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ISL5827
Data Sheet May 2004 FN6083
Dual 12-bit, +3.3V, 260+MSPS, High Speed D/A Converter
The ISL5827 is a dual 12-bit, 260+MSPS (Mega Samples Per Second), CMOS, high speed, low power, D/A (digital to analog) converter, designed specifically for use in high performance communication systems such as base transceiver stations utilizing 2.5G or 3G cellular protocols. This device complements the ISL5x57 and ISL5x27 families of high speed converters, which include 8-, 10-, 12-, and 14-bit devices.
Features
* Low Power . . . . . 233mW with 20mA Output at 130MSPS * Adjustable Full Scale Output Current . . . . . 2mA to 20mA * Guaranteed Gain Matching < 0.14dB * +3.3V Power Supply * 3V LVCMOS Compatible Inputs * Excellent Spurious Free Dynamic Range (73dBc to Nyquist, f S = 130MSPS, fOUT = 10MHz) * UMTS Adjacent Channel Power = 70dB at 19.2MHz * EDGE/GSM SFDR = 90dBc at 11MHz in 20MHz Window
Ordering Information
PART NUMBER ISL5827IN ISL5827EVAL1 TEMP. RANGE (C) -40 to 85 25 PACKAGE 48 Ld LQFP PKG. DWG. # CLOCK SPEED
* Dual, 3.3V, Lower Power Replacement for AD9765
Q48.7x7A 260MHz 260MHz
Applications
* Cellular Infrastructure - Single or Multi-Carrier: IS-136, IS-95, GSM, EDGE, CDMA2000, WCDMA, TDS-CDMA * BWA Infrastructure
Evaluation Platform
Pinout
ISL5827 (LQFP) TOP VIEW
ID11 (MSB) QD0 (LSB)
* Quadrature Transmit with IF Range 0-80MHz * Medical/Test Instrumentation and Equipment * Wireless Communication Systems
QD1 QD2 QD3
ID9 ID10
ID7
ID6
ID8
ID5 ID4 ID3 ID2 ID1 (LSB) ID0 NC NC SLEEP DVDD AGND ICOMP
1 2 3 4 5 6 7 8 9 10 11 12
48 47 46 45 44 43 42 41 40 39 38 37 36 35 34 33 32 31 30 29 28 27 26 25 13 14 15 16 17 18 19 20 21 22 23 24
NC NC
QD4 QD5 QD6 QD7 QD8 QD9 QD10 QD11 (MSB) CLK DGND AGND QCOMP
REFLO
AGND FSADJ
IOUTA IOUTB
QOUTB QOUTA
REFIO
AVDD
1
AVDD
NC
NC
CAUTION: These devices are sensitive to electrostatic discharge; follow proper IC Handling Procedures. 1-888-INTERSIL or 321-724-7143 | Intersil (and design) is a registered trademark of Intersil Americas Inc. Copyright (c) Intersil Americas Inc. 2004. All Rights Reserved All other trademarks mentioned are the property of their respective owners.
ISL5827 Typical Applications Circuit
ID6 ID7 ID8 ID9 ID10 ID11 (MSB) NC NC QD0 (LSB) QD1 QD2 QD3 48 47 46 45 44 43 42 41 40 39 38 37 36 1 35 2 34 3 33 4 32 5 31 6 30 7 29 8 CLK 28 9 DGND 27 10 DVDD AGND 26 11 AGND 25 12 13 14 15 16 17 18 19 20 21 22 23 24 REFIO REFLO AGND FSADJ AVDD C4 0.1F AVDD C5 0.1F
ID5 ID4 ID3 ID2 ID1 (LSB) ID0 NC NC DVPP C1 0.1F
SLEEP
QD4 QD5 QD6 QD7 QD8 QD9 QD10 QD11 (MSB) R1 50 C3 0.1F AVPP
ICOMP
QCOMP
C2 0.1F AVPP
C6 0.1F RSET 1.91k 50 R2 R3
50
1:1 TRANSFORMER REPRESENTS ANY 50 LOAD (50) IOUT BEAD FERRITE + C11 10F +3.3V POWER SOURCE FERRITE BEAD + C14 10F L2 10H AVPP (ANALOG POWER PLANE) = +3.3V C12 0.1F C13 1F L1 10H DVPP (DIGITAL POWER PLANE) = +3.3V C9 0.1F C10 1F (50) QOUT
2
ISL5827 Functional Block Diagram
NC NC (LSB) QD0 QD1 QD2 QD3 QD4 QD5 QD6 QD7 QD8 QD9 QD10 (MSB) QD11 UPPER 5-BIT DECODER 7 LSBs INPUT LATCH CASCODE 38 SWITCH MATRIX 38 CURRENT SOURCE
QOUTA QOUTB
+ 31 MSB SEGMENTS
QCOMP SLEEP CLK INT/EXT VOLTAGE REFERENCE BIAS GENERATION FSADJ REFIO REFLO ICOMP
NC NC (LSB) ID0 ID1 ID2 ID3 ID4 ID5 ID6 ID7 ID8 ID9 ID10 (MSB) ID11 UPPER 5-BIT DECODER + 31 MSB SEGMENTS 7 LSBs INPUT LATCH CASCODE 38 SWITCH MATRIX 38 CURRENT SOURCE IOUTA IOUTB
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ISL5827 Pin Descriptions
PIN NO. 11, 19, 26 13, 24 28 27 10 20 14, 23 12, 25 1-6, 29-40, 43-48 15, 22 16, 21 17 18 7, 8, 41, 42 9 PIN NAME AGND AVDD CLK DGND DVDD FSADJ NC ICOMP, QCOMP Analog ground. Analog supply (+2.7V to +3.6V). Clock input. Connect to digital ground. Digital supply (+2.7V to +3.6V). Full scale current adjust. Use a resistor to ground to adjust full scale output current. Full scale output current = 32 x VFSADJ/RSET. Not internally connected. Recommend no connect. Compensation pin for internal bias generation. Each pin should be individually decoupled to AGND with a 0.1F capacitor. PIN DESCRIPTION
ID11-ID0, QD11-QD0 Digital data input ports. Bit 11 is most significant bit (MSB) and bit 0 is the least significant bit (LSB). IOUTA, QOUTA IOUTB, QOUTB REFIO REFLO NC SLEEP Current outputs of the device. Full scale output current is achieved when all input bits are set to binary 1. Complementary current outputs of the device. Full scale output current is achieved on the complementary outputs when all input bits are set to binary 0. Reference voltage input if Internal reference is disabled. The internal reference is not intended to drive an external load. Use 0.1F cap to ground when internal reference is enabled. Connect to analog ground to enable internal 1.2V reference or connect to AVDD to disable internal reference. No connect (NC). Not internally connected. No termination required, may be used for device migration to higher resolution DACs. Connect to digital ground or leave floating for normal operation. Connect to DVDD for sleep mode.
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ISL5827
Absolute Maximum Ratings
Digital Supply Voltage DVDD to DGND . . . . . . . . . . . . . . . . . . +3.6V Analog Supply Voltage AVDD to AGND . . . . . . . . . . . . . . . . . . +3.6V Grounds, AGND TO DGND . . . . . . . . . . . . . . . . . . . . -0.3V to +0.3V Digital Input Voltages (DATA, CLK, SLEEP) . . . . . . . . DVDD + 0.3V Reference Input Voltage Range. . . . . . . . . . . . . . . . . . AVDD + 0.3V Analog Output Current (IOUT) . . . . . . . . . . . . . . . . . . . . . . . . . 24mA
Thermal Information
Thermal Resistance (Typical, Note 1) JA(C/W) LQFP Package. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70 Maximum Junction Temperature . . . . . . . . . . . . . . . . . . . . . . . 150C Maximum Storage Temperature Range . . . . . . . . . . . -65C to 150C Maximum Lead Temperature (Soldering 10s) . . . . . . . . . . . . . 300C
Operating Conditions
Temperature Range . . . . . . . . . . . . . . . . . . . . . . . . . . .-40C to 85C
CAUTION: Stresses above those listed in "Absolute Maximum Ratings" may cause permanent damage to the device. This is a stress only rating and operation of the device at these or any other conditions above those indicated in the operational sections of this specification is not implied.
NOTE: 1. JA is measured with the component mounted on an evaluation PC board in free air.
Electrical Specifications
PARAMETER SYSTEM PERFORMANCE Resolution Integral Linearity Error, INL Differential Linearity Error, DNL Offset Error, IOS Offset Drift Coefficient Full Scale Gain Error, FSE
AVDD = DVDD = +3.3V, VREF = Internal 1.2V, IOUTFS = 20mA, TA = 25C for All Typical Values TA = -40C TO 85C TEST CONDITIONS MIN TYP MAX UNITS
12 "Best Fit" Straight Line (Note 8) (Note 8) IOUTA (Note 8) (Note 8) With External Reference (Notes 2, 8) With Internal Reference (Notes 2, 8) -1.25 -1 -0.006 -3 -3 -1.6 -0.14 2 (Note 3) -1.0
0.5 0.5
+1.25 +1 +0.006
Bits LSB LSB % FSR ppm FSR/C % FSR % FSR ppm FSR/C ppm FSR/C dB dB dB % FSR dB FSR mA V
0.1 0.5 0.5 50 100 83 74 73 0.6 0.05 20 -
+3 +3 +1.6 +0.14 22 1.25
Full Scale Gain Drift
With External Reference (Note 8) With Internal Reference (Note 8)
Crosstalk
fCLK = 100MSPS, fOUT = 10MHz fCLK = 100MSPS, fOUT = 40MHz fCLK = 260MSPS, fOUT = 40.4MHz
Gain Matching Between Channels (DC Measurement) Full Scale Output Current, IFS Output Voltage Compliance Range DYNAMIC CHARACTERISTICS Maximum Clock Rate, fCLK Output Rise Time Output Fall Time Output Capacitance Output Noise
As a percentage of Full Scale Range In dB Full Scale Range
260 Full Scale Step Full Scale Step IOUTFS = 20mA IOUTFS = 2mA -
300 1 1 5 50 30
-
MHz ns ns pF pA/Hz pA/Hz
5
ISL5827
Electrical Specifications
PARAMETER AVDD = DVDD = +3.3V, VREF = Internal 1.2V, IOUTFS = 20mA, TA = 25C for All Typical Values (Continued) TA = -40C TO 85C TEST CONDITIONS MIN TYP MAX UNITS
AC CHARACTERISTICS (Using Figure 13 with RDIFF = 50 and RLOAD = 50, Full Scale Output = -2.5dBm) Spurious Free Dynamic Range, SFDR Within a Window fCLK = 210MSPS, fOUT = 80.8MHz, 30MHz Span (Notes 4, 8) fCLK = 210MSPS, fOUT = 40.4MHz, 30MHz Span (Notes 4, 8) fCLK = 130MSPS, fOUT = 20.2MHz, 20MHz Span (Notes 4, 8) Spurious Free Dynamic Range, SFDR to Nyquist (fCLK/2) fCLK = 260MSPS, fOUT = 80.8MHz (Notes 4, 8) fCLK = 260MSPS, fOUT = 40.4MHz (Notes 4, 8) fCLK = 260MSPS, fOUT = 20.2MHz (Notes 4, 8) fCLK = 210MSPS, fOUT = 80.8MHz (Notes 4, 8) fCLK = 210MSPS, fOUT = 40.4MHz (Notes 4, 8, 10) fCLK = 200MSPS, fOUT = 20.2MHz, T = 25C (Notes 4, 8) fCLK = 200MSPS, fOUT = 20.2MHz, T = -40C to 85C (Notes 4, 8) fCLK = 130MSPS, fOUT = 50.5MHz (Notes 4, 8) fCLK = 130MSPS, fOUT = 40.4MHz (Notes 4, 8) fCLK = 130MSPS, fOUT = 20.2MHz (Notes 4, 8) fCLK = 130MSPS, fOUT = 10.1MHz, T = -40C to 85C (Notes 4, 8) fCLK = 130MSPS, fOUT = 5.05MHz (Notes 4, 8) fCLK = 100MSPS, fOUT = 40.4MHz (Notes 4, 8) fCLK = 80MSPS, fOUT = 30.3MHz (Notes 4, 8) fCLK = 80MSPS, fOUT = 20.2MHz (Notes 4, 8) fCLK = 80MSPS, fOUT = 10.1MHz (Notes 4, 8, 10) fCLK = 80MSPS, fOUT = 5.05MHz (Notes 4, 8) fCLK = 50MSPS, fOUT = 20.2MHz (Notes 4, 8) fCLK = 50MSPS, fOUT = 10.1MHz (Notes 4, 8) fCLK = 50MSPS, fOUT = 5.05MHz (Notes 4, 8) Spurious Free Dynamic Range, SFDR in a Window with Eight Tones fCLK = 210MSPS, fOUT = 28.3MHz to 45.2MHz, 2.1MHz Spacing, 50MHz Span (Notes 4, 8, 10) fCLK = 130MSPS, fOUT = 17.5MHz to 27.9MHz, 1.3MHz Spacing, 35MHz Span (Notes 4, 8) fCLK = 80MSPS, fOUT = 10.8MHz to 17.2MHz, 811kHz Spacing, 15MHz Span (Notes 4, 8) fCLK = 50MSPS, fOUT = 6.7MHz to 10.8MHz, 490kHz Spacing, 10MHz Span (Notes 4, 8) Spurious Free Dynamic Range, fCLK = 78MSPS, fOUT = 11MHz, in a 20MHz Window, RBW = 30kHz SFDR in a Window with EDGE or GSM (Notes 4, 8, 10) Adjacent Channel Power Ratio, ACPR with UMTS VOLTAGE REFERENCE Internal Reference Voltage, VFSADJ Internal Reference Voltage Drift Internal Reference Output Current Sink/Source Capability Reference is not intended to drive an external load Pin 20 Voltage with Internal Reference 1.2 1.23 40 0 1.3 V ppm/C A fCLK = 76.8MSPS, fOUT = 19.2MHz, RBW = 30kHz (Notes 4, 8, 10) 60 58 68 72 78 84 54 63 66 54 65 66 57 62 69 73 77 60 63 70 73 76 66 73 77 64 67 74 75 90 70 dBc dBc dBc dBc dBc dBc dBc dBc dBc dBc dBc dBc dBc dBc dBc dBc dBc dBc dBc dBc dBc dBc dBc dBc dBc dBc dBc dBc dB
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ISL5827
Electrical Specifications
PARAMETER Reference Input Impedance Reference Input Multiplying Bandwidth (Note 8) DIGITAL INPUTS D11-D0, CLK (Note 3) (Note 3) 2.3 -25 -20 -10 3.3 0 3 1.0 +25 +20 +10 V V A A A pF AVDD = DVDD = +3.3V, VREF = Internal 1.2V, IOUTFS = 20mA, TA = 25C for All Typical Values (Continued) TA = -40C TO 85C TEST CONDITIONS MIN TYP 1 1.0 MAX UNITS M MHz
Input Logic High Voltage with 3.3V Supply, VIH Input Logic Low Voltage with 3.3V Supply, VIL Sleep Input Current, IIH Input Logic Current, IIH, IL Clock Input Current, IIH, IL Digital Input Capacitance, CIN TIMING CHARACTERISTICS Data Setup Time, tSU Data Hold Time, tHLD Propagation Delay Time, tPD CLK Pulse Width, tPW1 , tPW2
See Figure 15 See Figure 15 See Figure 15 See Figure 15 (Note 3)
2
1.5 1.5 1 -
-
ns ns Clock Period ns
POWER SUPPLY CHARACTERISTICS AVDD Power Supply DVDD Power Supply Analog Supply Current (IAVDD) (Note 9) (Note 9) 3.3V, IOUTFS = 20mA 3.3V, IOUTFS = 2mA Digital Supply Current (IDVDD) 3.3V (Note 5) 3.3V (Note 6) Supply Current (IAVDD) Sleep Mode Power Dissipation 3.3V, IOUTFS = Don't Care 3.3V, IOUTFS = 20mA (Note 5) 3.3V, IOUTFS = 20mA (Note 6) 3.3V, IOUTFS = 20mA (Note 7) 3.3V, IOUTFS = 2mA (Note 5) Power Supply Rejection NOTES: 2. Gain Error measured as the error in the ratio between the full scale output current and the current through RSET (typically 625A). Ideally the ratio should be 32. 3. Parameter guaranteed by design or characterization and not production tested. 4. Spectral measurements made with differential transformer coupled output and no external filtering. For multitone testing, the same pattern was used at different clock rates, producing different output frequencies but at the same ratio to the clock rate. 5. Measured with the clock at 130MSPS and the output frequency at 10MHz. 6. Measured with the clock at 200MSPS and the output frequency at 20MHz. 7. Measured with the clock at 260MSPS and the output frequency at 40.4MHz. 8. See Definition of Specifications. 9. Recommended operation is from 3.0V to 3.6V. Operation below 3.0V is possible with some degradation in spectral performance. Reduction in analog output current may be necessary to maintain spectral performance. 10. See Typical Performance plots. Single Supply (Note 8) 2.7 2.7 -0.125 3.3 3.3 60 24 11 17 5 233 253 275 115 3.6 3.6 62 15 21 255 274 +0.125 V V mA mA mA mA mA mW mW mW mW %FSR/V
7
ISL5827 Typical Performance (+3.3V Supply, Using Figure 13 with RDIFF = 100 and RLOAD = 50)
SPECTRAL MASK FOR GSM900/DCS1800/PCS1900 P>43dBm NORMAL BTS WITH 30kHz RBW
FIGURE 1. EDGE AT 11MHz, 78MSPS CLOCK (91+dBc @ f = +6MHz)
FIGURE 2. EDGE AT 11MHz, 78MSPS CLOCK (75dBc -NYQUIST, 6dB PAD)
SPECTRAL MASK FOR GSM900/DCS1800/PCS1900 P>43dBm NORMAL BTS WITH 30kHz RBW
FIGURE 3. GSM AT 11MHz, 78MSPS CLOCK (90+dBc @ f = +6MHz, 3dB PAD)
FIGURE 4. GSM AT 11MHz, 78MSPS CLOCK (75dBc - NYQUIST, 9dB PAD)
FIGURE 5. FOUR EDGE CARRIERS AT 12.4-15.6MHz, 800kHz SPACING, 78MSPS (71dBc - 20MHz WINDOW)
FIGURE 6. FOUR GSM CARRIERS AT 12.4-15.6MHz, 78MSPS (73dBc - 20MHz WINDOW, 6dB PAD)
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ISL5827 Typical Performance (+3.3V Supply, Using Figure 13 with RDIFF = 100 and RLOAD = 50)
(Continued)
SPECTRAL MASK UMTS TDD P>43dBm BTS
FIGURE 7. UMTS AT 19.2MHz, 76.8MSPS (70dB 1st ACPR, 70dB 2nd ACPR)
FIGURE 8. ONE TONE AT 10.1MHz, 80MSPS CLOCK (71dBc - NYQUIST, 6dB PAD)
FIGURE 9. ONE TONE AT 40.4MHz, 210MSPS CLOCK (61dBc - NYQUIST, 6dB PAD)
FIGURE 10. EIGHT TONES (CREST FACTOR = 8.9) AT 37MHz, 210MSPS CLOCK, 2.1MHz SPACING (65dBc - NYQUIST)
FIGURE 11. TWO TONES (CF = 6) AT 8.5MHz, 50MSPS CLOCK, 500kHz SPACING (82dBc - 10MHz WINDOW, 6dB PAD)
FIGURE 12. FOUR TONES (CF = 8.1) AT 14MHz, 80MSPS CLOCK, 800kHz SPACING (70dBc - NYQUIST, 6dB PAD)
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ISL5827 Definition of Specifications
Adjacent Channel Power Ratio, ACPR, is the ratio of the average power in the adjacent frequency channel (or offset) to the average power in the transmitted frequency channel. Crosstalk, is the measure of the channel isolation from one DAC to the other. It is measured by generating a sinewave in one DAC while the other DAC is clocked with a static input, and comparing the output power of each DAC at the frequency generated. Differential Linearity Error, DNL, is the measure of the step size output deviation from code to code. Ideally the step size should be one LSB. A DNL specification of one LSB or less guarantees monotonicity. EDGE, Enhanced Data for Global Evolution, a TDMA standard for cellular applications which uses 200kHz BW, 8-PSK modulated carriers. Full Scale Gain Drift, is measured by setting the data inputs to be all logic high (all 1s) and measuring the output voltage through a known resistance as the temperature is varied from TMIN to TMAX . It is defined as the maximum deviation from the value measured at room temperature to the value measured at either TMIN or TMAX . The units are ppm of FSR (full scale range) per C. Full Scale Gain Error, is the error from an ideal ratio of 32 between the output current and the full scale adjust current (through RSET). Gain Matching, is a measure of the full scale amplitude match between the I and Q channels given the same input pattern. It is typically measured with all 1s at the input to both channels, and the full scale output voltage developed into matching loads is compared for the I and Q outputs. GSM, Global System for Mobile Communication, a TDMA standard for cellular applications which uses 200kHz BW, GMSK modulated carriers. Integral Linearity Error, INL, is the measure of the worst case point that deviates from a best fit straight line of data values along the transfer curve. Internal Reference Voltage Drift, is defined as the maximum deviation from the value measured at room temperature to the value measured at either TMIN or TMAX . The units are ppm per C. Offset Drift, is measured by setting the data inputs to all logic low (all 0s) and measuring the output voltage at IOUTA through a known resistance as the temperature is varied from TMIN to TMAX . It is defined as the maximum deviation from the value measured at room temperature to the value measured at either TMIN or TMAX . The units are ppm of FSR (full scale range) per degree C. Offset Error, is measured by setting the data inputs to all logic low (all 0s) and measuring the output voltage of IOUTA through 10 a known resistance. Offset error is defined as the maximum deviation of the IOUTA output current from a value of 0mA. Output Voltage Compliance Range, is the voltage limit imposed on the output. The output impedance should be chosen such that the voltage developed does not violate the compliance range. Power Supply Rejection, is measured using a single power supply. The nominal supply voltage is varied 10% and the change in the DAC full scale output is noted. Reference Input Multiplying Bandwidth, is defined as the 3dB bandwidth of the voltage reference input. It is measured by using a sinusoidal waveform as the external reference with the digital inputs set to all 1s. The frequency is increased until the amplitude of the output waveform is 0.707 (-3dB) of its original value. Spurious Free Dynamic Range, SFDR, is the amplitude difference from the fundamental signal to the largest harmonically or non-harmonically related spur within the specified frequency window. Total Harmonic Distortion, THD, is the ratio of the RMS value of the fundamental output signal to the RMS sum of the first five harmonic components. UMTS, Universal Mobile Telecommunications System, a W-CDMA standard for cellular applications which uses 3.84MHz modulated carriers.
Detailed Description
The ISL5827 is a dual 12-bit, current out, CMOS, digital to analog converter. The maximum update rate is at least 260+MSPS and can be powered by a single power supply in the recommended range of +3.0V to +3.6V. It consumes less than 125mW of power per channel when using a +3.3V supply, the maximum 20mA of output current, and the data switching at 210MSPS. The architecture is based on a segmented current source arrangement that reduces glitch by reducing the amount of current switching at any one time. In previous architectures that contained all binary weighted current sources or a binary weighted resistor ladder, the converter might have a substantially larger amount of current turning on and off at certain, worst-case transition points such as midscale and quarter scale transitions. By greatly reducing the amount of current switching at these major transitions, the overall glitch of the converter is dramatically reduced, improving settling time, transient problems, and accuracy.
Digital Inputs and Termination
The ISL5827 digital inputs are formatted as offset binary and guaranteed to 3V LVCMOS levels. The internal register is updated on the rising edge of the clock. To minimize reflections, proper termination should be implemented. If the lines driving the clock and the digital inputs are long 50 lines, then 50 termination resistors should be placed as
ISL5827
close to the converter inputs as possible connected to the digital ground plane (if separate grounds are used). These termination resistors are not likely needed as long as the digital waveform source is within a few inches of the DAC. For pattern drivers with very high speed edge rates, it is recommended that the user consider series termination (50-200) prior to the DAC's inputs in order to reduce the amount of noise. If the full scale output current is set to 20mA by using the internal voltage reference (1.23V) and a 1.91k RSET resistor, then the input coding to output current will resemble the following:
TABLE 1. INPUT CODING vs OUTPUT CURRENT WITH INTERNAL REFERENCE (1.23V TYP) AND RSET = 1.91k INPUT CODE (D11-D0) 1111 1111 1111 1000 0000 0000 0000 0000 0000 IOUTA (mA) 20.6 10.3 0 IOUTB (mA) 0 10.3 20.6
Power Supply
Separate digital and analog power supplies are recommended. The allowable supply range is +2.7V to +3.6V. The recommended supply range is +3.0 to 3.6V (nominally +3.3V) to maintain optimum SFDR. However, operation down to +2.7V is possible with some degradation in SFDR. Reducing the analog output current can help the SFDR at +2.7V. The SFDR values stated in the table of specifications were obtained with a +3.3V supply.
Analog Output
IOUTA and IOUTB are complementary current outputs. The sum of the two currents is always equal to the full scale output current minus one LSB. If single ended use is desired, a load resistor can be used to convert the output current to a voltage. It is recommended that the unused output be either grounded or equally terminated. The voltage developed at the output must not violate the output voltage compliance range of -1.0V to 1.25V. ROUT (the impedance loading each current output) should be chosen so that the desired output voltage is produced in conjunction with the output full scale current. If a known line impedance is to be driven, then the output load resistor should be chosen to match this impedance. The output voltage equation is: VOUT = IOUT X ROUT. The most effective method for reducing the power consumption is to reduce the analog output current, which dominates the supply current. The maximum recommended output current is 20mA.
Ground Planes
Separate digital and analog ground planes should be used. All of the digital functions of the device and their corresponding components should be located over the digital ground plane and terminated to the digital ground plane. The same is true for the analog components and the analog ground plane.
Noise Reduction
To minimize power supply noise, 0.1F capacitors should be placed as close as possible to the converter's power supply pins, AVDD and DVDD . Also, the layout should be designed using separate digital and analog ground planes and these capacitors should be terminated to the digital ground for DVDD and to the analog ground for AVDD . Additional filtering of the power supplies on the board is recommended.
Voltage Reference
The internal voltage reference of the device has a nominal value of +1.23V with a 40ppm/C drift coefficient over the full temperature range of the converter. It is recommended that a 0.1F capacitor be placed as close as possible to the REFIO pin, connected to the analog ground. The REFLO pin selects the reference. The internal reference can be selected if REFLO is tied low (ground). If an external reference is desired, then REFLO should be tied high (the analog supply voltage) and the external reference driven into REFIO. The full scale output current of the converter is a function of the voltage reference used and the value of RSET. IOUT should be within the 2mA to 22mA range, though operation below 2mA is possible, with performance degradation. If the internal reference is used, VFSADJ will equal approximately 1.2V. If an external reference is used, VFSADJ will equal the external reference. The calculation for IOUT (Full Scale) is: IOUT(Full Scale) = (VFSADJ/RSET) X 32.
Differential Output
IOUTA and IOUTB can be used in a differential-to-singleended arrangement to achieve better harmonic rejection. With RDIFF = 50 and RLOAD = 50, the circuit in Figure 13 will provide a 500mV (-2.5dBm) signal at the output of the transformer if the full scale output current of the DAC is set to 20mA (used for the electrical specifications table). Values of RDIFF = 100 and RLOAD = 50 were used for the typical performance curves to increase the output power and the dynamic range. The center tap in Figure 13 must be grounded. In the circuit in Figure 14, the user is left with the option to ground or float the center tap. The DC voltage that will exist at either IOUTA or IOUTB if the center tap is floating is IOUTDC x (RA//RB) V because RDIFF is DC shorted by the transformer. If the center tap is grounded, the DC voltage is 0V. Recommended values for the circuit in Figure 14 are RA = RB = 50, RDIFF = 100, assuming RLOAD = 50. The performance of Figure 13 and Figure 14 is basically the same, however leaving the center tap of Figure 14 floating allows the circuit to find a more balanced virtual ground,
11
ISL5827
theoretically improving the even order harmonic rejection, but likely reducing the signal swing available due to the output voltage compliance range limitations.
REQ = 0.5 x (RLOAD//RDIFF) AT EACH OUTPUT VOUT = (2 x OUTA x REQ)V 1:1 RDIFF ISL5827 OUTB RLOAD ISL5827 REQ = 0.5 x (RLOAD//RDIFF//RA), WHERE RA = RB AT EACH OUTPUT RA OUTA RDIFF OUTB RB VOUT = (2 x OUTA x REQ)V RLOAD
OUTA
RLOAD REPRESENTS THE LOAD SEEN BY THE TRANSFORMER
FIGURE 14. ALTERNATIVE OUTPUT LOADING
RLOAD REPRESENTS THE LOAD SEEN BY THE TRANSFORMER
Propagation Delay
The converter requires two clock rising edges for data to be represented at the output. Each rising edge of the clock captures the present data word and outputs the previous data. The propagation delay is therefore 1/CLK, plus <2ns of processing. See Figure 15.
FIGURE 13. OUTPUT LOADING FOR DATASHEET MEASUREMENTS
Test Service
Intersil offers customer-specific testing of converters with a service called Testdrive. To submit a request, fill out the Testdrive form at www.intersil.com/testdrive. Or, send a request to the technical support center.
Timing Diagram
tPW1 tPW2
CLK tSU tHLD D11-D0 W0 W1 tSU tHLD W2 tSU tHLD W3
50%
tPD
tPD OUTPUT = W0
IOUT
OUTPUT = W-1
OUTPUT = W1
FIGURE 15. PROPAGATION DELAY, SETUP TIME, HOLD TIME AND MINIMUM PULSE WIDTH DIAGRAM
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ISL5827 Thin Plastic Quad Flatpack Packages (LQFP)
D D1 -D-
Q48.7x7A (JEDEC MS-026BBC ISSUE B) 48 LEAD THIN PLASTIC QUAD FLATPACK PACKAGE
INCHES SYMBOL A A1 MIN 0.002 0.054 0.007 0.007 0.350 0.272 0.350 0.272 0.018 48 0.020 BSC MAX 0.062 0.005 0.057 0.010 0.009 0.358 0.280 0.358 0.280 0.029 MILLIMETERS MIN 0.05 1.35 0.17 0.17 8.90 6.90 8.90 6.90 0.45 48 0.50 BSC MAX 1.60 0.15 1.45 0.27 0.23 9.10 7.10 9.10 7.10 0.75 NOTES 6 3 4, 5 3 4, 5 7 Rev. 2 1/99 NOTES: 1. Controlling dimension: MILLIMETER. Converted inch dimensions are not necessarily exact. 2. All dimensions and tolerances per ANSI Y14.5M-1982. 3. Dimensions D and E to be determined at seating plane -C- . 4. Dimensions D1 and E1 to be determined at datum plane -H- . 5. Dimensions D1 and E1 do not include mold protrusion. Allowable protrusion is 0.25mm (0.010 inch) per side. 6. Dimension b does not include dambar protrusion. Allowable dambar protrusion shall not cause the lead width to exceed the maximum b dimension by more than 0.08mm (0.003 inch). 7. "N" is the number of terminal positions.
-AE E1
-B-
A2 b b1 D D1 E
e
PIN 1 SEATING A PLANE 0.08 0.003 -C0.08 0.003 M 11o-13o 0.020 0.008 MIN 0o MIN GAGE PLANE L 0o-7o 0.25 0.010 11o-13o 0.09/0.16 A2 A1 0.004/0.006 BASE METAL WITH PLATING
E1 L N e
-H-
C A-B S
DS b b1
0.09/0.20 0.004/0.008
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