digital Scale = 0 dBFS, fSC = 20 mA
Figure 21. IMD vs. fOUT, PLL On vs. PLL Off
Rev. 0 | Page 12 of 56
09016-117
09016-116
AD9125
-154 -156 -158 -162 -160 2x, fDATA = 250MSPS 4x, fDATA = 125MSPS 8x, fDATA = 125MSPS
-161
NSD (dBm/Hz)
-160 -162 -164 -166 -168
09016-119
NSD (dBm/Hz)
2x, fDATA = 250MSPS 4x, fDATA = 125MSPS 8x, fDATA = 125MSPS 0 100 200 300 400 500 600
-163
-164
-165
-166 0 50 100 150 200 250 300 350 400 450 500
fOUT (MHz)
fOUT (MHz)
Figure 22. One-Tone NSD vs. fOUT over Interpolation Rate and fDATA, Digital Scale = 0 dBFS, fSC = 20 mA, PLL Off
Figure 25. Eight-Tone NSD vs. fOUT over Interpolation Rate and fDATA, Digital Scale = 0 dBFS, fSC = 20 mA, PLL Off
-154 -156 -158
0dBFS -6dBFS -12dBFS -18dBFS
-161.5 -162.0 -162.5 -163.0
0dBFS -6dBFS -12dBFS -18dBFS
NSD (dBm/Hz)
NSD (dBm/Hz)
-160 -162 -164 -166
-163.5 -164.0 -164.5 -165.0 -165.5 -166.0
-168
09016-120
-166.5 0 50 100 150 200 250 0 50 100 150 200 250
fOUT (MHz)
fOUT (MHz)
Figure 23. One-Tone NSD vs. fOUT over Digital Scale, fDATA = 200 MSPS, 4x Interpolation, fSC = 20 mA, PLL Off
Figure 26. Eight-Tone NSD vs. fOUT over Digital Scale, fDATA = 200 MSPS, 4x Interpolation, fSC = 20 mA, PLL Off
-158 8x, fDATA = 125MSPS -159 -160
-160 8x, fDATA = 125MSPS -161 -162
-161
NSD (dBm/Hz)
NSD (dBm/Hz)
-162 -163 -164
-163 -164 -165
-165 -166 -167
09016-121
-166 -167 0 100 200 300 400 500 600 0 100 200 300 400 500 600
fOUT (MHz)
fOUT (MHz)
Figure 24. One-Tone NSD vs. fOUT over Interpolation Rate and fDATA, Digital Scale = 0 dBFS, fSC = 20 mA, PLL On
Figure 27. Eight-Tone NSD vs. fOUT over Interpolation Rate and fDATA, Digital Scale = 0 dBFS, fSC = 20 mA, PLL On
Rev. 0 | Page 13 of 56
09016-124
09016-123
09016-122
AD9125
-77 -78 -79 0dBFS -3dBFS -6dBFS -50 -55 -60 -65 -70 -75 -80 -85 -90
09016-125
2x, 4x, 2x, 4x,
PLL OFF PLL OFF PLL ON PLL ON
ACLR (dBc)
-80 -81 -82 -83 -84 0 50 100 150 200 250
ACLR (dBc)
0
100
200
300
400
500
fOUT (MHz)
fOUT (MHz)
Figure 28. One-Carrier W-CDMA ACLR vs. fOUT over Digital Cutback, Adjacent Channel, PLL Off
Figure 31. One-Carrier W-CDMA ACLR vs. fOUT over Interpolation Rate, Adjacent Channel, PLL On vs. PLL Off
-78 0dBFS -3dBFS -6dBFS
-70 -72 -74 -76 2x, 4x, 2x, 4x, PLL OFF PLL OFF PLL ON PLL ON
-80
-82
ACLR (dBc)
ACLR (dBc)
-78 -80 -82 -84 -86 -88
-84
-86
-88
-90
09016-126
-90 0 50 100 150 200 250 0 100 200 300 400 500
fOUT (MHz)
fOUT (MHz)
Figure 29. One-Carrier W-CDMA ACLR vs. fOUT over fDAC, Alternate Channel, PLL Off
Figure 32. One-Carrier W-CDMA ACLR vs. fOUT over Interpolation Rate, Alternate Channel, PLL On vs. PLL Off
-70 0dBFS -3dBFS -6dBFS -75
-70 2x, 4x, 2x, 4x, PLL OFF PLL OFF PLL ON PLL ON
-75
ACLR (dBc)
-80
ACLR (dBc)
-80
-85
-85
-90
-90
-95
09016-127
-95 0 50 100 150 200 250 0 100 200 300 400 500
fOUT (MHz)
fOUT (MHz)
Figure 30. One-Carrier W-CDMA ACLR vs. fOUT over fDAC, Second Alternate Channel, PLL Off
Figure 33. One-Carrier W-CDMA ACLR vs. fOUT over Interpolation Rate, Second Alternate Channel, PLL On vs. PLL Off
Rev. 0 | Page 14 of 56
09016-130
09016-129
09016-128
AD9125
START 133.06MHz #RES BW 30kHz
RMS RESULTS CARRIER POWER -10.00dBm/ 3.840MHz FREQ OFFSET 5.00MHz 10.00MHz 15.00MHz
VBW 30kHz STOP 166.94MHz SWEEP 143.6ms (601 PTS)
REF BW 3.840MHz 3.840MHz 2.888MHz LOWER dBc dBm -75.96 -85.96 -85.33 -95.33 -95.81 -95.81 UPPER dBc dBm -77.13 -87.13 -85.24 -95.25 -85.43 -95.43
START 125.88MHz #RES BW 30kHz
VBW 30kHz STOP 174.42MHz SWEEP 206.9ms (601 PTS)
09016-131
TOTAL CARRIER POWER: -11.19dBm/15.3600MHz RRC FILTER: OFF FILTER ALPHA 0.22 REF CARRIER POWER: -16.89dBm/3.84000MHz OFFSET FREQ 5.000MHz 10.00MHz 15.00MHz INTEG BW 3.840MHz 3.840MHz 3.840MHz LOWER dBc dBm -65.88 -82.76 -68.17 -85.05 -70.42 -87.31 UPPER dBc dBm -67.52 -84.40 -69.91 -86.79 -71.40 -88.28
Figure 34. Four-Carrier W-CDMA ACLR Performance, IF 150 MHz
Figure 35. One-Carrier W-CDMA ACLR Performance, IF 150 MHz
Rev. 0 | Page 15 of 56
09016-132
1 2 3 4
-16.92dBm -16.89dBm -17.43dBm -17.64dBm
AD9125 TERMINOLOGY
Integral Nonlinearity (INL) INL is defined as the maximum deviation of the actual analog output from the ideal output, determined by a straight line drawn from zero scale to full scale. Differential Nonlinearity (DNL) DNL is the measure of the variation in analog value, normalized to full scale, associated with a 1 LSB change in digital input code. Offset Error The deviation of the output current from the ideal of zero is called offset error. For IOUT1P, 0 mA output is expected when the inputs are all 0s. For IOUT1N, 0 mA output is expected when all inputs are set to 1. Gain Error The difference between the actual and ideal output span. The actual span is determined by the difference between the outputs when all inputs are set to 1 vs. when all inputs are set to 0. Output Compliance Range The range of allowable voltage at the output of a current output DAC. Operation beyond the maximum compliance limits can cause either output stage saturation or breakdown, resulting in nonlinear performance. Temperature Drift Temperature drift is specified as the maximum change from the ambient (25C) value to the value at either TMIN or TMAX. For offset and gain drift, the drift is reported in ppm of fullscale range (FSR) per degree Celsius. For reference drift, the drift is reported in ppm per degree Celsius. Power Supply Rejection (PSR) The maximum change in the full-scale output as the supplies are varied from minimum to maximum specified voltages. Settling Time The time required for the output to reach and remain within a specified error band around its final value, measured from the start of the output transition. Spurious-Free Dynamic Range (SFDR) The difference in decibels between the peak amplitude of the output signal and the peak spurious signal within the dc to the Nyquist frequency of the DAC. Typically, energy in this band is rejected by the interpolation filters. This specification, therefore, defines how well the interpolation filters work and the effect of other parasitic coupling paths to the DAC output. Signal-to-Noise Ratio (SNR) SNR is the ratio of the rms value of the measured output signal to the rms sum of all other spectral components below the Nyquist frequency, excluding the first six harmonics and dc. The value for SNR is expressed in decibels. Interpolation Filter If the digital inputs to the DAC are sampled at a multiple rate of fDATA (interpolation rate), a digital filter can be constructed that has a sharp transition band near fDATA/2. Images that typically appear around fDAC (output data rate) can be greatly suppressed. Adjacent Channel Leakage Ratio (ACLR) The ratio in decibels relative to the carrier (dBc) between the measured power within a channel and that of its adjacent channel. Complex Image Rejection In a traditional two-part upconversion, two images are created around the second IF frequency. These images have the effect of wasting transmitter power and system bandwidth. By placing the real part of a second complex modulator in series with the first complex modulator, either the upper or lower frequency image near the second IF can be rejected.
16 2 DATA LATCH INPUT DATA FORMAT 32 FIFO SIN NCO COS 16 2 2 2 2 2
16
I DAC
16
Q DAC
DCI WRITE POINTER READ POINTER
CLOCK GENERATOR AND DISTRIBUTOR
DACCLK
fINTERFACE
fDATA /fHB1
fNCO /fHB2
fHB3
fDAC
Figure 36. Defining Data Rates
Rev. 0 | Page 16 of 56
09016-136
AD9125 THEORY OF OPERATION
The AD9125 combines many features that make it a very attractive DAC for wired and wireless communications systems. The dual digital signal path and dual DAC structure allow an easy interface to common quadrature modulators when designing single sideband transmitters. The speed and performance of the AD9125 allows wider bandwidths and more carriers to be synthesized than in previously available DACs. In addition, these devices include an innovative low power, 32-bit, complex NCO that greatly increases the ease of frequency placement. The AD9125 offers features that allow simplified synchronization with incoming data and between multiple devices. Auxiliary DACs are also provided on chip for output dc offset compensation (for local oscillator [LO] compensation in single sideband [SSB] transmitters) and for gain matching (for image rejection optimization in SSB transmitters). The remaining SCLK edges are for Phase 2 of the communication cycle. Phase 2 is the actual data transfer between the device and the system controller. Phase 2 of the communication cycle is a transfer of one or more data bytes. Registers change immediately upon writing to the last bit of each transfer byte, except for the frequency tuning word and NCO phase offsets, which only change when the frequency update bit (Register 0x36, Bit 0) is set.
DATA FORMAT
The instruction byte contains the information shown in Table 9. Table 9. Serial Port Instruction Byte
I7 (MSB) R/W I6 A6 I5 A5 I4 A4 I3 A3 I2 A2 I1 A1 I0 (LSB) A0
SERIAL PORT OPERATION
The serial port is a flexible, synchronous serial communication port, allowing easy interface to many industry-standard microcontrollers and microprocessors. The serial I/O is compatible with most synchronous transfer formats, including both the Motorola SPI(R) and Intel(R) SSR protocols. The interface allows read/write access to all registers that configure the AD9125. Single- or multiple-byte transfers are supported, as well as MSBfirst or LSB-first transfer formats. The serial interface ports can be configured as a single-pin I/O (SDIO) or two unidirectional pins for input/output (SDIO/SDO).
SDO 50 SDIO 51 SCLK 52 CS 53 SPI PORT
09016-010
R/W, Bit 7 of the instruction byte, determines whether a read or write data transfer occurs after the instruction byte write. Logic 1 indicates a read operation, and Logic 0 indicates a write operation. A6 to A0, Bit 6 to Bit 0 of the instruction byte, determine the register that is accessed during the data transfer portion of the communication cycle. For multibyte transfers, A6 is the starting byte address. The remaining register addresses are generated by the device based on the LSB_FIRST bit (Register 0x00, Bit 6).
SERIAL PORT PIN DESCRIPTIONS
Serial Clock (SCLK) The serial clock pin synchronizes data to and from the device and runs the internal state machines. The maximum frequency of SCLK is 40 MHz. All data input is registered on the rising edge of SCLK. All data is driven out on the falling edge of SCLK. Chip Select (CS) An active low input starts and gates a communication cycle. It allows more than one device to be used on the same serial communication lines. The SDO and SDIO pins go to a high impedance state when this input is high. During the communication cycle, the CS pin should stay low. Serial Data I/O (SDIO) Data is always written into the device on this pin. However, this pin can be used as a bidirectional data line. The configuration of this pin is controlled by Register 0x00, Bit 7. The default is Logic 0, configuring the SDIO pin as unidirectional. Serial Data Out (SDO) Data is read from this pin for protocols that use separate lines for transmitting and receiving data. In the case where the device operates in a single bidirectional I/O mode, this pin does not output data and is set to a high impedance state.
Figure 37. Serial Port Interface Pins
There are two phases of a communication cycle with the AD9125. Phase 1 is the instruction cycle (the writing of an instruction byte into the device), which is coincident with the first eight SCLK rising edges. The instruction byte provides the serial port controller with information regarding the data transfer cycle, which is Phase 2 of the communication cycle. The Phase 1 instruction byte defines whether the upcoming data transfer is a read or write and the starting register address for the first byte of the data transfer. The first eight SCLK rising edges of each communication cycle are used to write the instruction byte into the device. A logic high on the CS pin followed by a logic low resets the serial port timing to the initial state of the instruction cycle. From this state, the next eight rising SCLK edges represent the instruction bits of the current I/O operation.
Rev. 0 | Page 17 of 56
AD9125
SERIAL PORT OPTIONS
The serial port can support both MSB-first and LSB-first data formats. This functionality is controlled by the LSB_FIRST bit (Register 0x00, Bit 6). The default is MSB-first (LSB_FIRST = 0). When LSB_FIRST = 0 (MSB-first), the instruction and data bit must be written from MSB to LSB. Multibyte data transfers in MSB-first format start with an instruction byte that includes the register address of the most significant data byte. Subsequent data bytes should follow from the high address to the low address. In MSB-first mode, the serial port internal byte address generator decrements for each data byte of the multibyte communication cycle. When LSB_FIRST = 1 (LSB-first), the instruction and data bit must be written from LSB to MSB. Multibyte data transfers in LSB-first format start with an instruction byte that includes the register address of the least significant data byte followed by multiple data bytes. The serial port internal byte address generator increments for each byte of the multibyte communication cycle. The serial port controller data address decrements from the data address written toward 0x00 for multibyte I/O operations if the MSB-first mode is active. The serial port controller address increments from the data address written toward 0x7F for multibyte I/O operations if the LSB-first mode is active.
CS SCLK INSTRUCTION CYCLE DATA TRANSFER CYCLE
SDIO
R/W A6
A5
A4 A3
A2 A1
A0
D7 D6N D5N
D30 D20 D10 D00
09016-011
SDO
D7 D6N D5N
D30 D20 D10 D00
Figure 38. Serial Register Interface Timing, MSB First
INSTRUCTION CYCLE CS SCLK
DATA TRANSFER CYCLE
SDIO
A0
A1
A2
A3 A4
N0 N1 R/W D00 D10 D20
D4N D5N D6N D7N
09016-012
SDO
D00 D10 D20
D4N D5N D6N D7 N
Figure 39. Serial Register Interface Timing, LSB First
tDS
CS
tSCLK
tPWH
SCLK
tPWL
tDS
SDIO
INSTRUCTION BIT 7
INSTRUCTION BIT 6
Figure 40. Timing Diagram for Serial Port Register Write (tDS to tDCS)
CS
SCLK
09016-014
tDV
SDIO, SDO DATA BIT n DATA BIT n - 1
Figure 41. Timing Diagram for Serial Port Register Read
Rev. 0 | Page 18 of 56
09016-013
tDH
AD9125 DEVICE CONFIGURATION REGISTER MAP
Table 10. Device Configuration Register Map
Register Name Comm Power Control Addr (Hex) 0x00 0x01 Bit 7 SDIO Powerdown DAC I Binary data format Enable PLL lock lost 0 Bit 6 LSB_FIRST Powerdown DAC Q Q data first Enable PLL lock 0 Bit 5 Reset Powerdown data receiver MSB swap Bit 4 Powerdown aux ADC Bit 3 Bit 2 Bit 1 Bit 0 PLL lock status Data bus width[1:0] Default 0x00 0x10
Data Format
0x03
0x00
Interrupt Enable 1
0x04
Interrupt Enable 2
0x05
Enable sync signal lost 0
Event Flag 1
0x06
PLL lock lost
PLL locked
Sync signal lost
Enable sync signal lock Enable AED compare pass Sync signal locked AED compare pass REFCLK crosscorrection
Enable sync phase lock Enable AED compare fail Sync phase locked AED compare fail 1
Enable soft FIFO sync Enable SED compare fail Soft FIFO sync SED compare fail 1
Enable FIFO Warning 1 0
Enable FIFO Warning 2 0
0x00
0x00
FIFO Warning 1
FIFO Warning 2
N/A
Event Flag 2
0x07
N/A
Clock Receiver Control PLL Control 1
0x08
0x0A
DACCLK duty correction PLL enable
PLL Control 2 PLL Control 3
0x0C 0x0D
REFCLK DACCLK duty crosscorrection correction PLL manual enable PLL loop bandwidth[2:0] N2[1:0]
1
1
0x3F
Manual VCO band[5:0]
0x40
PLL charge pump current[4:0] PLL cross control enable N0[1:0] N1[1:0]
0xD1 0xD9
PLL Status 1 PLL Status 2 Sync Control 1 Sync Control 2 Sync Status 1 Sync Status 2 FIFO Control FIFO Status 1
0x0E 0x0F 0x10 0x11 0x12 0x13 0x17 0x18
PLL lock Sync enable Sync lost Data/FIFO rate toggle Sync locked
VCO control voltage[3:0] VCO band readback[5:0] Rising Sync Averaging[2:0] edge sync Sync phase request[5:0]
0x00 0x00 0x48 0x00 N/A
Sync phase readback[7:0] (6.2 format) FIFO phase offset[2:0] FIFO Warning 1 FIFO Warning 2 FIFO level[7:0] Bypass premod Bypass sinc-1 Bypass NCO NCO gain Bypass Select sideband phase compensation and dc offset HB1[1:0] Send I data to Q data FIFO soft align ack FIFO soft align request FIFO reset aligned
N/A 0x04 N/A
FIFO Status 2 Datapath Control
0x19 0x1B
N/A 0xE4
HB1 Control HB2 Control HB3 Control Chip ID
0x1C 0x1D 0x1E 0x1F HB2[5:0] HB3[5:0] Chip ID[7:0]
Rev. 0 | Page 19 of 56
Bypass HB1 Bypass HB2 Bypass HB3
0x00 0x00 0x00 0x08
AD9125
Register Name FTW 1 (LSB) FTW 2 FTW 3 FTW 4 (MSB) NCO Phase Offset LSB NCO Phase Offset MSB NCO FTW Update Addr (Hex) 0x30 0x31 0x32 0x33 0x34 0x35 0x36 Frame FTW ack Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 FTW[7:0] FTW[15:8] FTW[23:16] FTW[31:24] NCO phase offset[7:0] NCO phase offset[15:8] Frame FTW request I phase adjust[7:0] I phase adjust[9:8] Q phase adjust[7:0] Q phase adjust[9:8] I DAC offset[7:0] I DAC offset[15:8] Q DAC offset[7:0] Q DAC offset[15:8] I DAC FS adjust[7:0] I DAC sleep I aux DAC[7:0] I Aux DAC sign I Aux DAC current direction I aux DAC sleep Q DAC FS adjust[7:0] Q DAC sleep Q aux DAC[7:0] Q Aux DAC sign Q Aux DAC current direction Q aux DAC sleep FS current[2:0] Die temperature[7:0] Die temperature[15:8] SED compare enable Sample error detected Autoclear enable Compare Value I0[7:0] Compare Value I0[15:8] Compare Value Q0[7:0] Compare Value Q0[15:8] Compare Value I1[7:0] Compare Value I1[15:8] Compare Value Q1[7:0] Compare fail Compare pass Q aux DAC[9:8] Q DAC FS adjust[9:8] I aux DAC[9:8] I DAC FS adjust[9:8] Update FTW ack Update FTW request Bit 2 Bit 1 Bit 0 Default 0x00 0x00 0x00 0x00 0x00 0x00 0x00
I Phase Adj LSB I Phase Adj MSB Q Phase Adj LSB Q Phase Adj MSB I DAC Offset LSB I DAC Offset MSB Q DAC Offset LSB Q DAC Offset MSB I DAC FS Adjust I DAC Control Aux DAC I Data I Aux DAC Control Q DAC FS Adjust Q DAC Control Aux DAC Q Data Q Aux DAC Control Die Temperature Range Control Die Temperature LSB Die Temperature MSB SED Control
0x38 0x39 0x3A 0x3B 0x3C 0x3D 0x3E 0x3F 0x40 0x41 0x42 0x43
0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0xF9 0x01 0x00 0x00
0x44 0x45 0x46 0x47
0xF9 0x01 0x00 0x00
0x48 0x49 0x4A 0x67
Reference current[2:0]
Capacitor value
0x02 N/A N/A 0x00
Compare I0 LSBs Compare I0 MSBs Compare Q0 LSBs Compare Q0 MSBs Compare I1 LSBs Compare I1 MSBs Compare Q1 LSBs
0x68 0x69 0x6A 0x6B 0x6C 0x6D 0x6E
0xB6 0x7A 0x45 0xEA 0x16 0x1A 0xC6
Rev. 0 | Page 20 of 56
AD9125
Register Name Compare Q1 MSBs SED I LSBs SED I MSBs SED Q LSBs SED Q MSBs Die Revsion Addr (Hex) 0x6F 0x70 0x71 0x72 0x73 0x7F Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Compare Value Q1[15:8] Errors detected I_BITS[7:0] Errors detected I_BITS[15:8] Errors detected Q_BITS[7:0] Errors detected Q_BITS[15:8] Revision[3:0] Bit 2 Bit 1 Bit 0 Default 0xAA 0x00 0x00 0x00 0x00 0x0C
DEVICE CONFIGURATION REGISTER DESCRIPTIONS
Table 11. Device Configuration Register Descriptions
Register Name Comm Address (Hex) 0x00 Bits 7 Name SDIO Description SDIO operation. 0 = SDIO operates as an input only. 1 = SDIO operates as a bidirectional input/output. Serial port communication LSB or MSB first. 0 = MSB first. 1 = LSB first. 1 = device is held in reset when this bit is written high and is held there until the bit is written low. 1 = powers down DAC I. 1 = powers down DAC Q. 1 = powers down the input data receiver. 1 = powers down the auxiliary ADC for temperature sensor. 1 = PLL is locked. 0 = input data is in twos complement format. 1 = input data is in binary format. Indicates I/Q data pairing on data input. 0 = I data sent to data receiver first. 1 = Q data sent to data receiver first. Swaps the bit order of the data input port. 0 = order of the data bits corresponds to the pin descriptions. 1 = bit designations are swapped; most significant bits become the least significant bits. Data receiver interface mode. 00 = dual-word mode; 32-bit interface bus width. 01 = word mode; 16-bit interleaved interface bus width. 10 = byte mode; 8-bit interleaved interface bus width. 11 = invalid. See the CMOS Input Data Ports section for details on the operation of the different interface modes. 1 = enables interrupt for PLL lock lost. 1 = enables interrupt for PLL lock. 1 = enables interrupt for sync signal lock lost. 1 = enables interrupt for sync signal lock. 1 = enables interrupt for clock generation ready. 1 = enables interrupt for soft FIFO reset. Default 0
6
LSB_FIRST
0
5 Power Control 0x01 7 6 5 4 0 7 6
Reset Power-down DAC I Power-down DAC Q Power-down data receiver Power-down auxiliary ADC PLL lock status Binary data format Q data first
0 0 0 0 0 0 0 0
Data Format
0x03
5
MSB swap
0
[1:0]
Data bus width
0
Interrupt Enable 1
0x04
7 6 5 4 3 2
Enable PLL lock lost Enable PLL lock Enable sync signal lost Enable sync signal lock Enable sync phase locked Enable soft FIFO sync
0 0 0 0 0 0
Rev. 0 | Page 21 of 56
AD9125
Register Name Address (Hex) Bits 1 0 7 6 5 4 3 2 1 0 7 Name Enable FIFO Warning 1 Enable FIFO Warning 2 Set to 0 Set to 0 Set to 0 Enable AED comparison pass Enable AED comparison fail Enable SED comparison fail Set to 0 Set to 0 PLL lock lost Description 1 = enables interrupt for FIFO Warning 1. 1 = enables interrupt for FIFO Warning 2. Set this bit to 0. Set this bit to 0. Set this bit to 0. 1 = enables interrupt for AED comparison pass. 1 = enables interrupt for AED comparison fail. 1 = enables interrupt for SED comparison fail. Set this bit to 0. Set this bit to 0. 1 = indicates that the PLL, which had been previously locked, has unlocked from the reference signal. This is a latched signal. 1 = indicates that the PLL has locked to the reference clock input. 1 = indicates that the sync logic, which had been previously locked, has lost alignment. This is a latched signal. 1 = indicates that the sync logic did achieve sync alignment. This is indicated when no phase changes were requested for at least a few full averaging cycles. 1 = indicates that the internal digital clock generation logic is ready. This occurs when internal clocks are present and stable. 1 = indicates that a FIFO reset originating from a serial port-based request has successfully completed. This is a latched signal. 1 = indicates that the difference between the FIFO read and write pointers is 1. 1 = indicates that the difference between the FIFO read and write pointers is 2. 1 = indicates that the SED logic detected a valid input data pattern compared with the preprogrammed expected values. This is a latched signal. 1 = indicates that the SED logic detected an invalid input data pattern compared with the preprogrammed expected values. This is a latched signal that automatically clears when eight valid I/Q data pairs are received. 1 = indicates that the SED logic detected an invalid input data pattern compared with the preprogrammed expected values. This is a latched signal. 1 = enables duty-cycle correction on the DACCLK input. 1 = enables duty-cycle correction on the REFCLK input. 1 = enables differential crossing correction on the DACCLK input. 1 = enables differential crossing correction on the REFCLK input. Default 0 0 0 0 0 0 0 0 0 0 0
Interrupt Enable 2
0x05
Event Flag 1 1
0x06
6 5
PLL locked Sync signal lost
0 0
4
Sync signal locked
0
3
Sync phase locked
0
2
Soft FIFO sync
0
1 0 Event Flag 21 0x07 4
FIFO Warning 1 FIFO Warning 2 AED comparison pass
0 0 0
3
AED comparison fail
0
2
SED comparison fail
Clock Receiver Control
0x08
7 6 5 4
DACCLK duty correction REFCLK duty correction DACCLK cross-correction REFCLK cross-correction
0 0 1 1
Rev. 0 | Page 22 of 56
AD9125
Register Name PLL Control 1 Address (Hex) 0x0A Bits 7 6 Name PLL enable PLL manual enable Description 1 = enables the PLL clock multiplier. REFCLK input is used as the PLL reference clock signal. Enables the manual selection of the VCO band. 1 = manual mode; the correct VCO band must be determined by the user. Selects the VCO band to be used. Selects the PLL loop filter bandwidth. 000 = loop bandwidth is nominally 200 kHz 010 = loop bandwidth is nominally 450 kHz 100 = loop bandwidth is nominally 950 kHz 110 = loop bandwidth is nominally 2 MHz Sets the nominal PLL charge-pump current. 00000 = lowest current setting. 11111 = highest current setting. PLL control clock divider. These bits determine the ratio of the DACCLK rate to the PLL controller clock rate. fPC_CLK must always be less than 80 MHz. 00 = fDACCLK/fPC_CLK = 2. 01 = fDACCLK/fPC_CLK = 4. 10 = fDACCLK/fPC_CLK = 8. 11 = fDACCLK/fPC_CLK = 16. Enables PLL cross-point controller. PLL VCO divider. These bits determine the ratio of the VCO output to the DACCLK frequencies. 00 = fVCO/fDACCLK = 1. 01 = fVCO/fDACCLK = 2. 10 = fVCO/fDACCLK = 4. 11 = fVCO/fDACCLK = 4. PLL loop divider. These bits determine the ratio of the DACCLK to the REFCLK frequencies. 00 = fDACCLK/fREFCLK = 2. 01 = fDACCLK/fREFCLK = 4. 10 = fDACCLK/fREFCLK = 8. 11 = fDACCLK/fREFCLK = 16. The PLL generated clock is tracking the REFCLK input signal. VCO control voltage readback (see Table 25). Indicates the VCO band currently selected. 1 = enables the synchronization logic. 0 = operates the synchronization at the FIFO reset rate. 1 = operates the synchronization at the data rate. 0 = sync is initiated on the falling edge of the sync input. 1 = sync is initiated on the rising edge of the sync input. Sets the number of input samples that are averaged for determining the sync phase. 000 = 1. 001 = 2. 010 = 4. 011 = 8. 100 = 16. 101 = 32. Default 0 1
PLL Control 2
0x0C
[5:0] [7:5]
Manual VCO band PLL loop bandwidth[2:0]
0 110
[4:0]
PLL charge pump current[4:0] N2[1:0]
10001
PLL Control 3
0x0D
[7:6]
3
4 [3:2]
PLL cross control enable N0[1:0]
1 10
[1:0]
N1[1:0]
01
PLL Status 1
0x0E
7 [3:0]
PLL lock VCO control voltage[3:0] VCO band readback[5:0] Sync enable Data/FIFO rate toggle Rising edge sync Sync averaging[2:0]
R R R 0 1 1 0
PLL Status 2 Sync Control 1
0x0F 0x10
[5:0] 7 6 3 [2:0]
Rev. 0 | Page 23 of 56
AD9125
Register Name Address (Hex) Bits Name Description 110 = 64. 111 = 128. This sets the requested clock phase offset after sync. The offset unit is in DACCLK cycles. This enables repositioning of the DAC output with respect to the sync input. The offset can also be used to skew the DAC outputs between the synchronized DACs. 000000 = 0 DACCLK cycles. 000001 = 1 DACCLK cycle. ... 111111 = 63 DACCLK cycles. 1 = indicates that synchronization had been attained but was subsequently lost. 1 = indicates that synchronization has been attained. Indicates the averaged sync phase offset (6.2 format). If the value differs from the requested sync phase value, this indicates sync timing errors. 00000000 = 0.0. 00000001 = 0.25. ... 11111110 = 63.50. 11111111 = 63.75. FIFO write pointer phase offset following FIFO reset. This is the difference between the read pointer and the write pointer values upon FIFO reset. The optimal value is nominally 4. 000 = 0. 001 = 1. ... 111 = 7. FIFO read and write pointers within 1. FIFO read and write pointers within 2. FIFO read and write pointers are aligned after a serial port initiated FIFO reset. Request FIFO read and write pointers alignment via the serial port. FIFO read and write pointers aligned after a hardware reset. Thermometer encoded measure of the FIFO level. 1 = bypasses fS/2 premodulator. 1 = bypasses inverse sinc filter. 1 = bypasses NCO. 0 = default. No gain scaling is applied to the NCO input to the internal digital modulator. 1 = gain scaling of 0.5 is applied to the NCO input to the internal digital modulator. This can eliminate saturation of the modulator output for some combinations of data inputs and NCO signals. 1 = bypasses phase compensation and dc offset. Default
Sync Control 2
0x11
5:0
Sync phase request[5:0]
0
Sync Status 1
0x12
7 6 [7:0]
Sync lost Sync locked Sync phase readback[7:0]
R R R
Sync Status 2
0x13
FIFO Control
0x17
[2:0]
FIFO phase offset[2:0]
4
FIFO Status 1
0x18
7 6 2 1 0
FIFO Warning 1 FIFO Warning 2 FIFO soft align acknowledge FIFO soft align request FIFO reset aligned FIFO level[7:0] Bypass premod Bypass sinc-1 Bypass NCO NCO gain
0 0
0 0 0 1 1 1 0
FIFO Status 2 Datapath Control
0x19 0x1B
[7:0] 7 6 5 3
2
Bypass phase compensation and dc offset
1
Rev. 0 | Page 24 of 56
AD9125
Register Name Address (Hex) Bits 1 Name Select sideband Description 0 = the modulator outputs high-side image. 1 = the modulator outputs low-side image. The image is spectrally inverted compared with the input data. 1 = ignores Q data from the interface and disables the clocks to the Q datapath. Sends I data to both the I and Q DACs. 00 = input signal is not modulated; filter pass band is from -0.4 to +0.4 of fIN1. 01 = input signal is not modulated; filter pass band is from 0.1 to 0.9 of fIN1. 10 = input signal is modulated by fIN1; filter pass band is from 0.6 to 1.4 of fIN1. 11 = input signal is modulated by fIN1; filter pass band is from 1.1 to 1.9 of fIN1. 1 = bypasses first-stage interpolation filter. Modulation mode for I Side Half-Band Filter 2. 000000 = input signal is not modulated; filter pass band is from -0.25 to +0.25 of fIN2. 001001 = input signal is not modulated; filter pass band is from 0.0 to 0.5 of fIN2. 010010 = input signal is not modulated; filter pass band is from 0.25 to 0.75 of fIN2. 011011 = input signal is not modulated; filter pass band is from 0.5 to 1.0 of fIN2. 100100 = input signal is modulated by fIN2; filter pass band is from 0.75 to 1.25 of fIN2. 101101 = input signal is modulated by fIN2; filter pass band is from 1.0 to 1.5 of fIN2. 110110 = input signal is modulated by fIN2; filter pass band is from 1.25 to 1.75 of fIN2. 111111 = input signal is modulated by fIN2; filter pass band is from 1.5 to 2.0 of fIN2. 1 = bypasses second stage interpolation filter. Modulation mode for I Side Half-Band Filter 3. 000000 = input signal is not modulated; filter pass band is from -0.2 to +0.2 of fIN3. 001001 = input signal is not modulated; filter pass band is from 0.05 to 0.45 of fIN3. 010010 = input signal is not modulated; filter pass band is from 0.3 to 0.7 of fIN3. 011011 = input signal is not modulated; filter pass band is from 0.55 to 0.95 of fIN3. 100100 = input signal is modulated by fIN3; filter pass band is from 0.8 to 1.2 of fIN3. 101101 = input signal is modulated by fIN3; filter pass band is from 1.05 to 1.45 of fIN3. 110110 = input signal is modulated by fIN3; filter pass band is from 1.3 to 1.7 of fIN3. 111111 = input signal is modulated by fIN3; filter pass band is from 1.55 to 1.95 of fIN3. 1 = bypasses third-stage interpolation filter. This register identifies the device as an AD9125. Default 0
0
Send I data to Q data
0
HB1 Control
0x1C
[2:1]
HB1[1:0]
0
0 HB2 Control 0x1D [6:1]
Bypass HB1 HB2[5:0]
0 0
0 HB3 Control 0x1E [6:1]
Bypass HB2 HB3[5:0]
0 0
Chip ID
0x1F
0 [7:0]
Bypass HB3 Chip ID[7:0]
0 8
Rev. 0 | Page 25 of 56
AD9125
Register Name FTW 1 (LSB) Address (Hex) 0x30 Bits [7:0] Name FTW[7:0] Description FTW[31:0] is the 32-bit frequency tuning word that determines the frequency of the complex carrier generated by the on-chip NCO. The frequency is not updated when the FTW registers are written. The values are only updated when Bit 0 of Register 0x36 transitions from 0 to 1. See Register 0x30. See Register 0x30. See Register 0x30. NCO phase offset[15:0] sets the phase of the complex carrier signal when the NCO is reset. The phase offset spans between 0 and 360. Each bit represents an offset of 0.0055. The value is in twos complement format. See Register 0x34. 1 = indicates that the NCO has been reset due to an extended FRAME pulse signal. 0 1 = the NCO is reset on the first extended FRAME pulse after this bit transitions from 0 to 1. 1 = indicates that the FTW has been updated. 0 1 = the FTW is updated on 0-to-1 transition of this bit. I phase adjust[9:0] is used to insert a phase offset between the I and Q datapaths. This can be used to correct for phase imbalance in a quadrature modulator. See the Quadrature Phase Correction section for details. Register 0x38. Q phase adjust[9:0] is used to insert a phase offset between the I and Q datapaths. This can be used to correct for phase imbalance in a quadrature modulator. See the Quadrature Phase Correction section for details. See Register 0x3A. I DAC offset[15:0] is a value added directly to the samples written to the I DAC. See Register 0x3C. Q DAC offset[15:0] is a value added directly to the samples written to the Q DAC. See Register 0x3E. I DAC FS adjust[9:0] sets the full-scale current of the I DAC. The full-scale current can be adjusted from 8.64 mA to 31.6 mA in step sizes of approximately 22.5 A. 0x000 = 8.64 mA. ... 0x200 = 20.14 mA. ... 0x3FF = 31.66 mA. 1 = puts the I-channel DAC into sleep mode (fast wakeup mode). See Register 0x40. I aux DAC[9:0] sets the magnitude of the auxiliary DAC current. The range is 0 mA to 2 mA, and the step size is 2 A. 0x000 = 0.000 mA. 0x001 = 0.002 mA. ... 0x3FF = 2.046 mA. Default 0
FTW 2 FTW 3 FTW 4 (MSB) NCO Phase Offset LSB
0x31 0x32 0x33 0x34
[7:0] [7:0] [7:0] [7:0]
FTW[15:8] FTW[23:16] FTW[31:24] NCO phase offset[7:0]
0 0 0 0
NCO Phase Offset MSB NCO FTW Update
0x35 0x36
[7:0] 5 4 1 0 [7:0]
NCO phase offset[15:8] FRAME FTW acknowledge FRAME FTW request Update FTW acknowledge Update FTW request I phase adjust[7:0]
0 0 0 0 0 0
I Phase Adj LSB
0x38
I Phase Adj MSB Q Phase Adj LSB
0x39 0x3A
[1:0] [7:0]
I phase adjust[9:8] Q phase adjust[7:0]
0 0
Q Phase Adj MSB I DAC Offset LSB I DAC Offset MSB Q DAC Offset LSB Q DAC Offset MSB I DAC FS Adjust
0x3B 0x3C 0x3D 0x3E 0x3F 0x40
[1:0] [7:0] [7:0] [7:0] [7:0] [7:0]
Q phase adjust[9:8] I DAC offset[7:0] I DAC offset[15:8] Q DAC offset[7:0] Q DAC offset[15:8] I DAC FS adjust[7:0]
0 0 0 0 0 F9
I DAC Control
0x41
7 [1:0] [7:0]
I DAC sleep I DAC FS adjust[9:8] I aux DAC[7:0]
0 1 0
Aux DAC I Data
0x42
Rev. 0 | Page 26 of 56
AD9125
Register Name I Aux DAC Control Address (Hex) 0x43 Bits 7 Name I aux DAC sign Description 0 = the auxiliary DAC I sign is positive, and the current is directed to the IOUT1P pin (Pin 67). 1 = the auxiliary DAC I sign is negative, and the current is directed to the IOUT1N pin (Pin 66). 0 = the auxiliary DAC I sources current. 1 = the auxiliary DAC I sinks current. I channel auxiliary DAC sleep. See Register 0x42. Q DAC FS adjust[9:0] sets the full-scale current of the I DAC. The full-scale current can be adjusted from 8.64 mA to 31.6 mA in step sizes of approximately 22.5 A. 0x000 = 8.64 mA. ... 0x200 = 20.14 mA. ... 0x3FF = 31.66 mA. 1 = puts the Q-channel DAC into sleep mode (fast wakeup mode). See Register 0x44. Q aux DAC[9:0] sets the magnitude of the aux DAC current. The range is 0 mA to 2 mA, and the step size is 2 A. 0x000 = 0.000 mA. 0x001 = 0.002 mA. ... 0x3FF = 2.046 mA. 0 = the auxiliary DAC Q sign is positive, and the current is directed to the IOUT2P pin (Pin 58). 1 = the auxiliary DAC Q sign is negative, and the current is directed to the IOUT2N pin (Pin 59). 0 = the auxiliary DAC Q sources current. 1 = the auxiliary DAC Q sinks current. Q-channel auxiliary DAC sleep See Register 0x46. Auxiliary ADC full-scale current. 000 = lowest current. ... 111 = highest current. Auxiliary ADC reference current. 000 = lowest current. 111 = highest current. Auxiliary ADC internal capacitor value. 0 = 5 pF. 1 = 10 pF. Die Temp[15:0] indicates the approximate die temperature. 0xADCC = -39.9C. 0xC422 = 25.1C. ... 0xD8A8 = 84.8C (see the Temperature Sensor section for details). See Register 0x49. Default 0
6 5 [1:0] [7:0]
I aux DAC current direction I aux DAC sleep I Aux DAC[9:8] Q DAC FS adjust[7:0]
0 0 0 F9
Q DAC FS Adjust
0x44
Q DAC Control
0x45
7 [1:0] [7:0]
Q DAC sleep Q DAC FS adjust[9:8] Q aux DAC[7:0]
0 1 0
Aux DAC Q Data
0x46
Q Aux DAC Control
0x47
7
Q aux DAC sign
0
6 5 Die Temp Range Control 0x48 [1:0] [6:4]
Q aux DAC current direction Q aux DAC sleep Q aux DAC[9:8] FS current[2:0]
0 0 0 0
[3:1]
Reference current[2:0]
1
0
Capacitor value
0
Die Temp LSB
0x49
[7:0]
Die temp[7:0]
R
Die Temp MSB
0x4A
[7:0]
Die temp[15:8]
R
Rev. 0 | Page 27 of 56
AD9125
Register Name SED Control Address (Hex) 0x67 Bits 7 Name SED compare enable Description 1 = enables the SED circuitry. None of the flags in this register or the values in Register 0x70 through Register 0x73 are significant if the SED is not enabled. 1 = indicates an error is detected. The bit remains set until cleared. Any write to this register clears this bit to 0. 1 = enables autoclear mode. This activates Bit 1 and Bit 0 of this register and causes Register 0x70 through Register 0x73 to be autocleared whenever eight consecutive error-free sample data sets are received. 1 = indicates an error has been detected. This bit remains high until it is autocleared by the reception of eight consecutive error-free comparisons or until it is cleared by writing to this register. 1 = indicates that the last sample comparison was error free. Compare Value I0[15:0] is the word that is compared with the I0 input sample captured at the input interface. See Register 0x68. Compare Value Q0[15:0] is the word that is compared with the Q0 input sample captured at the input interface. See Register 0x6A Compare Value I1[15:0] is the word that is compared with the I1 input sample captured at the input interface. See Register 0x6C. Compare Value Q1[15:0] is the word that is compared with the Q1 input sample captured at the input interface. See Register 0x6E. Errors detected I_BITS[15:0] indicates which bits were received in error. See Register 0x70. Errors detected Q_BITS[15:0] indicates which bits were received in error. See Register 0x72. Corresponds to device die revision. Default 0
5 3
Sample error detected Autoclear enable
0 0
1
Compare fail
0
Compare I0 LSBs Compare I0 MSBs Compare Q0 LSBs Compare Q0 MSBs Compare I1 LSBs Compare I1 MSBs Compare Q1 LSBs Compare Q1 MSBs SED I LSBs SED I MSBs SED Q LSBs SED Q MSBs Die Revision
1
0x68 0x69 0x6A 0x6B 0x6C 0x6D 0x6E 0x6F 0x70 0x71 0x72 0x73 0x7F
0 [7:0] [7:0] [7:0] [7:0] [7:0] [7:0] [7:0] [7:0] [7:0] [7:0] [7:0] [7:0] [5:2]
Compare pass Compare Value I0[7:0] Compare Value I0[15:8] Compare Value Q0[7:0] Compare Value Q0[15:8] Compare Value I1[7:0] Compare Value I1[15:8] Compare Value Q1[7:0] Compare Value Q1[15:8] Errors Detected I_BITS[7:0] Errors detected I_BITS[15:8] Errors detected Q_BITS[7:0] Errors detected Q_BITS[15:8] Revision[3:0]
0 B6 7A 45 EA 16 1A C6 AA 0 0 0 0 3
All bit event flags are cleared by writing the respective bit high.
Rev. 0 | Page 28 of 56
AD9125 CMOS INPUT DATA PORTS
The AD9125 input data port consists of a data clock (DCI), data bus, and FRAME signal. The data port can be configured to operate in three modes: dual-word mode, word mode, and byte mode. In dual-word mode, I and Q data is received simultaneously on two 16-pin buses. One bus receives I datapath input words, and the other bus receives Q datapath input words. In word mode, one 16-pin bus is used to receive interleaved I and Q input words. In byte mode, an 8-pin bus is used to receive interleaved I and Q input bytes. The pin assignments of the bus in each mode is described in Table 12. Table 12. Data Bit Pin Assignments for Data Input Modes
Mode Dual Word Word Byte Data Bus Pin Assignments I data: D[31:16] Q data: D[15:0] I and Q data: D[29:28], D[25:24], D[21:20], D[17:16], D[15:14], D[11:10], D[7:6], D[3:2] I and Q data: D[21:20], D[17:16], D[15:14], D[11:10]
I AND Q DATA I1 Q1 I2
WORD MODE
In word mode, the DCI signal is supplied as a qualifying clock that is time aligned with the input data. The rising edge of the DCI signal should be aligned with the changing data of the interleaved I and Q input data stream. The FRAME signal indicates to which DAC the data is sent. When FRAME is high, data is sent to the I DAC. When FRAME is low, data is sent to the Q DAC. For 14- and 12-bit resolution devices, the two and four LSBs are not significant, respectively. The complete timing diagram is shown in Figure 43.
DCI
FRAME
Figure 43. Timing Diagram for Word Mode
BYTE MODE
In byte and word modes, a FRAME signal is required for controlling which DAC receives the data. In dual-word mode, the FRAME signal is not required because each DAC has a dedicated bus. In byte mode, the DCI signal is supplied as a qualifying clock that is time aligned with the input data. The rising edge of the DCI signal should be aligned with the changing data of the interleaved I and Q input data stream. The FRAME signal indicates to which DAC the data is sent. When FRAME is high, data is sent to the I DAC. When FRAME is low, data is sent to the Q DAC. Both bytes must be written to each datapath for proper operation. For 14- and 12-bit resolution devices, the LSBs in the second byte are not significant. The complete timing diagram is shown in Figure 44.
DCI
DUAL-WORD MODE
In dual-word mode, the DCI signal is supplied as a qualifying clock that is time aligned with the input data. The rising edge of the DCI signal should be aligned with the changing data of each of the I and Q input data streams.
DCI
I DATA
I1
I2
I3
09016-142
I AND Q Q DATA LSB
I1MSB
I1LSB
Q1MSB Q1LSB
I2MSB
I2LSB
Q2MSB Q2LSB
09016-143
Q DATA
Q1
Q2
Q3
FRAME
Figure 42. Timing Diagram for Dual-Word Mode
Figure 44. Timing Diagram for Byte Mode
Rev. 0 | Page 29 of 56
09016-144
AD9125
INTERFACE TIMING
The timing diagram for the digital interface port is shown in Figure 45. The sampling point of the data bus occurs on the falling edge of the DCI signal and has an uncertainty of 2.1 ns, as illustrated by the sampling interval shown in Figure 45. The D[31:0] and FRAME signals must be valid throughout this sampling interval. The setup (tS) and hold (tH) times with respect to the edges are shown in Figure 45. The minimum setup and hold times are shown in Table 13.
DCI
The data interface timing can be verified by using the sample error detection (SED) circuitry. See the Interface Timing Validation section for details.
FIFO OPERATION
The AD9125 contains a 2-channel, 16-bit wide, eight-word-deep FIFO designed to relax the timing relationship between the data arriving at the DAC input ports and the internal DAC data rate clock. The FIFO acts as a buffer that absorbs timing variations between the data source and DAC, such as the clock-to-data variation of an FPGA or ASIC, which significantly increases the timing budget of the interface. Figure 47 shows the block diagram of the datapath through the FIFO. The data is latched into the device and is formatted, and then it is written into the FIFO register determined by the FIFO write pointer. The value of the write pointer is incremented every time a new word is loaded into the FIFO. Meanwhile, data is read from the FIFO register determined by the read pointer and fed into the digital datapath. The value of the read pointer is updated every time data is read into the datapath from the FIFO. This happens at the data rate, that is, the DACCLK rate divided by the interpolation ratio. Valid data is transmitted through the FIFO as long as the FIFO does not overflow or become empty. Note that an overflow or empty condition of the FIFO is the same as the write pointer and read pointer being equal. When both pointers are equal, an attempt is made to read and write a single FIFO register simultaneously. This simultaneous register access leads to unreliable data transfer through the FIFO and must be avoided. Nominally, data is written to the FIFO at the same rate that data is read from the FIFO, which keeps the data level in the FIFO constant. If data is written to the FIFO faster than data is read, the data level in the FIFO increases. If data is written to the device slower than data is read, the data level in the FIFO decreases. For an optimum timing margin, the FIFO level should be maintained near half full, which is the same as maintaining a difference of four between the write pointer and read pointer values.
D[31:0]
tS
FRAME
tH
09016-146
Figure 45. Timing Diagram for Input Data Ports
Table 13. Data Port Setup and Hold Times
Minimum Setup Time, tS (ns) 0.86 Minimum Hold Time, tH (ns) 1.24
DCI
tS-FRAME tH-FRAME
09016-147
FRAME
Figure 46. Timing Diagram for Frame input
Table 14. FRAME Setup and Hold Times
Minimum Setup Time, tS-FRAME (ns) -0.04 Minimum Hold Time, tH_FRAME (ns) +1.05
32 BITS REG 0 REG 1 REG 2 DATA INPUT LATCH DATA ASSEMBLER REG 3 REG 4 REG 5 REG 6 REG 7 DCI WRITE POINTER 32 BITS
16
DATA PATHS
16
DACS
READ POINTER
/ INT
DACCLK
Figure 47. Block Diagram of Datapath Through FIFO
Rev. 0 | Page 30 of 56
09016-018
AD9125
Initializing the FIFO Data Level
To avoid a concurrent read and write to the same FIFO address and to ensure a fixed pipeline delay, it is important to initialize the FIFO pointers to known states. The FIFO pointers can be initialized in two ways: via a write sequence to the serial port or by strobing the FRAME input. There are two types of FIFO pointer resets: a relative reset and an absolute reset. A relative reset enforces a defined FIFO depth. An absolute reset enforces a particular write pointer value when the reset is initiated. A serial port initiated FIFO reset is always a relative reset. A FRAME strobe initiated reset can be either a relative or an absolute reset. The operation of the FRAME initiated FIFO reset depends on the synchronization mode chosen. When synchronization is disabled or when the device is configured for data rate mode synchronization, the FRAME strobe initiates a relative FIFO reset. When FIFO mode synchronization is chosen, the FRAME strobe initiates an absolute FIFO reset. More details on the synchronization function can be found in the Multichip Synchronization section. A summary of the synchronization modes and the type of FIFO reset employed is listed in Table 15. Table 15. Summary of FIFO Resets
FIFO Reset Signal Serial Port FRAME Synchronization Mode Disabled Data Rate FIFO Rate Relative reset Relative reset Relative reset Relative reset Relative reset Absolute reset
corresponds to one DCI period in dual-word mode, two DCI periods in word mode, and four DCI periods in byte mode. To initiate a relative FIFO reset with the FRAME signal, the device must be configured in data rate mode (Register 0x10, Bit 6). When FRAME is asserted in data rate mode, the write pointer is set to 4 (by default or to the FIFO start level) the next time the read pointer becomes 0 (see Figure 48).
READ POINTER 0 1 2 3 4 5 6 7 0 1 2 3
FRAME
FIFO WRITE RESETS
WRITE POINTER
3
4
5
6
7
0
1
2
4
5
6
7
Figure 48. FRAME Input vs. Write Pointer Value, Data Rate Mode
Write Pointer Initialization via FRAME Signal
In FIFO rate synchronization mode, the REFCLK/SYNC signal is used to reset the FIFO read pointer to 0. The edge of the DAC clock used to sample the SYNC signal is selected by Bit 3 of Register 0x10. The FRAME signal is used to reset the FIFO write pointer. In the FIFO rate synchronization mode, the FIFO write pointer is reset immediately after the FRAME signal is asserted high for at least the time interval needed to load complete data to the I and Q DACs. The FIFO write pointer is initialized to the value of the FIFO phase offset[2:0] (Register 0x17). FIFO rate synchronization is selected by setting Bit 6 of Register 0x10 to 0.
SYNC
FIFO READ RESET
FIFO Level Initialization via Serial Port
A serial port initiated FIFO reset can be issued in any mode and always results in a relative FIFO reset. To initialize the FIFO data level through the serial port, Bit 1 of Register 0x18 should be toggled from 0 to 1 and then back to 0. When the write to the register is complete, the FIFO data level is initialized. When the initialization is triggered, the next time the read pointer becomes 0, the write pointer is set to the value of the FIFO phase offset level (Register 0x17, Bits[2:0]) variable upon initialization. By default, this is 4, but it can be programmed to a value between 0 and 7. The recommended procedure for a serial port FIFO data level initialization is as follows: 1. 2. 3. 4. Request FIFO level reset by setting Register 0x18, Bit 1, to 1. Verify that the part acknowledges the request by ensuring that Register 0x18, Bit 2, is 1. Remove the request by setting Register 0x18, Bit 1, to 0. Verify that the part drops the acknowledge signal by ensuring that Register 0x18, Bit 2, is 0.
READ POINTER FRAME WRITE POINTER
0
1
2
3
4
5
6
7
0
1
2
3
FIFO WRITE RESET
FIFO PHASE OFFSET[2:0] REGISTER 0x17, BITS[2:0] = 0b101
09016-148
6
5
6
7
0
1
2
3
4
5
6
7
Figure 49. FRAME Input vs. Write Pointer Value, FIFO Rate Mode
Monitoring the FIFO Status
The FIFO initialization and status can be read from Register 0x18. This register provides information on the FIFO initialization method and whether the initialization was successful. The MSB of Register 0x18 is a FIFO warning flag that can optionally trigger a device interrupt (IRQ). This flag is an indication that the FIFO is close to emptying (FIFO level is 1) or overflowing (FIFO level is 7). This is an indication that data may soon be corrupted and action should be taken. The FIFO data level can be read from Register 0x19 at any time. The FIFO data level reported by the serial port is denoted as a 7-bit thermometer code of the write counter state relative to the absolute read counter being at 0. The optimum FIFO data level of 4 is, therefore, reported as a value of 00001111 in the status register. It should be noted that, depending on the timing relationship between DCI and the main DACCLK, the FIFO level value can be off by 1 count. Therefore, it is important to keep the difference between the read and write pointers to at least 2.
FIFO Level Initialization via FRAME Signal
The primary function of the FRAME input is indicating to which DAC the input data is written. Another function of the FRAME input is initializing the FIFO data level value. This is done by asserting the FRAME signal high for at least the time interval needed to load complete data to the I and Q DACs. This
Rev. 0 | Page 31 of 56
09016-019
AD9125 DIGITAL DATAPATH
The block diagram in Figure 50 shows the functionality of the digital datapath. The digital processing includes a premodulation block, three half-band interpolation filters, a quadrature modulator with a fine resolution NCO, a phase and offset adjustment block, and an inverse sinc filter.
PHASE AND OFFSET ADJUST
Half-Band Filter 1 (HB1)
HB1 has four modes of operation, as shown in Figure 51. The shape of the filter response is identical in each of the four modes. The four modes are distinguished by two factors: the filter center frequency and whether the input signal is modulated by the filter.
MODE 0 0 MODE 1 MODE 2 MODE 3
PREMOD
HB1
HB2
HB3
SINC-1
09016-020
-20
Figure 50. Block Diagram of Digital Datapath
The digital datapath accepts I and Q data streams and processes them as a quadrature data stream. The signal processing blocks can be used when the input data stream is represented as complex data. The datapath can be used to process an input data stream representing two independent real data streams as well, but the functionality is somewhat restricted. The premodulation block can be used, as well as any of the nonshifted interpolation filter modes (see the Premodulation section for more details).
GAIN (dB)
-40
-60
-80
-100 0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 NORMALIZED FREQUENCY (x fIN1)
09016-021
PREMODULATION
The half-band interpolation filters have selectable pass bands that allow the center frequencies to be moved in increments of 1/2 of their input data rate. The premodulation block provides a digital upconversion of the incoming waveform by 1/2 of the incoming data rate, fDATA. This can be used to frequency-shift baseband input data to the center of the interpolation filters' pass band.
Figure 51. HB1 Filter Modes
INTERPOLATION FILTERS
The transmit path contains three interpolation filters. Each of the three interpolation filters provides a 2x increase in output data rate. The half-band (HB) filters can be individually bypassed or cascaded to provide 1x, 2x, 4x, or 8x interpolation ratios. Each of the half-band filter stages offers a different combination of bandwidths and operating modes. The bandwidth of the three half-band filters with respect to the data rate at the filter input is as follows: * * * Bandwidth of HB1 = 0.8 x fIN1 Bandwidth of HB2 = 0.5 x fIN2 Bandwidth of HB3 = 0.4 x fIN3
As shown in Figure 51, the center frequency in each mode is offset by 1/2 the input data rate (fIN1) of the filter. Mode 0 and Mode 1 do not modulate the input signal. Mode 2 and Mode 3 modulate the input signal by fIN1. When HB1 operates in Mode 0 and Mode 2, the I and Q paths operate independently and no mixing of the data between channels occurs. When HB1 operates in Mode 1 and Mode 3, mixing of the data between the I and Q paths occurs; therefore, the data input into the filter is assumed complex. Table 16 summarizes the HB1 modes. Table 16. HB1 Filter Mode Summary
Mode 0 1 2 3 fCENTER DC fIN/2 fIN 3fIN/2 fMOD None None fIN fIN Input Data Real or complex Complex Real or complex Complex
The usable bandwidth is defined as the frequency over which the filters have a pass-band ripple of less than 0.001 dB and an image rejection of greater than +85 dB. As is discussed in the Half-Band Filter 1 (HB1) section, the image rejection usually sets the usable bandwidth of the filter, not the pass-band flatness. The half-band filters operate in several modes, providing programmable pass-band center frequencies as well as signal modulation. The HB1 filter has four modes of operation, and the HB2 and HB3 filters each have eight modes of operation.
Rev. 0 | Page 32 of 56
AD9125
Figure 52 shows the pass-band filter response for HB1. In most applications, the usable bandwidth of the filter is limited by the image suppression provided by the stop-band rejection, not by the pass-band flatness. Table 17 shows the pass-band flatness and stop-band rejection that the HB1 filter supports at different bandwidths.
0.02 0 0 -20 -0.02
GAIN (dB) GAIN (dB)
Half-Band Filter 2 (HB2)
HB2 has eight modes of operation, as shown in Figure 53 and Figure 54. The shape of the filter response is identical in each of the eight modes. The eight modes are distinguished by two factors: the filter center frequency and whether the input signal is modulated by the filter.
MODE 0 MODE 2 MODE 4 MODE 6
-40
-0.04
-60 -0.06 -80
-0.08
0
0.04 0.08 0.12 0.16 0.20 0.24 0.28 0.32 0.36 0.40 NORMALIZED FREQUENCY (x fIN1)
09016-022
0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
1.8
2.0
NORMALIZED FREQUENCY (x fIN2)
Figure 52. Pass-Band Detail of HB1
Figure 53. HB2, Even Filter Modes
MODE 1 0 MODE 3 MODE 5 MODE 7
Table 17. HB1 Pass-Band Flatness and Stop-Band Rejection
Bandwidth (% of fIN1) 80 80.4 81.2 82.0 83.6 85.6 Pass-Band Flatness (dB) 0.001 0.0012 0.0033 0.0076 0.0271 0.1096 Stop-Band Rejection (dB) 85 80 70 60 50 40
-20
GAIN (dB)
-40
-60
-80
-100 0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 NORMALIZED FREQUENCY (x fIN2)
09016-024
Figure 54. HB2, Odd Filter Modes
As shown in Figure 53 and Figure 54, the center frequency in each mode is offset by 1/4 of the input data rate (fIN2) of the filter. Mode 0 through Mode 3 do not modulate the input signal. Mode 4 through Mode 7 modulate the input signal by fIN2. When HB2 operates in Mode 0 and Mode 4, the I and Q paths operate independently and no mixing of the data between channels occurs. When HB2 operates in the other six modes, mixing of the data between the I and Q paths occurs; therefore, the data input to the filter is assumed complex.
Rev. 0 | Page 33 of 56
09016-023
-0.10
-100
AD9125
Table 18 summarizes the HB2 and HB3 modes. Table 18. HB2 and HB3 Filter Mode Summary
Mode 0 1 2 3 4 5 6 7 fCENTER DC fIN/4 fIN/2 3fIN/4 fIN 5fIN/4 6fIN/4 7fIN/4 fMOD None None None None fIN fIN fIN fIN Input Data Real or complex Complex Complex Complex Real or complex Complex Complex Complex
Half-Band Filter 3 (HB3)
HB3 has eight modes of operation that function the same as HB2. The primary difference between HB2 and HB3 is the filter bandwidths. Figure 56 shows the pass-band filter response for HB3. In most applications, the usable bandwidth of the filter is limited by the image suppression provided by the stop-band rejection, not by the pass-band flatness. Table 20 shows the pass-band flatness and stop-band rejection that the HB3 filter supports at different bandwidths.
0.02
Figure 55 shows the pass-band filter response for HB2. In most applications, the usable bandwidth of the filter is limited by the image suppression provided by the stop-band rejection, not by the pass-band flatness. Table 19 shows the pass-band flatness and stop-band rejection that the HB2 filter supports at different bandwidths.
0.02
0
-0.02
GAIN (dB)
-0.04
-0.06
-0.08 0 -0.10 -0.02
GAIN (dB)
0
0.04
0.08
0.12
0.16
0.20
0.24
0.28
NORMALIZED FREQUENCY (x fIN3) -0.04
Figure 56. Pass-Band Detail of HB3
-0.06
Table 20. HB3 Pass-Band Flatness and Stop-Band Rejection
Complex Bandwidth (% of fIN3) 40 40.8 42.4 45.6 49.8 55.6 Pass-Band Flatness (dB) 0.001 0.0014 0.002 0.0093 0.03 0.1 Stop-Band Rejection (dB) 85 80 70 60 50 40
-0.08
-0.10 0 0.04 0.08 0.12 0.16 0.20 0.24 0.28 0.32 NORMALIZED FREQUENCY (x fIN2)
09016-025
Figure 55. Pass-Band Detail of HB2
Table 19. HB2 Pass-Band Flatness and Stop-Band Rejection
Complex Bandwidth (% of fIN2) 50 50.8 52.8 56.0 60 64.8 Pass-Band Flatness (dB) 0.001 0.0012 0.0028 0.0089 0.0287 0.1877 Stop-Band Rejection (dB) 85 80 70 60 50 40
Rev. 0 | Page 34 of 56
09016-026
AD9125
NCO MODULATION
The digital quadrature modulator makes use of a numerically controlled oscillator, a phase shifter, and a complex modulator to provide a means for modulating the signal by a programmable carrier signal. A block diagram of the digital modulator is shown in Figure 57. The fine modulation provided by the digital modulator, in conjunction with the coarse modulation of the interpolation filters and premodulation block, allows the signal to be placed anywhere in the output spectrum with very fine frequency resolution.
I DATA INTERPOLATION
DATAPATH CONFIGURATION
Configuring the AD9125 datapath starts with the application requirements of the input data rate, the interpolation ratio, the output signal bandwidth, and the output signal center frequency. Given these four parameters, the first step in configuring the datapath is to verify that the device supports the bandwidth requirements. The modes of the interpolation filters are then chosen. Finally, any additional frequency offset requirements are determined and applied with premodulation and NCO modulation.
Determining Datapath Signal Bandwidth
The available signal bandwidth of the datapath is dependent on the center frequency of the output signal in relation to the center frequency of the interpolation filters used. Signal center frequencies that are offset from the center frequencies of the half-band filters lower the available signal bandwidth. When correctly configured, the available complex signal bandwidth for 2x interpolation is always 80% of the input data rate. The available signal bandwidth for 4x interpolation vs. output frequency varies between 50% and 80% of the input data rate, as shown in Figure 58. Note that in 4x interpolation mode, fDAC = 4 x fDATA; therefore, the data shown in Figure 58 repeats four times from dc to fDAC.
HB1 AND HB2 0.8 BANDWIDTH/fDATA
COSINE FTW[31:0] NCO PHASE OFFSET [15:0]
NCO
SINE - + -1
I OUTPUT Q OUTPUT
SPECTRAL INVERSION
0
1
Q DATA
INTERPOLATION
Figure 57. Digital Quadrature Modulator Block Diagram
The quadrature modulator is used to mix the carrier signal generated by the NCO with the I and Q signal. The NCO produces a quadrature carrier signal to translate the input signal to a new center frequency. A complex carrier signal is a pair of sinusoidal waveforms of the same frequency, offset 90 from each other. The frequency of the complex carrier signal is set via FTW[31:0] in Register 0x30 through Register 0x33. The NCO operating frequency, fNCO, is at either fDATA (HB1 bypassed) or twice fDATA (HB1 enabled). The frequency of the complex carrier signal can be set from dc up to fNCO. The frequency tuning word (FTW) is calculated as
09016-027
0.5 HB2 AND HB3 0.3
0.2
0.4
0.6
0.8
1.0
fOUT/fDATA
f FTW = CARRIER x 2 32 f NCO The generated quadrature carrier signal is mixed with the I and Q data. The quadrature products are then summed into the I and Q datapaths, as shown in Figure 57.
Figure 58. Signal Bandwidth vs. Center Frequency of the Output Signal, 4x Interpolation
Configuring 4x interpolation using the HB2 and HB3 filters can lower the power consumption of the device at the expense of reduced bandwidth. The lower curve in Figure 58 shows that the supported bandwidth in this mode varies from 30% to 50% of fDATA. The available signal bandwidth for 8x interpolation vs. output frequency varies between 50% and 80% of the input data rate, as shown in Figure 59. Note that in 8x interpolation mode, fDAC = 8 x fDATA; therefore, the data shown in Figure 59 repeats eight times from dc to fDAC.
Updating the Frequency Tuning Word
The frequency tuning word registers do not update immediately upon writing as other configuration registers. After loading the FTW registers with the desired values, Bit 0 of Register 0x36 must transition from 0 to 1 for the new FTW to take effect.
Rev. 0 | Page 35 of 56
09016-028
AD9125
HB1, HB2, AND HB3 0.8
DETERMINING INTERPOLATION FILTER MODES
Table 21 shows the recommended interpolation filter settings for a variety of filter interpolation factors, filter center frequencies, and signal modulation. The interpolation modes were chosen based on the final center frequency of the signal and by determining the frequency shift of the signal required. When these are known and put in terms of the input data rate (fDATA), the filter configuration that comes closest to matching should be chosen from Table 21.
BANDWIDTH/fDATA
0.6 0.5
0.25
0.50
0.75
1.00
fOUT/fDATA
Figure 59. Signal Bandwidth vs. Center Frequency of the Output Signal, 8x Interpolation
Table 21. Recommended Interpolation Filter Modes (Register 0x1C through Register 0x1E)
Interpolation Factor 8 8 82 8 8 8 8 8 8 8 8 8 8 8 8 8 4 43 4 4 4 4 4 4 2 2 2 2
1
HB1[1:0] 00 (0) 01 (1) 10 (2) 11 (3) 00 (0) 01 (1) 10 (2) 11 (3) 00 (0) 01 (1) 10 (2) 11 (3) 00 (0) 01 (1) 10 (2) 11 (3) 00 (0) 01 (1) 10 (2) 11 (3) 00 (0) 01 (1) 10 (2) 11 (3) 00 (0) 01 (1) 10 (2) 11 (3)
Filter Modes HB2[5:0] 000000 001001 010010 011011 100100 101101 110110 111111 000000 001001 010010 011011 100100 101101 110110 111111 000000 001001 010010 011011 100100 101101 110110 111111 Bypass Bypass Bypass Bypass
09016-029
0.1
0.4
0.6
0.9
HB3[5:0] 000000 000000 001001 001001 010010 010010 011011 011011 100100 100100 101101 101101 110110 110110 111111 111111 Bypass Bypass Bypass Bypass Bypass Bypass Bypass Bypass Bypass Bypass Bypass Bypass
fSIGNAL Modulation DC DC 1 fDATA fDATA1 2 x fDATA 2 x fDATA1 3 x fDATA 3 x fDATA1 4 x fDATA 4 x fDATA1 5 x fDATA 5 x fDATA1 6 x fDATA 6 x fDATA1 7 x fDATA 7 x fDATA1 DC DC1 fDATA fDATA1 2 x fDATA 2 x fDATA1 3 x fDATA 3 x fDATA1 DC DC1 fDATA fDATA1
fCENTER Shift 0 fDATA/2 fDATA 3 x fDATA/2 2 x fDATA 5 x fDATA/2 3 x fDATA 7 x fDATA/2 4 x fDATA 9 x fDATA/2 5 x fDATA 11 x fDATA/2 6 x fDATA 13 x fDATA/2 7 x fDATA 15 x fDATA/2 0 fDATA/2 fDATA 3 x fDATA/2 2 x fDATA 5 x fDATA/2 3 x fDATA 7 x fDATA/2 0 fDATA/2 fDATA 3 x fDATA/2
When HB1 Mode 1 or Mode 3 is used, enabling premodulation provides an addition frequency translation of the input signal by fDATA/2, which centers a baseband input signal in the filter pass band. 2 This configuration was used in the 8x interpolation without NCO example. In addition, see the 8x Interpolation Without NCO section. 3 This configuration was used in the 4x interpolation with NCO example. In addition, see the 4x Interpolation with NCO section
Rev. 0 | Page 36 of 56
AD9125
DATAPATH CONFIGURATION EXAMPLE
8x Interpolation Without NCO
Given the following conditions, the desired 75 MHz of bandwidth is 75% of fDATA: * * * * fDATA = 100 MSPS 8x interpolation fBW = 75 MHz fCENTER = 100 MHz
4x Interpolation with NCO
Given the following conditions, the desired 140 MHz of bandwidth is 56% of fDATA: * * * * fDATA = 250 MSPS 4x interpolation fBW = 140 MHz fCENTER = 175 MHz
In this case, the ratio of fOUT/fDATA = 100/100 = 1.0. From Figure 59, the bandwidth supported at fDATA is 0.8, which verifies that the AD9125 supports the bandwidth required in this configuration. The signal center frequency is fDATA, and assuming the input signal is at baseband, the frequency shift required is also fDATA. Using the settings detailed in the third row of the IF column from Table 21 (these settings use the configuration in the 8x interpolation without NCO example) selects filter modes that result in a center frequency of fDATA and a frequency translation of fDATA. The selected modes for the three half-band filters are HB1, Mode 2; HB2, Mode 2; and HB3, Mode 1. Figure 60 shows how the signal propagates through the interpolation filters. Because 2 x fIN1 = fIN2 and 2 x fIN2 = fIN3, the signal appears frequency scaled by 1/2 into each consecutive stage. The output signal band spans 0.15 to 0.35 of fIN3 (400 MHz). Therefore, the output frequency supported is 60 MHz to 140 MHz, which covers the 75 MHz bandwidth centered at 100 MHz, as desired.
As shown in Figure 58, the value at 0.7 x fDATA is 0.6. This is calculated as 0.8 - 2(0.7 - 0.6) = 0.6. Therefore, the AD9125 supports a bandwidth of 60% of fDATA, which exceeds the required 56%. The signal center frequency is 0.7 x fDATA, and assuming the input signal is at baseband, the frequency shift required is also 0.7 x fDATA. Using the settings detailed in the second row in the IF column in the 4x interpolation section in Table 21 selects the filter modes that give a center frequency of fDATA/2 and no frequency translation. The selected modes for the three halfband filters are HB1, Mode 1; HB2, Mode 1; and HB3, bypassed. Because Mode 1 of HB1 was selected, the premodulation block should be enabled. This provides fDATA/2 modulation, which centers the baseband input data at the center frequency of HB1. The digital modulator can be used to provide the final frequency translation of 0.2 x fDATA to place the output signal at 0.7 x fDATA, as desired. The formula for calculating the FTW of the NCO is FTW = f CARRIER x 2 32 f NCO
where: fCARRIER = 0.2 x fDATA. fNCO = 2 x fDATA. Therefore, FTW = 232/10.
0
1
2
3
0
HB1
0.1
0.4
0.6
-0.5
0
0.5
1.0
1.5
2.0 x fIN1
HB2
0
1 2
3
4
5 6
7
0.25
0.75
1.25
1.75
-0.5
0
0.3
0.5
0.7
1.0
1.5
2.0 x fIN2
0
1 2
3
HB3
4
5 6
7
-0.2
0.2 0.3
0.7
0.15
0.35
Figure 60. Signal Propagation for 8x Interpolation (fDATA Modulation)
Rev. 0 | Page 37 of 56
09016-030
-0.5
0
0.5
1.0
1.5
2.0 x fIN3
AD9125
DATA RATES VS. INTERPOLATION MODES
Table 23 summarizes the maximum bus speed (fBUS), the supported input data rates, and the signal bandwidths for various combinations of bus width modes and interpolation rates. The maximum bus speed in any mode is 250 MHz. The maximum DAC update rate (fDAC) in any mode is 1000 MHz. The real signal bandwidth supported is a fraction of the input data rate, which depends on the interpolation filter (HB1, HB2, or HB3) selected. The complex signal bandwidth supported is twice the real signal bandwidth. In general, 2x interpolation is best supported by enabling HB1, and 4x interpolation is best supported enabling HB1 and HB2. In some cases, power dissipation can be lowered by avoiding HB1. If the bandwidth required is low enough, 2x interpolation can be supported by using HB2, and 4x interpolation can be supported by using HB2 and HB3. In practice, this modulation results in mixing functions as shown in Table 22.
Table 22. Modulation Mixing Sequences
Modulation fS/2 fS/4 3 x fS/4 fS/8 Mixing Sequence I = I, -I, I, -I, ... Q = Q, -Q, Q, -Q, ... I = I, Q, -I, -Q, ... Q = Q, -I, -Q, I, ... I = I, -Q, -I, Q, ... Q = Q, I, -Q, -I, ... I = I, r(I + Q), Q, r(-I + Q), -I, -r(I + Q), -Q, r(I - Q), ... Q = Q, r(Q - I), -I, -r(Q + I), -Q, r(-Q + I),I, r(Q + I), ...
Note that r =
2 2
COARSE MODULATION MIXING SEQUENCES
The coarse digital quadrature modulation occurs within the interpolation filters. The modulation shifts the frequency spectrum of the incoming data by the frequency offset selected. The frequency offsets available are multiples of the input data rate. The modulation is equivalent to multiplying the quadrature input signal by a complex carrier signal, C(t), of the form
C(t) = cos(ct) + j sin(ct)
As shown in Table 22, the mixing functions of most of the modes result in cross coupling samples between the I and Q channels. The I and Q channels only operate independently in fS/2 mode. This means that real modulation using both the I and Q DAC outputs can only be done in fS/2 mode. All other modulation modes require complex input data and produce complex output signals.
Table 23. Summary of Data Rates and Bandwidths vs. Interpolation Modes
Bus Width Byte Mode (8 Bits) HB3 0 0 0 0 1 1 0 0 0 0 1 1 0 0 0 0 1 1 Filter Modes HB2 HB1 0 0 0 1 1 0 1 1 1 0 1 1 0 0 0 1 1 0 1 1 1 0 1 1 0 0 0 1 1 0 1 1 1 0 1 1 fBUS (Mbps) 250 250 250 250 250 250 250 250 250 250 250 250 250 250 250 250 250 125 fDATA (Mbps) 62.5 62.5 62.5 62.5 62.5 62.5 125 125 125 125 125 125 250 250 250 250 250 125 Real Signal Bandwidth (MHz) 31.25 25 15.625 25 15.625 25 62.5 50 31.25 50 31.25 50 125 100 62.5 100 62.5 50 fDAC (MHz) 62.5 125 125 250 250 500 125 250 250 500 500 1000 250 500 500 1000 1000 1000
Word Mode (16 Bits)
Dual-Word Mode (32 Bits)
Rev. 0 | Page 38 of 56
AD9125
QUADRATURE PHASE CORRECTION
The purpose of the quadrature phase correction block is to enable compensation of the phase imbalance of the analog quadrature modulator following the DAC. If the quadrature modulator has a phase imbalance, the unwanted sideband appears with significant energy. Tuning the quadrature phase adjust value can optimize image rejection in single sideband radios. Ordinarily, the I and Q channels have an angle of precisely 90 between them. The quadrature phase adjustment is used to change the angle between the I and Q channels. When the I phase adjust[9:0] is set to 1000000000, the I DAC output moves approximately 1.75 away from the Q DAC output, creating an angle of 91.75 between the channels. When the I phase adjust[9:0] is set to 0111111111, the I DAC output moves approximately 1.75 toward the Q DAC output, creating an angle of 88.25 between the channels. The Q phase adjust bits (Bits[9:0]) work in a similar fashion. When the Q phase adjust[9:0]) is set to 1000000000, the Q DAC output moves approximately 1.75 away from the I DAC output, creating an angle of 91.75 between the channels. When the Q phase adjust[9:0] is set to 0111111111, the Q DAC output moves approximately 1.75 toward the I DAC output, creating an angle of 88.25 between the channels. Based on these two endpoints, the combined resolution of the phase compensation register is approximately 3.5/1024, or 0.00342, per code.
MAGNITUDE (dB)
20
0
15 IOUTxP (mA)
5 IOUTxN (mA)
09016-032 09016-031
10
10
5
15
0 0x0000
0x4000
0x8000 DAC OFFSET VALUE
0xC000
20 0xFFFF
Figure 61. DAC Output Currents vs. DAC Offset Value
INVERSE SINC FILTER
The inverse sinc (sinc-1) filter is a nine-tap FIR filter. The composite response of the sinc-1 and the sin(x)/x response of the DAC is shown in Figure 62. The composite response has less than 0.05 dB pass-band ripple up to a frequency of 0.4 x fDACCLK. To provide the necessary peaking at the upper end of the pass band, the inverse sinc filters have an intrinsic insertion loss of about 3.2 dB. Figure 62 shows the composite frequency response.
-3.0
-3.2
DC OFFSET CORRECTION
The dc value of the I datapath and the Q datapath can be independently controlled by adjusting the I DAC offset[15:0] and Q DAC offset[15:0] values in Register 0x3C through Register 0x3F. These values are added directly to the datapath values. Care should be taken not to overrange the transmitted values. Figure 61 shows how the DAC offset current varies as a function of the I DAC offset[15:0] and Q DAC offset[15:0] values. With the digital inputs fixed at midscale (0x0000, twos complement data format), Figure 61 shows the nominal IOUTxP and IOUTxN currents as the DAC offset value is swept from 0 to 65,535. Because IOUTxP and IOUTxN are complementary current outputs, the sum of IOUTxP and IOUTxN is always 20 mA.
-3.4
-3.6
-3.8
-4.0 0 0.1 0.2 0.3 0.4 0.5
fOUT/fDAC
Figure 62. Sample Composite Responses of the Sinc-1 Filter with Sin(x)/x Roll-Off
The sinc-1 filter is enabled by default. It can be bypassed by setting the bypass sinc-1 bit (Register 0x1B, Bit 6).
Rev. 0 | Page 39 of 56
AD9125 DAC INPUT CLOCK CONFIGURATIONS
DAC INPUT CLOCK CONFIGURATIONS
The AD9125 DAC sample clock (DACCLK) can be sourced directly or by clock multiplying. Clock multiplying employs the on-chip phased-locked loop (PLL) that accepts a reference clock operating at a submultiple of the desired DACCLK rate, most commonly the data input frequency. The PLL then multiplies the reference clock up to the desired DACCLK frequency, which can be used to generate all the internal clocks required by the DAC. The clock multiplier provides a high quality clock that meets the performance requirements of most applications. Using the on-chip clock multiplier removes the burden of generating and distributing the high speed DACCLK. The second mode bypasses the clock multiplier circuitry and allows DACCLK to be sourced directly to the DAC core. This mode enables the user to source a very high quality clock directly to the DAC core. Sourcing the DACCLK directly through the REFCLKP, REFCLKN, DACCLKP, and DACCLKN pins may be necessary in demanding applications that require the lowest possible DAC output noise, particularly when directly synthesizing signals above 150 MHz. The minimum input drive level to either clock input is 200 mV p-p differential. The optimal performance is achieved when the clock input signal is between 800 mV p-p differential and 1.6 V p-p differential. Whether using the on-chip clock multiplier or sourcing the DACCLK directly, it is necessary that the input clock signal to the device has low jitter and fast edge rates to optimize the DAC noise performance.
Direct Clocking
Direct clocking with a low noise clock produces the lowest noise spectral density at the DAC outputs. To select the differential clock inputs as the source for the DAC sampling clock, set the PLL enable bit (Register 0x0A, Bit 7) to 0. This powers down the internal PLL clock multiplier and selects the input from the DACCLKP and DACCLKN pins as the source for the internal DAC sample clock. The device also has duty-cycle correction circuitry and differential input-level correction circuitry. Enabling these circuits can provide improved performance in some cases. The control bits for these functions can be found in Register 0x08 (see Table 11).
Clock Multiplication
The on-chip PLL clock multiplier circuit can be used to generate the DAC sample rate clock from a lower frequency reference clock. When the PLL enable bit (Register 0x0A, Bit 7) is set to 1, the clock multiplication circuit generates the DAC sample clock from the lower rate REFCLK input. The functional diagram of the clock multiplier is shown in Figure 64. The clock multiplication circuit operates such that the VCO outputs a frequency, fVCO, equal to the REFCLK input signal frequency multiplied by N1 x N0. fVCO = fREFCLK x (N1 x N0) The DAC sample clock frequency, fDACCLK, is equal to fDACCLK = fREFCLK x N1 The output frequency of the VCO must be chosen to keep fVCO in the optimal operating range of 1.0 GHz to 2.1 GHz. The frequency of the reference clock and the values of N1 and N0 must be chosen so that the desired DACCLK frequency can be synthesized and the VCO output frequency is in the correct range.
ADC REGISTER 0x0E, BITS[3:0] VCO CONTROL VOLTAGE
Driving the DACCLK and REFCLK Inputs
The REFCLK and DACCLK differential inputs share similar clock receiver input circuitry. Figure 63 shows a simplified circuit diagram of the input. The on-chip clock receiver has a differential input impedance of about 10 k. It is self-biased to a commonmode voltage of about 1.25 V. The inputs can be driven by directly coupling differential PECL or LVDS drivers. The inputs can also be ac-coupled if the driving source cannot meet the input compliance voltage of the receiver.
DACCLKP, REFCLKP 5k 1.25V
09016-033
5k DACCLKN, REFCLKN
Figure 63. Clock Receiver Input Equivalent Circuit
REGISTER 0x06, BITS[7:6] PLL LOCK LOST PLL LOCKED REFCLKP/REFCLKN (PIN 69 AND PIN 70)
PHASE DETECTION
LOOP FILTER
VCO
/N1 REGISTER 0x0D, BITS[1:0] N1 DACCLKP/DACCLKN (PIN 2 AND PIN 3) REGISTER 0x0A, BIT 7 PLL ENABLE
/N0 REGISTER 0x0D, BITS[3:2] N0 DACCLK REGISTER 0x0D, BITS[7:6] /N2 N2
09016-034
PLL LOGIC CONTROL CLOCK
Figure 64. PLL Clock Multiplication Circuit
Rev. 0 | Page 40 of 56
AD9125
PLL Settings
There are three settings for the PLL circuitry that should be programmed to their nominal values. Table 24 lists the recommended PLL settings for these parameters.
Table 24. PLL Settings
PLL SPI Control PLL Loop Bandwidth[2:0] PLL Charge Pump Current[4:0] PLL Cross Control Enable Address Register 0x0C 0x0C 0x0D Bits [7:5] [4:0] 4 Optimal Setting 110 10001 1
Manual VCO Band Select
The device also has a manual band select mode (PLL manual enable, Register 0x0A, Bit 6 = 1) that allows the user to select the VCO tuning band. When in manual mode, the VCO band is set directly with the value written to the manual VCO band, (Register 0x0A, Bits[5:0]). To properly select the VCO band, follow these steps: 1. 2. 3. Put the device in manual band select mode. Sweep the VCO band over a range of bands that result in the PLL being locked. For each band, verify that the PLL is locked and read the PLL using the VCO control voltage (Register 0x0E, Bits[3:0]). Select the band that results in the control voltage being closest to the center of the range, that is, 0000 or 1000 (see Table 25 for more details). The resulting VCO band should be the optimal setting for the device. Write this band to the manual VCO band (Register 0x0A, Bits[5:0]) value. If desired, an indication of where the VCO is within the operating frequency band can be determined by querying the VCO control voltage. Table 25 shows how to interpret the PLL VCO control voltage (Register 0x0E, Bits[3:0]) value.
Configuring the VCO Tuning Band
The PLL VCO has a valid operating range from approximately 1.0 GHz to 2.1 GHz, covered in 63 overlapping frequency bands. For any desired VCO output frequency, there may be several valid PLL band select values. The frequency bands of a typical device are shown in Figure 65. Device-to-device variations and operating temperature affect the actual band frequency range. Therefore, it is required that the optimal PLL band select value be determined for each individual device. 4.
5.
Automatic VCO Band Select
The device has an automatic VCO band select feature on chip. Using the automatic VCO band select feature is a simple and reliable method of configuring the VCO frequency band. This feature is enabled by writing 0x80 to Register 0x0A. When this value is written, the device executes an automated routine that determines the optimal VCO band setting for the device. The setting selected by the device ensures that the PLL remains locked over the full -40C to +85C operating temperature range of the device without further adjustment. (The PLL remains locked over the full temperature range even if the temperature during initialization is at one of the temperature extremes.)
0 4 8 12 16 20
PLL BAND
Table 25. VCO Control Voltage Range Indications
VCO Control Voltage 1111 1110 1101 1100 1011 1010 1001 1000 0111 0110 0101 0100 0011 0010 0001 0000 Indication Move to a higher VCO band VCO is operating in the higher end of the frequency band
VCO is operating within an optimal region of the frequency band
VCO is operating in the lower end of the frequency band
24 28 32 36 40 44 48 52 56 60 1000 1200 1400 1600 1800 2000 2200
09016-035
Move to a lower VCO band
VCO FREQUENCY (MHz)
Figure 65. PLL Lock Range over Temperature for a Typical Device
Rev. 0 | Page 41 of 56
AD9125 ANALOG OUTPUTS
TRANSMIT DAC OPERATION
Figure 66 shows a simplified block diagram of the transmit path DACs. The DAC core consists of a current source array, a switch core, a digital control logic, and a full-scale output current control. The DAC full-scale output current (IOUTFS) is nominally 20 mA. The output currents from the IOUT1P/IOUT2P and IOUT1N/ IOUT2N pins are complementary, meaning that the sum of the two currents always equals the full-scale current of the DAC. The digital input code to the DAC determines the effective differential current delivered to the load.
1.2V 5k REFIO 0.1F FSADJ 10k Q DAC FS ADJUST REGISTER 0x44 CURRENT SCALING IOUT2N Q DAC
09016-037
For nominal values of VREF (1.2 V), RSET (10 k), and DAC gain (512), the full-scale current of the DAC is typically 20.16 mA. The DAC full-scale current can be adjusted from 8.66 mA to 31.66 mA by setting the DAC gain code, as shown in Figure 67.
35
30
25 20
IFS (mA)
I DAC FS ADJUST REGISTER 0x40 I DAC
15
IOUT1P IOUT1N
10 5 0 0 200 400 600 800 1000 DAC GAIN CODE
IOUT2P
Figure 67. DAC Full-Scale Current vs. DAC Gain Code
Figure 66. Simplified Block Diagram of DAC Core
The DAC has a 1.2 V band gap reference with an output impedance of 5 k. The reference output voltage appears on the REFIO pin. When using the internal reference, the REFIO pin should be decoupled to AVSS with a 0.1 F capacitor. Only use the internal reference for external circuits that draw dc currents of 2 A or less. For dynamic loads or static loads greater than 2 A, buffer the REFIO pin. If desired, an external reference (between 1.10 V and 1.30 V) can be applied to the REFIO pin. The internal reference can either be overdriven or powered down by setting Register 0x43, Bit 5. A 10 k external resistor, RSET, must be connected from the FSADJ pin to AVSS. This resistor, along with the reference control amplifier, sets up the correct internal bias currents for the DAC. Because the full-scale current is inversely proportional to this resistor, the tolerance of RSET is reflected in the full-scale output amplitude. The full-scale current equation, where the DAC gain is set individually for the I and Q DACs in Register 0x40 and Register 0x44, respectively, follows: I FS = VREF 3 x 72 + x DAC gain R SET 16
Transmit DAC Transfer Function
The output currents from the IOUT1P/IOUT2P and IOUT1N/ IOUT2N pins are complementary, meaning that the sum of the two currents always equals the full-scale current of the DAC. The digital input code to the DAC determines the effective differential current delivered to the load. IOUT1P/IOUT2P provide maximum output current when all bits are high. The output currents vs. DACCODE for the DAC outputs are expressed as DACCODE I OUTP = x I OUTFS 2N
I OUTN = I OUTFS - I OUTP
09016-036
(1) (2)
where DACCODE = 0 to 2N - 1.
Transmit DAC Output Configurations
The optimum noise and distortion performance of the AD9125 is realized when it is configured for differential operation. The common-mode error sources of the DAC outputs are significantly reduced by the common-mode rejection of a transformer or differential amplifier. These common-mode error sources include even-order distortion products and noise. The enhancement in distortion performance becomes more significant as the frequency content of the reconstructed waveform increases and/or its amplitude increases. This is due to the first-order cancellation of various dynamic common-mode distortion mechanisms, digital feedthrough, and noise.
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AD9125
Figure 68 shows the most basic DAC output circuitry. A pair of resistors, RO, is used to convert each of the complementary output currents to a differential voltage output, VOUT. Because the current outputs of the DAC are high impedance, the differential driving point impedance of the DAC outputs, ROUT, is equal to 2 x RO. Figure 69 illustrates the output voltage waveforms.
IOUT1P RO VOUTI RO IOUT1N VIN - VIP +
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10mA 20mA 30mA
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0.6
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VCMD (V)
Figure 70. IMD vs. Common-Mode Output Voltage (fOUT = 61 MHz, RLOAD = 50 differential, IFS = 10 mA, 20 mA, and 30 mA)
-50 -55 -60
IMD (dBc)
RO IOUT2N
VQN -
Figure 68. Basic Transmit DAC Output Circuit
VPEAK
10mA 20mA 30mA
VCM
-65 -70 -75 -80 -85 0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 VCMD (V)
0 VN VP VOUT -VPEAK
The common-mode signal voltage, VCM, is calculated as
VCM I = FS x RO 2
Figure 71. IMD vs. Common-Mode Output Voltage (fOUT = 161 MHz, RLOAD = 50 differential, IFS = 10 mA, 20 mA, and 30 mA)
AUXILIARY DAC OPERATION
The AD9125 has two auxiliary DACs; one is associated with the I path, and the other is associated with the Q path. These auxiliary DACs can be used to compensate for dc offsets in the transmitted signal. Each auxiliary DAC has a single-ended current that can sink or source current into either the P or N output of the associated transmit DAC. The auxiliary DAC structure is shown in Figure 72.
AVDD3
The peak output voltage, VPEAK, is calculated as VPEAK = IFS x RO With this circuit configuration, the single-ended peak voltage is the same as the peak differential output voltage.
Transmit DAC Linear Output Signal Swing
To achieve optimum performance, the DAC outputs have a linear output compliance voltage range that must be adhered to. The linear output signal swing is dependent on the full-scale output current, IOUTFS, and the common-mode level of the output. Figure 70 and Figure 71 show the IMD performance vs. the common-mode output voltage at various full-scale currents and output frequencies.
AUX DAC AUX DAC CURRENT DIRECTION AUX DAC SIGN IOUTP I DAC IOUTN
Figure 72. Auxiliary DAC Structure
The control registers for controlling the I and Q auxiliary DACs are in Register 0x42, Register 0x43, Register 0x46, and Register 0x47.
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Figure 69. Voltage Output Waveforms
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AD9125
Interfacing to Modulators
The AD9125 interfaces to the ADL537x family of modulators with a minimal number of components. An example of the recommended interface circuitry is shown in Figure 73. The baseband inputs of the ADL537x family require a dc bias of 500 mV. The nominal midscale output current on each output of the DAC is 10 mA (1/2 the full-scale current). Therefore, a single 50 resistor to ground from each DAC output results in the desired 500 mV dc common-mode bias for the inputs to the ADL537x. The signal level can be reduced through the addition of the load resistor in parallel with the modulator inputs. The peak-to-peak voltage swing of the transmitted signal is
DRIVING THE ADL5375-15
The ADL5375-15 is the version of the ADL5375 that offers an input baseband bias levels of 1500 mV. Because the ADL5375-15 requires a 1500 mV dc bias, it requires a slightly more complex interface than most other Analog Devices, Inc., modulators. The DAC output must be level-shifted from a 500 mV dc bias to the 1500 mV dc bias. Level-shifting can be achieved with a purely passive network, as shown in Figure 74. In this network, the dc bias of the DAC remains at 500 mV while the input to the ADL5375-15 is 1500 mV. This passive level-shifting network introduces approximately 2 dB of loss in the ac signal.
AD9125
67 IOUT1P RBIP 45.3 RBIN 66 45.3 IOUT1N 59
RLI 100 IBBN
[2 x R B x R L ] VSIGNAL = I FS x [2 x R B + R L ]
AD9125
67 IOUT1P RBIP 50 RBIN 50 IBBP
RSIN 1k RLIP 3480 RLIN 3480
ADL5375-15
21 IBBP 5V 22 IBBN 9 QBBN 5V QBBP
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RSIP 1k RSQN 1k
IOUT2N RBQN 45.3 RBQP 58 45.3 IOUT2P
QBBN
66 IOUT1N 59 IOUT2N
RLQN 3480 RSQP RLQP 1k 3480
10
RBQN 50 RBQP 50 58 IOUT2P
RLQ 100 QBBP
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Figure 74. Passive Level-Shifting Network for Biasing ADL5375-15
REDUCING LO LEAKAGE AND UNWANTED SIDEBANDS
Analog quadrature modulators can introduce unwanted signals at the LO frequency due to dc offset voltages in the I and Q baseband inputs, as well as feedthrough paths from the LO input to the output. The LO feedthrough can be nulled by applying the correct dc offset voltages at the DAC output. This can be done using the auxiliary DACs (Register 0x42, Register 0x43, Register 0x46, and Register 0x47) or by using the digital dc offset adjustments (Register 0x3C through Register 0x3F). The advantage of using the auxiliary DACs is that none of the main DAC dynamic range is used to perform the dc offset adjustment. However, the disadvantage is that the commonmode level of the output signal changes as a function of the auxiliary DAC current. The opposite is true when the digital offset adjustment is used. Good sideband suppression requires both gain and phase matching of the I and Q signals. The I phase adjust (Register 0x38 and Register 0x39), Q phase adjust (Register 0x3A and Register 0x3B), I DAC FS adjust (Register 0x40 and Register 0x41), and Q DAC FS adjust (Register 0x44 and Register 0x45) registers can be used to calibrate I and Q transmit paths to optimize the sideband suppression.
22pF 33nH 56nH 6pF 33nH 22pF 56nH 3pF 140 ADL537x
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Figure 73. Typical Interface Circuitry Between the AD9125 and the ADL537x Family of Modulators
BASEBAND FILTER IMPLEMENTATION
Most applications require a baseband anti-imaging filter between the DAC and the modulator to filter out Nyquist images and broadband DAC noise. The filter can be inserted between the I-V resistors at the DAC output and the signal-level setting resistor across the modulator input. This configuration establishes the input and output impedances for the filter. Figure 75 shows a fifth-order low-pass filter. A common-mode choke is used between the I-V resistors and the remainder of the filter. This removes the common-mode signal produced by the DAC and prevents the common-mode signal from being converted to a differential signal, which can appear as unwanted spurious signals in the output spectrum. Splitting the first filter capacitor into two and grounding the center point creates a common-mode low-pass filter, providing additional commonmode rejection of high frequency signals. A purely differential filter can pass common-mode signals.
50
3pF
AD9125
50
2pF
Figure 75. DAC Modulator Interface with Fifth-Order, Low Pass Filter
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AD9125 DEVICE POWER DISSIPATION
The AD9125 has four supply rails: AVDD33, IOVDD, DVDD18, and CVDD18. The AVDD33 supply powers the DAC core circuitry. The power dissipation of the AVDD33 supply rail is independent of the digital operating mode and sample rate. The current drawn from the AVDD33 supply rail is typically 57 mA (188 mW) when the full-scale current of the I and Q DACs is set to the nominal value of 20 mA. Changing the full-scale current directly impacts the supply current drawn from the AVDD33 rail. For example, if the full-scale current of the I DAC and the Q DAC is changed to 10 mA, the AVDD33 supply current drops by 20 mA to 37 mA. The IOVDD voltage supplies the serial port I/O pins, the RESET pin, and the IRQ pin. The voltage applied to the IOVDD pin can range from 1.8 V to 3.3 V. The current drawn by the IOVDD supply pin is typically 3 mA. The DVDD18 supply powers all of the digital signal processing blocks of the device. The power consumption from this supply is a function of which digital blocks are enabled and the frequency at which the device is operating. The CVDD18 supply powers the clock receiver and clock distribution circuitry. The power consumption from this supply varies directly with the operating frequency of the device. CVDD18 also powers the PLL. The power dissipation of the PLL is typically 80 mA when enabled. Figure 76 through Figure 80 detail the power dissipation of the AD9125 under a variety of operating conditions. All of the graphs are taken with data being supplied to both the I and Q channels. The power consumption of the device does not vary significantly with changes in the coarse modulation mode selected or analog output frequency. Graphs of the total power dissipation are shown along with the power dissipation of the DVDD18 and CVDD18 supplies. Maximum power dissipation can be estimated to be 20% higher than the typical power dissipation.
POWER (mW)
1800 1600 8x 1400 1200
POWER (mW)
4x 1000 800 600 400 200 0 1x 2x
fDATA (MHz)
Figure 76. Total Power Dissipation vs. fDATA Without PLL, Fine NCO, and Inverse Sinc
1400 1200 8x 1000 4x
POWER (mW)
800 600 2x 400 200 0
1x
fDATA (MHz)
Figure 77. DVDD18 Power Dissipation vs. fDATA Without Fine NCO and Inverse Sinc
250
200
8x 4x
150
100
2x
1x 50
0
fDATA (MHz)
Figure 78. CVDD18 Power Dissipation vs. fDATA with PLL Disabled
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AD9125
300
TEMPERATURE SENSOR
The AD9125 has a diode-based temperature sensor for measuring the temperature of the die. The temperature reading is accessed through Register 0x49 and Register 0x4A. The temperature of the die can be calculated by TDIE = (Die Temp[15:0] - 47,925) 88
250
200
POWER (mW)
150
100
50
where TDIE is the die temperature in oC. The temperature accuracy is 5oC typical. Estimates of the ambient temperature can be made if the power dissipation of the device is known. For example, if the device power dissipation is 800 mW and the measured die temperature is 50oC, then the ambient temperature can be calculated as TA = TDIE - PD x TJA = 50 - 0.8 x 20.7 = 33.4C where: TA is the ambient temperature in oC. TDIE is the die temperature in oC. PD is the power dissipation. TJA is the thermal resistance from junction to ambient of the AD9125, as shown in Table 7. To use the temperature sensor, it must be enabled by setting Register 0x01, Bit 4, to 0. In addition, to obtain accurate readings, the range control register (Register 0x48) should be set to 0x02.
0
fDAC (MHz)
Figure 79. DVDD18 Power Dissipation vs. fDAC Due to Inverse Sinc Filter
300
250
200
POWER (mW)
2x, 4x, 8x 150
100 1x 50
fDATA (MHz)
Figure 80. DVDD18 Power Dissipation vs. fDATA Due to Fine NCO
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AD9125 MULTICHIP SYNCHRONIZATION
System demands may require that the outputs of multiple DACs be synchronized with each other or with a system clock. Systems that support transmit diversity or beam forming, where multiple antennas are used to transmit a correlated signal, require multiple DAC outputs to be phase aligned with each other. Systems with a time division multiplexing transmit chain may require one or more DACs to be synchronized with a system-level reference clock. Multiple devices are considered synchronized to each other when the state of the clock generation state machine is identical for all parts and when time aligned data is being read from the FIFOs of all parts simultaneously. Devices are considered synchronized to a system clock when there is a constant, known relationship among the clock generation state machine, the data being read from the FIFO, and a particular clock edge of the system clock. The AD9125 has provisions for enabling multiple devices to be synchronized to each other or to a system clock. The AD9125 supports synchronization in two modes: data rate mode and FIFO rate mode. Each of these modes has a different lowest rate clock that the synchronization logic attempts to synchronize to. In data rate mode, the input data rate represents the lowest synchronized clock. In FIFO rate mode, the FIFO rate, which is the data rate divided by the FIFO depth of 8, represents the lowest rate clock. The advantage of FIFO rate synchronization is increased time between keep-out windows for DCI changes relative to the DACCLK or REFCLK input. When in data rate mode, the elasticity of the FIFO is not used to absorb timing variations between the data source and the DAC, resulting in keep-out widows repeating at the input data rate. The method chosen for providing the DAC sampling clock directly impacts the synchronization methods available. When the device clock multiplier is used, only data rate mode is available. When the DAC sampling clock is sourced directly, both data rate mode and FIFO rate mode synchronization are available. This section details the synchronization methods for enabling both clocking modes and for querying the status of the synchronization logic. 3.
MATCHED LENGTH TRACES REFCLKP/ REFCLKN FRAME DCI SYSTEM CLOCK LOW SKEW CLOCK DRIVER REFCLKP/ REFCLKN FPGA FRAME DCI IOUT2P/ IOUT2N
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IOUT1P/ IOUT1N
Figure 81. Typical Circuit Diagram for Synchronizing Devices
The Procedure for Synchronization when Using the PLL section outlines the steps required to synchronize multiple devices. The procedure assumes that the REFCLK signal is applied to all devices and that the PLL of each device is phase locked to this signal. This procedure must be carried out on each individual device.
Procedure for Synchronization when Using the PLL
To synchronize all devices, 1. Configure the device for data rate mode and periodic synchronization by writing 0xC0 to the Sync Control 1 register (Register 0x10). Additional synchronization options are available. Read the Sync Status 1 register (Register 0x12) and verify that the sync locked bit (Bit 6) is set high, indicating that the device achieved back-end synchronization and that the sync lost bit (Bit 7) is low. These levels indicate that the clocks are running with a constant, known phase relative to the sync signal. Reset the FIFO by strobing the FRAME signal high for the time required to write two complete input data-words. Resetting the FIFO ensures that the correct data is being read from the FIFO.
2.
SYNCHRONIZATION WITH CLOCK MULTIPLICATION
When using the clock multiplier to generate the DAC sample rate clock, the REFCLK input signal acts both as the reference clock for the PLL-based clock multiplier and as the synchronization signal. To synchronize devices, distribute the REFCLK signal with low skew to all of the devices that need to be synchronized. Skew between the REFCLK signals of the devices shows up directly as a timing mismatch at the DAC outputs. The frequency of the REFCLK signal is typically equal to the input data rate. The FRAME and DCI signals, along with the data, can be created in the FPGA. A circuit diagram of a typical configuration is shown in Figure 81.
To maintain synchronization, the skew between the REFCLK signals of the devices must be less than tSKEW. There are also setup and hold times to be observed among the DCI, the data of each device, and the REFCLK signal. When resetting the FIFO, the FRAME signal must be held high for the time interval required to write two complete input data-words. A timing diagram of the input signals is shown in Figure 82. This example shows a REFCLK frequency equal to the data rate. Although this is the most common situation, it is not strictly required for proper synchronization. Any REFCLK frequency that satisfies the following equation is acceptable: fSYNC_I = fDACCLK/2N and fSYNC_I fDATA where N = 0, 1, 2, or 3. As an example, a configuration with 4x interpolation and clock frequencies of fVCO = 1600 MHz, fDACCLK = 800 MHz, fDATA = 200 MHz, and fSYNC_I = 100 MHz is a viable solution.
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AD9125
tSKEW
REFCLKP(1)/ REFCLKN(1)
REFCLKP(2)/ REFCLKN(2)
tSU_DCI
DCI(2)
tH_DCI
FRAME(2)
Figure 82. Timing Diagram Required for Synchronizing Devices
DACCLKP/ DACCLKN REFCLKP/ REFCLKN FRAME SAMPLE RATE CLOCK DCI LOW SKEW CLOCK DRIVER MATCHED LENGTH TRACES
IOUT1P/ IOUT1N
DACCLKP/ DACCLKN REFCLKP/ REFCLKN SYNC CLOCK LOW SKEW CLOCK DRIVER FRAME DCI
IOUT2P/ IOUT2N
Figure 83. Typical Circuit Diagram for Synchronizing Devices to a System Clock
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FPGA
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AD9125
SYNCHRONIZATION WITH DIRECT CLOCKING
When directly sourcing the DAC sample rate clock, a separate REFCLK input signal is required for synchronization. To synchronize devices, the DACCLK signal and the REFCLK signal must be distributed with low skew to all of the devices being synchronized. If the devices need to be synchronized to a master clock, then use the master clock directly for generating the REFCLK input (see Figure 83). To ensure that each DAC is updated with the correct data on the same CLK edge, two timing relationships must be met on each DAC. DCI and D[31:0] must meet the setup and hold times with respect to the rising edge of DACCLK, and REFCLK must meet the setup and hold times with respect to the rising edge of DACCLK. When resetting the FIFO, the FRAME signal must be held high for the time required to input two complete input data-words. When these conditions are met, the outputs of the DACs are updated within tSKEW + tOUTDLY of each other. A timing diagram that illustrates the timing requirements of the input signals is shown in Figure 84. Figure 84 shows the synchronization signal timing with 2x interpolation; therefore, fDCI = 1/2 x fCLK. The REFCLK input is shown to be equal to the data rate. The maximum frequency at which the device can be resynchronized in data rate mode can be expressed as fSYNC_I = fDATA/2N where N is any nonnegative integer. Generally, for values of N equal to or greater than 3, select the FIFO rate synchronization mode.
Table 26. DCI-DAC Setup and Hold Times
Minimum Setup Time, tSU_DCI (ns) 0.16 Minimum Hold Time, tH_DCI (ns) 0.59
DATA RATE MODE SYNCHRONIZATION
The Procedure for Data Rate Synchronization when Directly Sourcing the DAC Sampling Clock section outlines the steps required to synchronize multiple devices in data rate mode. The procedure assumes that the DACCLK and REFCLK signals are applied to all of the devices. The procedure must be carried out on each individual device.
Procedure for Data Rate Synchronization When Directly Sourcing the DAC Sampling Clock
To synchronize all devices, 1. Configure the device for data rate mode and periodic synchronization by writing 0xC0 to the Sync Control 1 register (Register 0x10). Additional synchronization options are available and are described in the Additional Synchronization Features section. Poll the sync locked bit (Register 0x12, Bit 6) to verify that the device is back-end synchronized. A high level on this bit indicates that the clocks are running with a constant, known phase relative to the sync signal. Reset the FIFO by strobing the FRAME signal high for the time required to write two complete input data-words. Resetting the FIFO ensures that the correct data is being read from the FIFO of each of the devices simultaneously.
2.
3.
tSKEW
DACCLKP(1)/ DACCLKN(1)
DACCLKP(2)/ DACCLKN(2)
tSU_SYNC tH_SYNC
REFCLKP(2)/ REFCLKN(2)
tSU_DCI tH_DCI
DCI2(2)
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FRAME(2)
Figure 84. Data Rate Synchronization Signal Timing Requirements, 2x Interpolation
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AD9125
FIFO RATE MODE SYNCHRONIZATION
The Procedure for FIFO Rate Synchronization when Directly Sourcing the DAC Sampling Clock section outlines the steps required to synchronize multiple devices in FIFO rate mode. The procedure assumes that the REFCLK and DACCLK signals are applied to all of the devices. The procedure must be carried out on each individual device. To ensure that each DAC is updated with the correct data on the same CLK edge, two timing relationships must be met on each DAC. DCI and D[31:0] must meet the setup and hold times with respect to the rising edge of DACCLK, and REFCLK must meet the setup and hold times with respect to the rising edge of DACCLK. When resetting the FIFO, the FRAME signal must be held high for at least three data periods (that is, 1.5 cycles of DCI). When these conditions are met, the outputs of the DACs are updated within tSKEW + tOUTDLY of each other. A timing diagram that illustrates the timing requirements of the input signals is shown in Figure 85. Figure 85 shows the synchronization signal timing with 2x interpolation; therefore, fDCI = 1/2 x fCLK. The REFCLK input is shown to be equal to the FIFO rate. More generally, the maximum frequency at which the device can be resynchronized in FIFO rate mode can be expressed as fSYNC_I = fDATA/(8 x 2N) where N is any nonnegative integer.
Procedure for FIFO Rate Synchronization When Directly Sourcing the DAC Sampling Clock
To synchronize all devices, 1. Configure the device for FIFO rate mode and periodic synchronization by writing 0x80 to the Sync Control 1 register (Register 0x10). Additional synchronization options are available and are described in the Additional Synchronization Features section. Poll the sync locked bit (Register 0x12, Bit 6) to verify that the device is back-end synchronized. A high level on this bit indicates that the clocks are running with a constant and known phase relative to the sync signal. Reset the FIFO by strobing the FRAME signal high for the time required to write two complete input data-words. Resetting the FIFO ensures that the correct data is being read from the FIFO of each of the devices simultaneously.
2.
3.
tSKEW
DACCLKP(1)/ DACCLKN(1)
DACCLKP(2)/ DACCLKN(2)
tSU_SYNC tH_SYNC
REFCLKP(2)/ REFCLKN(2)
DCI2
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FRAME2
Figure 85. FIFO Rate Synchronization Signal Timing Requirements, 2x Interpolation
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AD9125
ADDITIONAL SYNCHRONIZATION FEATURES
The synchronization logic incorporates additional features that provide means for querying the status of the synchronization, improving the robustness of the synchronization, and enabling a one-shot synchronization mode. These features are detailed in the Sync Status Bits and Timing Optimization sections. The synchronization logic resynchronizes when a phase change between the REFCLK signal and the state of the clock generation state machine exceeds a threshold. To mitigate the effects of jitter and prevent erroneous resynchronizations, the relative phase can be averaged. The amount of averaging is set by the sync averaging bits (Register 0x10, Bits[2:0]) and can be set from 1 to 128. The higher the number of averages, the more slowly the device recognizes and resynchronizes to a legitimate phase correction. Generally, the averaging should be made as large as possible while still meeting the allotted resynchronization time interval. The value of the sync phase request bits (Register 0x11, Bits[5:0]) is the state to which the clock generation state machine resets upon initialization. By varying this value, the timing of the internal clocks with respect to the REFCLK signal can be adjusted. Every increment in the value of the sync phase request bits (Register 0x11, Bits[5:0]) advances the internal clocks by one DACCLK period. This offset can be used for two purposes: to skew the outputs of two synchronized DAC outputs in increments of the DACCLK period and to change the relative timing between the DCI input and REFCLK. This may allow for more optimal placement of the DCI sampling point in data rate synchronization mode.
Table 27. Synchronization Setup and Hold Times
Parameter tSKEW tSV_SYNC TH_SYNC Min -tDACCLK/2 100 330 Max +tDACCLK/2 Unit ps ps ps
Sync Status Bits
When the sync locked bit (Register 0x12, Bit 6) is set, it indicates that the synchronization logic has reached alignment. This alignment is determined when the clock generation state machine phase is constant. It takes between (11 + averaging) x 64 and (11 + averaging) x 128 DACCLK cycles. This bit can optionally trigger an IRQ, as described in the Interrupt Request Operation section. When the sync lost bit (Register 0x12, Bit 7) is set, it indicates a previously synchronized device has lost alignment. This bit is latched and remains set until cleared by overwriting the register. This bit can optionally trigger an IRQ, as described in the Interrupt Request Operation section. The sync phase readback bits (Register 0x13, Bits[7:0]) report the current clock phase in a 6.2 format. Bits[7:2] report which of the 64 states (0 to 63) the clock is currently in. When averaging is enabled, Bits[1:0] provide 1/4 state accuracy (for 0, 1/4, 1/2, 3/4). The lower two bits give an indication of the timing margin issues that may exist. If the sync sampling is error free, the fractional clock state should be 00.
Timing Optimization
The REFCLK signal is sampled by a version of the DACCLK. If sampling errors are being detected, the opposite sampling edge can be selected to improve the sampling point. The sampling edge can be selected by setting Register 0x10, Bit 3 (1 = rising and 0 = falling).
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AD9125 INTERRUPT REQUEST OPERATION
The AD9125 provides an interrupt request output signal (on Pin 7, IRQ) that can be used to notify an external host processor of significant device events. Upon assertion of the interrupt, the device should be queried to determine the precise event that occurred. The IRQ pin is an open-drain, active low output. Pull the IRQ pin high external to the device. This pin can be tied to the interrupt pins of other devices with open-drain outputs to wire-OR these pins together. Sixteen event flags provide visibility into the device. These 16 flags are located in the two event flag registers (Register 0x06 and Register 0x07). The behavior of each of the event flags is independently selected in the interrupt enable registers (Register 0x04 and Register 0x05). When the flag interrupt enable is active, the event flag latches and triggers an external interrupt. When the flag interrupt is disabled, the event flag simply monitors the source signal and the external IRQ remains inactive. Figure 86 shows the IRQ-related circuitry. This diagram shows how event flag signals propagate to the IRQ output. The INTERRUPT_ ENABLE signal represents one bit from the interrupt enable registers. The EVENT_FLAG_SOURCE signal represents one bit from the event flag registers. The EVENT_FLAG_SOURCE signal represents one of the device signals that can be monitored, such as the PLL_LOCKED signal from the PLL phase detector or the FIFO_WARNING_1 signal from the FIFO controller. When an interrupt enable bit is set high, the corresponding event flag bit reflects a positively tripped signal (that is, latched on the rising edge of the EVENT_FLAG_SOURCE signal). This signal also asserts the external IRQ. When an interrupt enable bit is set low, the event flag bit reflects the current status of the EVENT_ FLAG_SOURCE signal, but the event flag has no effect on the external IRQ. The latched version of an event flag (the INTERRUPT_SOURCE signal) can be cleared in two ways. The recommended way is by writing 1 to the corresponding event flag bit; however, a hardware or software reset can also clear the INTERRUPT_SOURCE.
INTERRUPT SERVICE ROUTINE
The interrupt request management starts by selecting the set of event flags that require host intervention or monitoring. Those events that require host action should be enabled so that the host is notified when they occur. For events requiring host intervention, upon IRQ activation, run the following routine to clear an interrupt request: 1. 2. 3. Read the status of the event flag bits that are being monitored. Set the interrupt enable bit low so that the unlatched EVENT_ FLAG_SOURCE signal can be monitored directly. Perform any actions that are required to clear the EVENT_ SOURCE_FLAG signal. In many cases, no specific actions are required. Read the event flag to verify that the EVENT_FLAG_ SOURCE signal has been cleared. Clear the interrupt by writing 1 to the event flag bit. Set the interrupt enable bits of the events to be monitored.
4. 5. 6.
Note that some of the EVENT_FLAG_SOURCE signals are latched signals. These are cleared by writing to the corresponding event flag bit. Details of each of the event flags can be found in Table 11.
0 1
EVENT_FLAG
IRQ INTERRUPT_ENABLE EVENT_FLAG_SOURCE INTERRUPT SOURCE OTHER INTERRUPT SOURCES
DEVICE_RESET
Figure 86. Simplified Schematic of IRQ Circuitry
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AD9125 INTERFACE TIMING VALIDATION
The AD9125 provides on-chip sample error detection (SED) circuitry that simplifies verification of the input data interface. The SED compares the input data samples captured at the digital input pins with a set of comparison values, which are loaded into registers through the SPI port. Differences between these values are detected and stored. Options are available for customizing SED test sequencing and error handling. changes the behavior of Register 0x70 through Register 0x73. The compare pass bit is set if the last comparison indicated that the sample was error free. The compare fail bit is set if an error is detected. The compare fail bit is automatically cleared by the reception of eight consecutive error-free comparisons. When autoclear mode is enabled, Register 0x70 through Register 0x73 accumulate errors as previously described but reset to all 0s after eight consecutive error-free sample comparisons are made. The sample error, compare pass, and compare fail flags can be configured to trigger an IRQ when active, if desired. This is done by enabling the appropriate bits in the Event Flag 2 register (Register 0x07). Table 28 shows a progression of the input sample comparison results and the corresponding states of the error flags.
SED OPERATION
The SED circuitry operates on a data set made up of four 16-bit input words, denoted as I0, Q0, I1, and Q1. To properly align the input samples, the first I and Q data-words (that is, I0 and Q0) are indicated by asserting the FRAME signal for a minimum of two complete input samples. Figure 87 shows the input timing of the interface in dual-word mode. The FRAME signal can be issued once at the start of the data transmission, or it can be asserted repeatedly at intervals coinciding with the I0 and Q0 data-words.
FRAME
SED EXAMPLE
Normal Operation
The following example illustrates the SED configuration for continuously monitoring the input data and assertion of an IRQ when a single error is detected. 1. Write to the following registers to enable the SED and load the comparison values. Register 0x67: 0x80 Register 0x68: I0[7:0] Register 0x69: I0[15:8] Register 0x6A: Q0[7:0] Register 0x6B: Q0[15:8] Register 0x6C: I1[7:0] Register 0x6D: I1[15:8] Register 0x6E: Q1[7:0] Register 0x6F: Q1[15:8] Comparison values can be chosen arbitrarily; however, choosing values that require frequent bit toggling provides the most robust test. Enable the SED error detect flag to assert the IRQ pin by writing 0x04 to Register 0x05. Begin transmitting the input data pattern.
D[31:16]
I0
I1
I0
I1
I0
09016-055
D[15:0]
Q0
Q1
Q0
Q1
Q0
Figure 87. Timing Diagram for Dual-Word Mode SED Operation
In word mode, the FRAME signal required to align the data samples needs to be extended. The FRAME signal can be issued once at the start of the data transmission, or it can be asserted repeatedly at intervals coinciding with the I0 and Q0 data-words.
FRAME
09016-056
D[15:0]
I0
Q0
I1
Q1
I0
Q0
Figure 88. Timing Diagram for Two-Port Mode SED Operation
The SED has three flag bits (Register 0x67, Bit 0, Bit 1, and Bit 5) that indicate the results of the input sample comparisons. The sample error detected bit (Register 0x67, Bit 5) is set when an error is detected and remains set until the bit is cleared. The SED also provides registers that indicate which input data bits experienced errors (Register 0x70 through Register 0x73). These bits are latched and indicate the accumulated errors detected until cleared. The autoclear mode has two effects: it activates the compare fail bit and the compare pass bit (Register 0x67, Bit 1 and Bit 0) and
2. 3.
If IRQ is asserted, read Register 0x67 and Register 0x70 through Register 0x73 to verify that a SED error was detected and to determine which input bits were in error. The bits in Register 0x70 through Register 0x73 are latched; therefore, the bits indicate any errors that occurred on those bits throughout the test, not just the errors that caused the error detected flag to be set.
Table 28. Progression of Comparison Outcomes and the Resulting SED Register Values
Compare Results (Pass/Fail) Register 0x67, Bit 5 (Sample Error Detected) Register 0x67, Bit 1 (Compare Fail) Register 0x67, Bit 0 (Compare Pass) Register 0x70 to Register 0x73 (Errors Detected x_BITS[15:0])
1 2
P 0 0 1 Z1
F 1 1 0 N2
F 1 1 0 N2
F 1 1 0 N2
P 1 1 1 N2
P 1 1 1 N2
P 1 1 1 N2
P 1 1 1 N2
P 1 1 1 N2
P 1 1 1 N2
P 1 1 1 N2
P 1 1 1 N2
P 1 0 1 Z1
F 1 1 0 N2
P 1 1 1 N2
F 1 1 0 N2
Z = all 0s. N = nonzero. Rev. 0 | Page 53 of 56
AD9125
EXAMPLE START-UP ROUTINE
There are certain sequences that should be followed to ensure reliable startup of the AD9125. The example start-up routine assumes the following device configuration: * * * * * * * * * fDATA = 122.88 MSPS Interpolation = 4x, using HB1 = 10 and HB2 = 010010 Input data = baseband data fOUT = 140 MHz fREFCLK = 122.88 MHz PLL = enabled Fine NCO = enabled Inverse SINC filter = enabled Synchronization = enabled
Start-Up Sequence
The following procedure sets the power clock and register write sequencing for reliable device start-up: 1. 2. 3. 4. Power up the device (no specific power supply sequence is required). Apply stable REFCLK input signal. Apply stable DCI input signal. Issue a hardware reset (optional).
As a result, the device configuration register write sequence is
0x00 0x00 0x0C 0x0D 0x0A 0x0A 0x20 /* Issue software reset */ 0x00 0xD1 /* Start PLL */ 0xD9 0xC0 0x80 /* ??Verify PLL is locked?? */ Read 0x0E, expect Bit 7 = 1, Bit 6 = 0 Read 0x06, expect 0x5C 0x10 0x17 0x18 0x18 0x48 /* Choose data rate mode */ 0x04 /* Issue software FIFO reset */ 0x02 0x00 /* ??Verify FIFO reset?? */ Read 0x18, expect 0x05 Read 0x19, expect 0x07 0x1B 0x84 /* Configure interpolation filters */ 0x1C 0x1D 0x1E 0x30 0x31 0x32 0x33 0x04 0x24 0x01 /* Configure NCO */ 0x55 0x55 0xD5 0x11
The following PLL settings can be derived from the device configuration: * * * * fDACCLK = fDATA x Interpolation = 491.52 MHz fVCO = 4 x fDACCLK = 1966.08 MHz (1 GHz < fVCO < 2.1 GHz) N1 = fDACCLK/fREFCLK = 4 N2 = fVCO/fDACCLK = 4
The following NCO settings can be derived from the device configuration: * * * fNCO = 2 x fDATA fCARRIER = fOUT - fMODHB1 = 140 - 122.88 = 17.12 MHz FTW = 17.12/(2 x 122.88) x 232 = 0x11D55555
0x36 0x01 /* Update frequency tuning word */ 0x36 0x00
Rev. 0 | Page 54 of 56
AD9125 OUTLINE DIMENSIONS
10.00 BSC SQ 0.60 0.42 0.24 0.60 0.42 0.24
55 54 72
1
PIN 1 INDICATOR
PIN 1 INDICATOR 9.75 BSC SQ 0.50 BSC EXPOSED PAD
(BOTTOM VIEW)
TOP VIEW
6.15 6.00 SQ 5.85
0.50 0.40 0.30 1.00 0.85 0.80 SEATING PLANE 12 MAX 0.80 MAX 0.65 TYP 0.05 MAX 0.02 NOM COPLANARITY 0.08 0.20 REF
37 36
18 19
8.50 REF FOR PROPER CONNECTION OF THE EXPOSED PAD, REFER TO THE PIN CONFIGURATION AND FUNCTION DESCRIPTIONS SECTION OF THIS DATA SHEET.
052809-A
0.30 0.23 0.18
COMPLIANT TO JEDEC STANDARDS MO-220-VNND-4
Figure 89. 72-Lead Lead Frame Chip Scale Package [LFCSP_VQ] 10 mm x 10 mm Body, Very Thin Quad (CP-72-7) Dimensions shown in millimeters
ORDERING GUIDE
Model 1 AD9125BCPZ AD9125BCPZRL AD9125-M5372-EBZ AD9125-M5375-EBZ
1
Temperature Range -40C to +85C -40C to +85C
Package Description 72-lead LFCSP_VQ 72-lead LFCSP_VQ Evaluation Board Connected to ADL5372 Modulator Evaluation Board Connected to ADL5375 Modulator
Package Option CP-72-7 CP-72-7
Z = RoHS Compliant Part.
Rev. 0 | Page 55 of 56
AD9125 NOTES
(c)2010 Analog Devices, Inc. All rights reserved. Trademarks and registered trademarks are the property of their respective owners. D09016-0-6/10(0)
Rev. 0 | Page 56 of 56

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