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LTC2220-1 12-Bit,185Msps ADC
FEATURES

DESCRIPTIO
Sample Rate: 185Msps 67.5dB SNR up to 140MHz Input 80dB SFDR up to 170MHz Input 775MHz Full Power Bandwidth S/H Single 3.3V Supply Low Power Dissipation: 910mW LVDS, CMOS, or Demultiplexed CMOS Outputs Selectable Input Ranges: 0.5V or 1V No Missing Codes Optional Clock Duty Cycle Stabilizer Shutdown and Nap Modes Data Ready Output Clock Pin Compatible Family 185Msps: LTC2220-1 (12-Bit) 170Msps: LTC2220 (12-Bit), LTC2230 (10-Bit) 135Msps: LTC2221 (12-Bit), LTC2231 (10-Bit) 64-Pin 9mm x 9mm QFN Package
The LTC(R)2220-1 is a 185Msps, sampling 12-bit A/D converter designed for digitizing high frequency, wide dynamic range signals. The LTC2220-1 is perfect for demanding communications applications with AC performance that includes 67.5dB SNR and 80dB spurious free dynamic range for signals up to 170MHz. Ultralow jitter of 0.15psRMS allows undersampling of IF frequencies with excellent noise performance. DC specs include 0.7LSB INL (typ), 0.5LSB DNL (typ) and no missing codes over temperature. The transition noise is a low 0.5LSBRMS. The digital outputs can be either differential LVDS, or single-ended CMOS. There are three format options for the CMOS outputs: a single bus running at the full data rate or two demultiplexed buses running at half data rate with either interleaved or simultaneous update. A separate output power supply allows the CMOS output swing to range from 0.5V to 3.6V. The ENC+ and ENC - inputs may be driven differentially or single ended with a sine wave, PECL, LVDS, TTL, or CMOS inputs. An optional clock duty cycle stabilizer allows high performance at full speed for a wide range of clock duty cycles.
APPLICATIO S

Wireless and Wired Broadband Communication Cable Head-End Systems Power Amplifier Linearization Communications Test Equipment
, LTC and LT are registered trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners.
TYPICAL APPLICATIO
3.3V REFH REFL FLEXIBLE REFERENCE
VDD 0.5V TO 3.6V OVDD
100 90 4th OR HIGHER
SFDR (dBFS)
+
ANALOG INPUT INPUT S/H
-
12-BIT PIPELINED ADC CORE
CORRECTION LOGIC
OUTPUT DRIVERS
D11 * * * D0
80 70 2nd OR 3rd 60 50 40
CMOS OR LVDS
OGND CLOCK/DUTY CYCLE CONTROL
22201 TA01
ENCODE INPUT
U
SFDR vs Input Frequency
0 100 200 300 400 500 600 INPUT FREQUENCY (MHz) 22201 TA01b
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LTC2220-1
ABSOLUTE
AXI U RATI GS
PACKAGE/ORDER I FOR ATIO
TOP VIEW
OVDD = VDD (Notes 1, 2)
Supply Voltage (VDD) ................................................. 4V Digital Output Ground Voltage (OGND) ....... -0.3V to 1V Analog Input Voltage (Note 3) ..... -0.3V to (VDD + 0.3V) Digital Input Voltage .................... -0.3V to (VDD + 0.3V) Digital Output Voltage ............... -0.3V to (OVDD + 0.3V) Power Dissipation ............................................ 1500mW Operating Temperature Range LTC2220-1C ............................................ 0C to 70C LTC2220-1I .........................................-40C to 85C Storage Temperature Range ..................-65C to 125C
AIN+ 1 AIN+ 2 AIN- 3 AIN- 4 REFHA 5 REFHA 6 REFLB 7 REFLB 8 REFHB 9 REFHB 10 REFLA 11 REFLA 12 VDD 13 VDD 14 VDD 15 GND 16
64 GND 63 VDD 62 VDD 61 GND 60 VCM 59 SENSE 58 MODE 57 LVDS 56 OF +/OFA 55 OF -/DA11 54 D11+/DA10 53 D11-/DA9 52 D10+/DA8 51 D10 -/DA7 50 OGND 49 OVDD
65
48 D9+/DA6 47 D9-/DA5 46 D8+/DA4 45 D8-/DA3 44 D7 +/DA2 43 D7 -/DA1 42 OVDD 41 OGND 40 D6+/DA0 39 D6-/CLOCKOUTA 38 D5+/CLOCKOUTB 37 D5-/OFB 36 CLOCKOUT +/DB11 35 CLOCKOUT -/DB10 34 OVDD 33 OGND
TJMAX = 125C, JA = 20C/W EXPOSED PAD (PIN 65) IS GND, MUST BE SOLDERED TO PCB
ORDER PART NUMBER LTC2220CUP-1 LTC2220IUP-1
Order Options Tape and Reel: Add #TR Lead Free: Add #PBF Lead Free Tape and Reel: Add #TRPBF Lead Free Part Marking: http://www.linear.com/leadfree/ Consult LTC Marketing for parts specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping container.
CO VERTER CHARACTERISTICS The denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25C. (Note 4)
PARAMETER Resolution (No Missing Codes) Integral Linearity Error Differential Linearity Error Integral Linearity Error Differential Linearity Error Offset Error Gain Error Offset Drift Full-Scale Drift Transition Noise Internal Reference External Reference SENSE = 1V Differential Analog Input (Note 5) Differential Analog Input Single-Ended Analog Input (Note 5) Single-Ended Analog Input (Note 6) External Reference

CONDITIONS

ENC + 17 ENC - 18 SHDN 19 OE 20 DO-/DB0 21 + DO /DB1 22 D1-/DB2 23 D1+/DB3 24 OGND 25 OVDD 26 D2-/DB4 27 +/DB5 28 D2 D3-/DB6 29 D3+/DB7 30 D4-/DB8 31 D4+/DB9 32
UP PACKAGE 64-LEAD (9mm x 9mm) PLASTIC QFN
UP PART MARKING* LTC2220UP-1
MIN 12 -1.8 -1
TYP 0.7 0.5 1.5 0.5
MAX 1.8 1.2
UNITS Bits LSB LSB LSB LSB
-35 -2.5
3 0.5 10 30 15 0.5
35 2.5
ppm/C ppm/C LSBRMS
2220_1fa
2
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mV %FS V/C
W
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LTC2220-1
The denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25C. (Note 4)
SYMBOL VIN VIN, CM IIN ISENSE IMODE ILVDS tAP tJITTER CMRR PARAMETER Analog Input Range (AIN+ - AIN-) Analog Input Common Mode (AIN + AIN Analog Input Leakage Current SENSE Input Leakage MODE Pin Pull-Down Current to GND LVDS Pin Pull-Down Current to GND Sample and Hold Acquisition Delay Time Sample and Hold Acquisition Delay Time Jitter Analog Input Common Mode Rejection Ratio Full Power Bandwidth Figure 8 Test Circuit
+ -)/2
A ALOG I PUT
DY A IC ACCURACY
SYMBOL SNR PARAMETER
The denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25C. AIN = -1dBFS. (Note 4)
CONDITIONS 5MHz Input (1V Range) 5MHz Input (2V Range) 70MHz Input (1V Range) 70MHz Input (2V Range) 140MHz Input (1V Range) 140MHz Input (2V Range) 250MHz Input (1V Range) 250MHz Input (2V Range)
Signal-to-Noise Ratio (Note 10)
SFDR
Spurious Free Dynamic Range 2nd or 3rd Harmonic (Note 11)
SFDR
Spurious Free Dynamic Range 4th Harmonic or Higher (Note 11)
S/(N+D)
Signal-to-Noise Plus Distortion Ratio (Note 12)
IMD
Intermodulation Distortion
U
WU
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CONDITIONS 3.1V < VDD < 3.5V (Note 7) Differential Input (Note 7) Single Ended Input (Note 7) 0 < AIN+, AIN- < VDD 0V < SENSE < 1V

MIN 1 0.5 -1 -1
TYP 0.5 to 1 1.6 1.6
MAX 1.9 2.1 1 1
UNITS V V V A A A A ns psRMS dB MHz
10 10 0 0.15 80 775
MIN
TYP 62.7 67.7
MAX
UNITS dB dB dB dB dB dB dB dB dB dB dB dB dB dB dB dB dB dB dB dB dB dB dB dB dB dB dB dB dBc
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65.2
62.7 67.6 62.4 67.5 61.8 66.1 80 80
5MHz Input (1V Range) 5MHz Input (2V Range) 70MHz Input (1V Range) 70MHz Input (2V Range) 140MHz Input (1V Range) 140MHz Input (2V Range) 250MHz Input (1V Range) 250MHz Input (2V Range) 5MHz Input (1V Range) 5MHz Input (2V Range) 70MHz Input (1V Range) 70MHz Input (2V Range) 140MHz Input (1V Range) 140MHz Input (2V Range) 250MHz Input (1V Range) 250MHz Input (2V Range) 5MHz Input (1V Range) 5MHz Input (2V Range) 70MHz Input (1V Range) 70MHz Input (2V Range) fIN1 = 138MHz, fIN2 = 140MHz

69
80 80 80 80 74 73 85 85
74
85 85 84 84 83 83 62.7 67.5
64.2
62.7 67.3 81
3
LTC2220-1
I TER AL REFERE CE CHARACTERISTICS (Note 4)
PARAMETER VCM Output Voltage VCM Output Tempco VCM Line Regulation VCM Output Resistance 3.1V < VDD < 3.5V -1mA < IOUT < 1mA CONDITIONS IOUT = 0 MIN 1.570 TYP 1.600 25 3 4 MAX 1.630 UNITS V ppm/C mV/V
DIGITAL I PUTS A D DIGITAL OUTPUTS
SYMBOL VID VICM RIN CIN VIH VIL IIN CIN OVDD = 3.3V COZ ISOURCE ISINK VOH VOL OVDD = 2.5V VOH VOL OVDD = 1.8V VOH VOL VOD VOS High Level Output Voltage Low Level Output Voltage Differential Output Voltage Output Common Mode Voltage IO = -200A IO = 1.6mA 100 Differential Load 100 Differential Load High Level Output Voltage Low Level Output Voltage IO = -200A IO = 1.6mA Hi-Z Output Capacitance Output Source Current Output Sink Current High Level Output Voltage Low Level Output Voltage OE = High (Note 7) VOUT = 0V VOUT = 3.3V IO = -10A IO = -200A IO = 10A IO = 1.6mA PARAMETER Differential Input Voltage Common Mode Input Voltage Input Resistance Input Capacitance High Level Input Voltage Low Level Input Voltage Input Current Input Capacitance (Note 7) VDD = 3.3V VDD = 3.3V VIN = 0V to VDD (Note 7) Internally Set Externally Set (Note 7) CONDITIONS ENCODE INPUTS (ENC +, ENC -)
The denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25C. (Note 4)
MIN

LOGIC INPUTS (OE, SHDN)

LOGIC OUTPUTS (CMOS MODE) 3 50 50

LOGIC OUTPUTS (LVDS MODE)

4
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U
U
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TYP
MAX
UNITS V
0.2 1.1 1.6 1.6 6 3 2 0.8 -10 3 10 2.5
V V k pF V V A pF
pF mA mA V V 0.4 V V V V V V 454 1.375 mV V
3.1
3.295 3.29 0.005 0.09 2.49 0.09 1.79 0.09
247 1.125
350 1.250
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LTC2220-1
POWER REQUIRE E TS
SYMBOL VDD PSHDN PNAP LVDS OUTPUT MODE OVDD IVDD IOVDD PDISS OVDD IVDD PDISS Output Supply Voltage Analog Supply Current Output Supply Current Power Dissipation Output Supply Voltage Analog Supply Current Power Dissipation PARAMETER Analog Supply Voltage Shutdown Power Nap Mode Power
The denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25C. (Note 9)
CONDITIONS (Note 8) SHDN = High, OE = High, No CLK SHDN = High, OE = Low, No CLK (Note 8)

CMOS OUTPUT MODE (Note 8)

TI I G CHARACTERISTICS
SYMBOL fS tL tH tAP tOE tD tC PARAMETER Sampling Frequency ENC Low Time (Note 7) ENC High Time (Note 7) Sample-and-Hold Aperture Delay Output Enable Delay ENC to DATA Delay ENC to CLOCKOUT Delay DATA to CLOCKOUT Skew Rise Time Fall Time Pipeline Latency CMOS OUTPUT MODE tD tC Pipeline Latency ENC to DATA Delay ENC to CLOCKOUT Delay DATA to CLOCKOUT Skew Full Rate CMOS Demuxed Interleaved Demuxed Simultaneous
The denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25C. (Note 4)
CONDITIONS (Note 8) Duty Cycle Stabilizer Off Duty Cycle Stabilizer On Duty Cycle Stabilizer Off Duty Cycle Stabilizer On (Note 7) (Note 7) (Note 7) (tC - tD) (Note 7)

LVDS OUTPUT MODE 1.3 1.3 -0.6 2.2 2.2 0 0.5 0.5 5 (Note 7) (Note 7) (tC - tD) (Note 7)

UW
MIN 3.1
TYP 3.3 2 35
MAX 3.5
UNITS V mW mW
3
3.3 273 55 1080
3.6 300 70 1221 3.6 300
V mA mA mW V mA mW
0.5
3.3 273 910
UW
MIN 1 2.5 2 2.5 2
TYP 2.7 2.7 2.7 2.7 0 5
MAX 185 500 500 500 500 10 3.5 3.5 0.6
UNITS MHz ns ns ns ns ns ns ns ns ns ns ns ns
1.3 1.3 -0.6
2.1 2.1 0 5 5 5 and 6
3.5 3.5 0.6
ns ns ns Cycles Cycles Cycles
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LTC2220-1
ELECTRICAL CHARACTERISTICS
Note 1: Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device. Exposure to any Absolute Maximum Rating condition for extended periods may affect device reliability and lifetime. Note 2: All voltage values are with respect to ground with GND and OGND wired together (unless otherwise noted). Note 3: When these pin voltages are taken below GND or above VDD, they will be clamped by internal diodes. This product can handle input currents of greater than 100mA below GND or above VDD without latchup. Note 4: VDD = 3.3V, fSAMPLE = 185MHz, LVDS outputs, differential ENC+/ENC- = 2VP-P sine wave, input range = 2VP-P with differential drive, unless otherwise noted. Note 5: Integral nonlinearity is defined as the deviation of a code from a "best straight line" fit to the transfer curve. The deviation is measured from the center of the quantization band. Note 6: Offset error is the offset voltage measured from -0.5 LSB when the output code flickers between 0000 0000 0000 and 1111 1111 1111 in 2's complement output mode. Note 7: Guaranteed by design, not subject to test. Note 8: Recommended operating conditions. Note 9: VDD = 3.3V, fSAMPLE = 185MHz, differential ENC+/ENC- = 2VP-P sine wave, input range = 1VP-P with differential drive, output CLOAD = 5pF. Note 10: SNR minimum and typical values are for LVDS mode. Typical values for CMOS mode are typically 0.3dB lower. Note 11: SFDR minimum values are for LVDS mode. Typical values are for both LVDS and CMOS modes. Note 12: SINAD minimum and typical values are for LVDS mode. Typical values for CMOS mode are typically 0.3dB lower.
TYPICAL PERFOR A CE CHARACTERISTICS
LTC2220-1: INL, 2V Range
1.0 0.8 0.6 0.4 1.0 0.8 0.6 0.4
ERROR (LSB)
ERROR (LSB)
0 - 0.2 - 0.4 - 0.6 - 0.8 - 1.0 0 1024 3072 2048 OUTPUT CODE 4096
2220 G01
0 - 0.2 - 0.4 - 0.6 - 0.8 - 1.0 0 1024 3072 2048 OUTPUT CODE 4096
2220 G02
COUNT
0.2
LTC2220-1: SNR vs Input Frequency, -1dB, 2V Range, LVDS Mode
70 69 68 67
66 65 64 63 62 61 60 0 100 400 500 INPUT FREQUENCY (MHz) 200 300 600
2220 G04
66 65 64 63 62 61 60 0 100 400 500 INPUT FREQUENCY (MHz) 200 300 600
2220 G05
SFDR (dBFS)
SNR (dBFS)
SNR (dBFS)
6
UW
(TA = 25C unless otherwise noted, Note 4) LTC2220-1: Shorted Input Noise Histogram
100000 93571
LTC2220-1: DNL, 2V Range
80000
0.2
60000
40000 24266 20000 229 -0 2056 2057 2058 CODE 2059 2060
2220 G03
12866 140
LTC2220-1: SNR vs Input Frequency, -1dB, 1V Range, LVDS Mode
70 69 68 67
100 90 80 70 60 50 40
LTC2220-1: SFDR (HD2 and HD3) vs Input Frequency, -1dB, 2V Range, LVDS Mode
0
100
200 300 400 500 INPUT FREQUENCY (MHz)
600
2220 G06
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LTC2220-1 TYPICAL PERFOR A CE CHARACTERISTICS
LTC2220-1: SFDR (HD2 and HD3) vs Input Frequency, -1dB, 1V Range, LVDS Mode
100 90 80 70 60 50 40 100 90 80 70 60 50 40
SFDR (dBFS)
SFDR (dBFS)
SFDR (dBFS)
200 300
0
100
400 500 600 INPUT FREQUENCY (MHz) 2220 G07
200
300
LTC2220-1: SFDR and SNR vs Sample Rate, 1V Range, fIN = 30MHz, -1dB, LVDS Mode
95 90 85 SFDR
SFDR AND SNR (dBFS)
SFDR AND SNR (dBFS)
IVDD (mA)
80 75 70 65 60 55 50 0 40 120 160 SAMPLE RATE (Msps) 80 200
2220 G10
SNR
LTC2220-1: IOVDD vs Sample Rate, 5MHz Sine Wave Input, -1dB
60 50 40 LVDS OUTPUTS, 0VDD = 3.3V
SFDR (dBc AND dBFS)
IOVDD (mA)
30 20 CMOS OUTPUTS, 0VDD = 1.8V 10 0 0 40
UW
LTC2220-1: SFDR (HD4+) vs Input Frequency, -1dB, 2V Range, LVDS Mode
100 90 80 70 60 50 40
LTC2220-1: SFDR (HD4+) vs Input Frequency, -1dB, 1V Range, LVDS Mode
0
100
400 500 600 INPUT FREQUENCY (MHz) 2220 G08
0
100
200 300 400 500 INPUT FREQUENCY (MHz)
600
2220 G09
LTC2220-1: SFDR and SNR vs Sample Rate, 2V Range, fIN = 30MHz, -1dB, LVDS Mode
95 90 85 80 75 70 65 60 55 50 0 40 120 160 SAMPLE RATE (Msps) 80 200
2220 G11
LTC2220-1: IVDD vs Sample Rate, 5MHz Sine Wave Input, -1dB
290 280 270 260 250 240 230 220 210 0 40 80 120 160 SAMPLE RATE (Msps) 200
2220 G12
SFDR
2V RANGE 1V RANGE
SNR
LTC2220-1: SFDR vs Input Level, f IN = 70MHz, 2V Range
100 90 80 70 60 50 40 30 20 10 dBFS dBc
120 160 SAMPLE RATE (Msps)
80
200
2220 G13
0 -60
-50
-30 -20 -40 INPUT LEVEL (dBFS)
-10
0
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2220 G14
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LTC2220-1 TYPICAL PERFOR A CE CHARACTERISTICS
LTC2220-1: 8192 Point FFT, f IN = 5MHz, -1dB, 2V Range, LVDS Mode
0 -20 AMPLITUDE (dB) AMPLITUDE (dB) -40 -60 -80 0 -20 -40 -60 -80 AMPLITUDE (dB)
-100 -120 0 10 20 30 40 50 60 70 80 90 2220 G15 FREQUENCY (MHz)
LTC2220-1: 8192 Point FFT, f IN = 250MHz, -1dB, 2V Range, LVDS Mode
0 -20
AMPLITUDE (dB)
-40 -60 -80
AMPLITUDE (dB)
-100 -120 0 10 20 30 40 50 60 70 80 90 2220 G18 FREQUENCY (MHz)
8
UW
LTC2220-1: 8192 Point FFT, f IN = 70MHz, -1dB, 2V Range, LVDS Mode
0 -20 -40 -60 -80
LTC2220-1: 8192 Point FFT, f IN = 140MHz, -1dB, 2V Range, LVDS Mode
-100 -120 0 10 20 30 40 50 60 70 80 90 2220 G16 FREQUENCY (MHz)
-100 -120 0 10 20 30 40 50 60 70 80 90 2220 G17 FREQUENCY (MHz)
LTC2220-1: 8192 Point FFT, f IN = 500MHz, -6dB, 1V Range, LVDS Mode
0 -20 -40 -60 -80
-100 -120 0 10 20 30 40 50 60 70 80 90 2220 G19 FREQUENCY (MHz)
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LTC2220-1
PI FU CTIO S
(CMOS Mode) AIN+ (Pins 1, 2): Positive Differential Analog Input. AIN - (Pins 3, 4): Negative Differential Analog Input. REFHA (Pins 5, 6): ADC High Reference. Bypass to Pins 7, 8 with 0.1F ceramic chip capacitor, to Pins 11, 12 with a 2.2F ceramic capacitor and to ground with 1F ceramic capacitor. REFLB (Pins 7, 8): ADC Low Reference. Bypass to Pins 5, 6 with 0.1F ceramic chip capacitor. Do not connect to Pins 11, 12. REFHB (Pins 9, 10): ADC High Reference. Bypass to Pins 11, 12 with 0.1F ceramic chip capacitor. Do not connect to Pins 5, 6. REFLA (Pins 11, 12): ADC Low Reference. Bypass to Pins 9, 10 with 0.1F ceramic chip capacitor, to Pins 5, 6 with a 2.2F ceramic capacitor and to ground with 1F ceramic capacitor. VDD (Pins 13, 14, 15, 62, 63): 3.3V Supply. Bypass to GND with 0.1F ceramic chip capacitors. GND (Pins 16, 61, 64): ADC Power Ground. ENC+ (Pin 17): Encode Input. Conversion starts on the positive edge. ENC - (Pin 18): Encode Complement Input. Conversion starts on the negative edge. Bypass to ground with 0.1F ceramic for single-ended ENCODE signal. SHDN (Pin 19): Shutdown Mode Selection Pin. Connecting SHDN to GND and OE to GND results in normal operation with the outputs enabled. Connecting SHDN to GND and OE to VDD results in normal operation with the outputs at high impedance. Connecting SHDN to VDD and OE to GND results in nap mode with the outputs at high impedance. Connecting SHDN to VDD and OE to VDD results in sleep mode with the outputs at high impedance. OE (Pin 20): Output Enable Pin. Refer to SHDN pin function. DB0 - DB11 (Pins 21, 22, 23, 24, 27, 28, 29, 30, 31, 32, 35, 36): Digital Outputs, B Bus. DB11 is the MSB. At high impedance in full rate CMOS mode. OGND (Pins 25, 33, 41, 50): Output Driver Ground. OVDD (Pins 26, 34, 42, 49): Positive Supply for the Output Drivers. Bypass to ground with 0.1F ceramic chip capacitor. OFB (Pin 37): Over/Under Flow Output for B Bus. High when an over or under flow has occurred. At high impedance in full rate CMOS mode. CLKOUTB (Pin 38): Data Valid Output for B Bus. In demux mode with interleaved update, latch B bus data on the falling edge of CLKOUTB. In demux mode with simultaneous update, latch B bus data on the rising edge of CLKOUTB. This pin does not become high impedance in full rate CMOS mode. CLKOUTA (Pin 39): Data Valid Output for A Bus. Latch A bus data on the falling edge of CLKOUTA. DA0 - DA11 (Pins 40, 43, 44, 45, 46, 47, 48, 51, 52, 53, 54, 55): Digital Outputs, A Bus. DA11 is the MSB. OFA (Pin 56): Over/Under Flow Output for A Bus. High when an over or under flow has occurred. LVDS (Pin 57): Output Mode Selection Pin. Connecting LVDS to 0V selects full rate CMOS mode. Connecting LVDS to 1/3VDD selects demux CMOS mode with simultaneous update. Connecting LVDS to 2/3VDD selects demux CMOS mode with interleaved update. Connecting LVDS to VDD selects LVDS mode. MODE (Pin 58): Output Format and Clock Duty Cycle Stabilizer Selection Pin. Connecting MODE to 0V selects offset binary output format and turns the clock duty cycle stabilizer off. Connecting MODE to 1/3VDD selects offset binary output format and turns the clock duty cycle stabilizer on. Connecting MODE to 2/3VDD selects 2's complement output format and turns the clock duty cycle stabilizer on. Connecting MODE to VDD selects 2's complement output format and turns the clock duty cycle stabilizer off. SENSE (Pin 59): Reference Programming Pin. Connecting SENSE to VCM selects the internal reference and a 0.5V input range. Connecting SENSE to VDD selects the internal reference and a 1V input range. An external reference greater than 0.5V and less than 1V applied to SENSE selects an input range of VSENSE. 1V is the largest valid input range. VCM (Pin 60): 1.6V Output and Input Common Mode Bias. Bypass to ground with 2.2F ceramic chip capacitor. GND (Exposed Pad): ADC Power Ground. The exposed pad on the bottom of the package needs to be soldered to ground.
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LTC2220-1
PI FU CTIO S
(LVDS Mode) AIN+ (Pins 1, 2): Positive Differential Analog Input. AIN- (Pins 3, 4): Negative Differential Analog Input. REFHA (Pins 5, 6): ADC High Reference. Bypass to Pins 7, 8 with 0.1F ceramic chip capacitor, to Pins 11, 12 with a 2.2F ceramic capacitor and to ground with 1F ceramic capacitor. REFLB (Pins 7, 8): ADC Low Reference. Bypass to Pins 5, 6 with 0.1F ceramic chip capacitor. Do not connect to Pins 11, 12. REFHB (Pins 9, 10): ADC High Reference. Bypass to Pins 11, 12 with 0.1F ceramic chip capacitor. Do not connect to Pins 5, 6. REFLA (Pins 11, 12): ADC Low Reference. Bypass to Pins 9, 10 with 0.1F ceramic chip capacitor, to Pins 5, 6 with a 2.2F ceramic capacitor and to ground with 1F ceramic capacitor. VDD (Pins 13, 14, 15, 62, 63): 3.3V Supply. Bypass to GND with 0.1F ceramic chip capacitors. GND (Pins 16, 61, 64): ADC Power Ground. ENC+ (Pin 17): Encode Input. Conversion starts on the positive edge. ENC- (Pin 18): Encode Complement Input. Conversion starts on the negative edge. Bypass to ground with 0.1F ceramic for single-ended ENCODE signal. SHDN (Pin 19): Shutdown Mode Selection Pin. Connecting SHDN to GND and OE to GND results in normal operation with the outputs enabled. Connecting SHDN to GND and OE to VDD results in normal operation with the outputs at high impedance. Connecting SHDN to VDD and OE to GND results in nap mode with the outputs at high impedance. Connecting SHDN to VDD and OE to VDD results in sleep mode with the outputs at high impedance. OE (Pin 20): Output Enable Pin. Refer to SHDN pin function. D0-/D0+ to D11-/D11+ (Pins 21, 22, 23, 24, 27, 28, 29, 30, 31, 32, 37, 38, 39, 40, 43, 44, 45, 46, 47, 48, 51, 52, 53, 54): LVDS Digital Outputs. All LVDS outputs require differential 100 termination resistors at the LVDS receiver. D11-/D11+ is the MSB. OGND (Pins 25, 33, 41, 50): Output Driver Ground. OVDD (Pins 26, 34, 42, 49): Positive Supply for the Output Drivers. Bypass to ground with 0.1F ceramic chip capacitor. CLKOUT-/CLKOUT+ (Pins 35 to 36): LVDS Data Valid Output. Latch data on rising edge of CLKOUT-, falling edge of CLKOUT+. OF-/OF+ (Pins 55 to 56): LVDS Over/Under Flow Output. High when an over or under flow has occurred. LVDS (Pin 57): Output Mode Selection Pin. Connecting LVDS to 0V selects full rate CMOS mode. Connecting LVDS to 1/3VDD selects demux CMOS mode with simultaneous update. Connecting LVDS to 2/3VDD selects demux CMOS mode with interleaved update. Connecting LVDS to VDD selects LVDS mode. MODE (Pin 58): Output Format and Clock Duty Cycle Stabilizer Selection Pin. Connecting MODE to 0V selects offset binary output format and turns the clock duty cycle stabilizer off. Connecting MODE to 1/3VDD selects offset binary output format and turns the clock duty cycle stabilizer on. Connecting MODE to 2/3VDD selects 2's complement output format and turns the clock duty cycle stabilizer on. Connecting MODE to VDD selects 2's complement output format and turns the clock duty cycle stabilizer off. SENSE (Pin 59): Reference Programming Pin. Connecting SENSE to VCM selects the internal reference and a 0.5V input range. Connecting SENSE to VDD selects the internal reference and a 1V input range. An external reference greater than 0.5V and less than 1V applied to SENSE selects an input range of VSENSE. 1V is the largest valid input range. VCM (Pin 60): 1.6V Output and Input Common Mode Bias. Bypass to ground with 2.2F ceramic chip capacitor. GND (Exposed Pad): ADC Power Ground. The exposed pad on the bottom of the package needs to be soldered to ground.
10
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LTC2220-1
FUNCTIONAL BLOCK DIAGRA
AIN+ INPUT S/H FIRST PIPELINED ADC STAGE
AIN-
SECOND PIPELINED ADC STAGE
VCM 2.2F
1.6V REFERENCE RANGE SELECT SHIFT REGISTER AND CORRECTION
SENSE
REF BUF
REFH
DIFF REF AMP
REFLB REFHA 2.2F 0.1F 1F
Figure 1. Functional Block Diagram
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VDD THIRD PIPELINED ADC STAGE FOURTH PIPELINED ADC STAGE FIFTH PIPELINED ADC STAGE GND REFL INTERNAL CLOCK SIGNALS OVDD DIFFERENTIAL INPUT LOW JITTER CLOCK DRIVER CONTROL LOGIC OUTPUT DRIVERS * * *
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+ OF - + D11 - + - + -
D0 CLKOUT
REFLA REFHB 0.1F 1F ENC+ ENC- M0DE LVDS SHDN OE
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OGND
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LTC2220-1
TI I G DIAGRA S
LVDS Output Mode Timing All Outputs Are Differential and Have LVDS Levels
tAP ANALOG INPUT N tH tL ENC - ENC + tD D0-D11, OF tC N-5 N-4 N-3 N-2 N-1 N+1 N+2 N+3 N+4
CLOCKOUT - CLOCKOUT +
ANALOG INPUT
ENC - ENC + tD DA0-DA11, OFA tC CLOCKOUTB CLOCKOUTA N-5 N-4 N-3 N-2 N-1
DB0-DB11, OFB
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22201 TD01
Full-Rate CMOS Output Mode Timing All Outputs Are Single-Ended and Have CMOS Levels
tAP N tH tL N+1 N+2 N+3 N+4
HIGH IMPEDANCE
22201 TD02
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TI I G DIAGRA S
Demultiplexed CMOS Outputs with Interleaved Update All Outputs Are Single-Ended and Have CMOS Levels
tAP ANALOG INPUT N tH tL ENC - ENC + tD DA0-DA11, OFA N-5 tD DB0-DB11, OFB N-6 tC CLOCKOUTB CLOCKOUTA
22201 TD03
ANALOG INPUT
ENC - ENC + tD DA0-DA11, OFA tD DB0-DB11, OFB tC CLOCKOUTB CLOCKOUTA
22201 TD04
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N+2 N+3 N+1
N+4
N-3
N-1
N-4 tC
N-2
Demultiplexed CMOS Outputs with Simultaneous Update All Outputs Are Single-Ended and Have CMOS Levels
tAP N tH tL N+1 N+2 N+3 N+4
N-6
N-4
N-2
N-5
N-3
N-1
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LTC2220-1
APPLICATIO S I FOR ATIO
DYNAMIC PERFORMANCE Signal-to-Noise Plus Distortion Ratio The signal-to-noise plus distortion ratio [S/(N + D)] is the ratio between the RMS amplitude of the fundamental input frequency and the RMS amplitude of all other frequency components at the ADC output. The output is band limited to frequencies above DC to below half the sampling frequency. Signal-to-Noise Ratio The signal-to-noise ratio (SNR) is the ratio between the RMS amplitude of the fundamental input frequency and the RMS amplitude of all other frequency components except the first five harmonics and DC. Total Harmonic Distortion Total harmonic distortion is the ratio of the RMS sum of all harmonics of the input signal to the fundamental itself. The out-of-band harmonics alias into the frequency band between DC and half the sampling frequency. THD is expressed as: THD = 20Log ((V2 + V3 + V4 + . . . Vn )/V1) where V1 is the RMS amplitude of the fundamental frequency and V2 through Vn are the amplitudes of the second through nth harmonics. The THD calculated in this data sheet uses all the harmonics up to the fifth. Intermodulation Distortion If the ADC input signal consists of more than one spectral component, the ADC transfer function nonlinearity can produce intermodulation distortion (IMD) in addition to THD. IMD is the change in one sinusoidal input caused by the presence of another sinusoidal input at a different frequency. If two pure sine waves of frequencies fa and fb are applied to the ADC input, nonlinearities in the ADC transfer function can create distortion products at the sum and difference frequencies of mfa nfb, where m and n = 0, 1, 2, 3, etc. The 3rd order intermodulation products are 2fa + fb, 2fb + fa, 2fa - fb and 2fb - fa. The intermodulation distortion is defined as the ratio of the RMS value of either
2 2 2 2
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input tone to the RMS value of the largest 3rd order intermodulation product. Spurious Free Dynamic Range (SFDR) Spurious free dynamic range is the peak harmonic or spurious noise that is the largest spectral component excluding the input signal and DC. This value is expressed in decibels relative to the RMS value of a full scale input signal. Full Power Bandwidth The full power bandwidth is that input frequency at which the amplitude of the reconstructed fundamental is reduced by 3dB for a full scale input signal. Aperture Delay Time The time from when a rising ENC+ equals the ENC- voltage to the instant that the input signal is held by the sample and hold circuit. Aperture Delay Jitter The variation in the aperture delay time from conversion to conversion. This random variation will result in noise when sampling an AC input. The signal to noise ratio due to the jitter alone will be: SNRJITTER = -20log (2 * fIN * tJITTER) CONVERTER OPERATION As shown in Figure 1, the LTC2220-1 is a CMOS pipelined multistep converter. The converter has five pipelined ADC stages; a sampled analog input will result in a digitized value five cycles later (see the Timing Diagram section). For optimal AC performance the analog inputs should be driven differentially. For cost sensitive applications, the analog inputs can be driven single-ended with slightly worse harmonic distortion. The encode input is differential for improved common mode noise immunity. The LTC2220-1 has two phases of operation, determined by the state of the differential ENC+/ENC- input pins. For brevity, the text will refer to ENC+ greater than ENC- as ENC high and ENC+ less than ENC- as ENC low.
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Each pipelined stage shown in Figure 1 contains an ADC, a reconstruction DAC and an interstage residue amplifier. In operation, the ADC quantizes the input to the stage and the quantized value is subtracted from the input by the DAC to produce a residue. The residue is amplified and output by the residue amplifier. Successive stages operate out of phase so that when the odd stages are outputting their residue, the even stages are acquiring that residue and vice versa. When ENC is low, the analog input is sampled differentially directly onto the input sample-and-hold capacitors, inside the "Input S/H" shown in the block diagram. At the instant that ENC transitions from low to high, the sampled input is held. While ENC is high, the held input voltage is buffered by the S/H amplifier which drives the first pipelined ADC stage. The first stage acquires the output of the S/H during this high phase of ENC. When ENC goes back low, the first stage produces its residue which is acquired by the second stage. At the same time, the input S/H goes back to acquiring the analog input. When ENC goes back high, the second stage produces its residue which is acquired by the third stage. An identical process is repeated for the third and fourth stages, resulting in a fourth stage residue that is sent to the fifth stage ADC for final evaluation. Each ADC stage following the first has additional range to accommodate flash and amplifier offset errors. Results from all of the ADC stages are digitally synchronized such that the results can be properly combined in the correction logic before being sent to the output buffer. SAMPLE/HOLD OPERATION AND INPUT DRIVE Sample/Hold Operation Figure 2 shows an equivalent circuit for the LTC2220-1 CMOS differential sample-and-hold. The analog inputs are connected to the sampling capacitors (CSAMPLE) through NMOS transistors. The capacitors shown attached to each input (CPARASITIC) are the summation of all other capacitance associated with each input. During the sample phase when ENC is low, the transistors connect the analog inputs to the sampling capacitors and they charge to, and track the differential input voltage.
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When ENC transitions from low to high, the sampled input voltage is held on the sampling capacitors. During the hold phase when ENC is high, the sampling capacitors are disconnected from the input and the held voltage is passed to the ADC core for processing. As ENC transitions from high to low, the inputs are reconnected to the sampling capacitors to acquire a new sample. Since the sampling capacitors still hold the previous sample, a charging glitch proportional to the change in voltage between samples will be seen at this time. If the change between the last sample and the new sample is small, the charging glitch seen at the input will be small. If the input change is large, such as the change seen with input frequencies near Nyquist, then a larger charging glitch will be seen.
LTC2220-1 VDD 15 CPARASITIC 1pF CSAMPLE 1.6pF CPARASITIC 1pF VDD CSAMPLE 1.6pF AIN+ VDD 15 AIN- 1.6V 6k ENC+ ENC- 6k 1.6V
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Figure 2. Equivalent Input Circuit
Single-Ended Input For cost sensitive applications, the analog inputs can be driven single-ended. With a single-ended input the harmonic distortion and INL will degrade, but the SNR and DNL will remain unchanged. For a single-ended input, AIN+ should be driven with the input signal and AIN- should be connected to 1.6V or VCM. Common Mode Bias For optimal performance the analog inputs should be driven differentially. Each input should swing 0.5V for
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the 2V range or 0.25V for the 1V range, around a common mode voltage of 1.6V. The VCM output pin (Pin 60) may be used to provide the common mode bias level. VCM can be tied directly to the center tap of a transformer to set the DC input level or as a reference level to an op amp differential driver circuit. The VCM pin must be bypassed to ground close to the ADC with a 2.2F or greater capacitor. Input Drive Impedance As with all high performance, high speed ADCs, the dynamic performance of the LTC2220-1 can be influenced by the input drive circuitry, particularly the second and third harmonics. Source impedance and input reactance can influence SFDR. At the falling edge of ENC, the sampleand-hold circuit will connect the 1.6pF sampling capacitor to the input pin and start the sampling period. The sampling period ends when ENC rises, holding the sampled input on the sampling capacitor. Ideally the input circuitry should be fast enough to fully charge the sampling capacitor during the sampling period 1/(2FENCODE); however, this is not always possible and the incomplete settling may degrade the SFDR. The sampling glitch has been designed to be as linear as possible to minimize the effects of incomplete settling. For the best performance, it is recommended to have a source impedance of 100 or less for each input. The source impedance should be matched for the differential inputs. Poor matching will result in higher even order harmonics, especially the second. Input Drive Circuits Figure 3 shows the LTC2220-1 being driven by an RF transformer with a center tapped secondary. The secondary center tap is DC biased with VCM, setting the ADC input signal at its optimum DC level. Terminating on the transformer secondary is desirable, as this provides a common mode path for charging glitches caused by the sample and hold. Figure 3 shows a 1:1 turns ratio transformer. Other turns ratios can be used if the source impedance seen by the ADC does not exceed 100 for each ADC input. A disadvantage of using a transformer is the loss of low frequency response. Most small RF transformers have poor performance at frequencies below 1MHz.
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Figure 4 demonstrates the use of a differential amplifier to convert a single ended input signal into a differential input signal. The advantage of this method is that it provides low frequency input response; however, the limited gain bandwidth of most op amps will limit the SFDR at high input frequencies. Figure 5 shows a single-ended input circuit. The impedance seen by the analog inputs should be matched. This circuit is not recommended if low distortion is required. The 25 resistors and 12pF capacitor on the analog inputs serve two purposes: isolating the drive circuitry from the sample-and-hold charging glitches and limiting the wideband noise at the converter input. For input frequencies higher than 100MHz, the capacitor may need to be decreased to prevent excessive signal loss.
VCM 2.2F 0.1F ANALOG INPUT T1 1:1 25 25 25 0.1F AIN+ AIN+ 12pF 25 AIN- AIN-
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LTC2220-1
T1 = MA/COM ETC1-1T RESISTORS, CAPACITORS ARE 0402 PACKAGE SIZE
Figure 3. Single-Ended to Differential Conversion Using a Transformer
VCM HIGH SPEED DIFFERENTIAL AMPLIFIER 25 ANALOG INPUT 2.2F AIN+ AIN+ 12pF AIN- AIN- AMPLIFIER = LTC6600-20, LT1993, ETC. 3pF
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LTC2220-1
+
CM
+ -
3pF
-
25
Figure 4. Differential Drive with an Amplifier
VCM 1k 0.1F ANALOG INPUT 1k 25 2.2F AIN+ AIN+ 12pF 25 0.1F AIN- AIN-
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LTC2220-1
Figure 5. Single-Ended Drive
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The AIN+ and AIN- inputs each have two pins to reduce package inductance. The two AIN+ and the two AIN- pins should be shorted together. For input frequencies above 100MHz the input circuits of Figure 6, 7 and 8 are recommended. The balun transformer gives better high frequency response than a flux coupled center tapped transformer. The coupling capacitors allow the analog inputs to be DC biased at 1.6V. In Figure 8 the series inductors are impedance matching elements that maximize the ADC bandwidth.
VCM 2.2F 0.1F ANALOG INPUT 25 T1 0.1F 25 12 12 0.1F AIN+ AIN+ 8pF AIN- AIN- T1 = MA/COM ETC1-1-13 RESISTORS, CAPACITORS ARE 0402 PACKAGE SIZE
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LTC2220-1
Figure 6. Recommended Front End Circuit for Input Frequencies Between 100MHz and 250MHz
VCM 2.2F 0.1F ANALOG INPUT 25 T1 0.1F 25 AIN- AIN- T1 = MA/COM ETC1-1-13 RESISTORS, CAPACITORS ARE 0402 PACKAGE SIZE
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AIN+ 0.1F AIN+
LTC2220-1
Figure 7. Recommended Front End Circuit for Input Frequencies Between 250MHz and 500MHz
VCM 2.2F 0.1F ANALOG INPUT 25 T1 0.1F 25 4.7nH 4.7nH 0.1F AIN+ AIN+ 2pF AIN- AIN- T1 = MA/COM ETC1-1-13 RESISTORS, CAPACITORS ARE 0402 PACKAGE SIZE
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LTC2220-1
Figure 8. Recommended Front End Circuit for Input Frequencies Above 500MHz
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Reference Operation Figure 9 shows the LTC2220-1 reference circuitry consisting of a 1.6V bandgap reference, a difference amplifier and switching and control circuit. The internal voltage reference can be configured for two pin selectable input ranges of 2V (1V differential) or 1V (0.5V differential). Tying the SENSE pin to VDD selects the 2V range; typing the SENSE pin to VCM selects the 1V range. The 1.6V bandgap reference serves two functions: its output provides a DC bias point for setting the common mode voltage of any external input circuitry; additionally, the reference is used with a difference amplifier to generate the differential reference levels needed by the internal ADC circuitry. An external bypass capacitor is required for the 1.6V reference output, VCM. This provides a high frequency low impedance path to ground for internal and external circuitry. The difference amplifier generates the high and low reference for the ADC. High speed switching circuits are connected to these outputs and they must be externally bypassed. Each output has four pins: two each of REFHA and REFHB for the high reference and two each of REFLA and REFLB for the low reference. The multiple output pins are needed to reduce package inductance. Bypass capacitors must be connected as shown in Figure 9.
LTC2220-1 1.6V VCM 2.2F 1V RANGE DETECT AND CONTROL SENSE REFLB 0.1F REFHA BUFFER INTERNAL ADC HIGH REFERENCE 0.5V 4 1.6V BANDGAP REFERENCE TIE TO VDD FOR 2V RANGE; TIE TO VCM FOR 1V RANGE; RANGE = 2 * VSENSE FOR 0.5V < VSENSE < 1V 1F 2.2F DIFF AMP 1F REFLA 0.1F REFHB INTERNAL ADC LOW REFERENCE
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Figure 9. Equivalent Reference Circuit
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Other voltage ranges in between the pin selectable ranges can be programmed with two external resistors as shown in Figure 10. An external reference can be used by applying its output directly or through a resistor divider to SENSE. It is not recommended to drive the SENSE pin with a logic device. The SENSE pin should be tied to the appropriate level as close to the converter as possible. If the SENSE pin is driven externally, it should be bypassed to ground as close to the device as possible with a 1F ceramic capacitor.
1.6V VCM
2.2F 12k 0.8V 12k SENSE 1F LTC2220-1
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Figure 10. 1.6V Range ADC
Input Range The input range can be set based on the application. The 2V input range will provide the best signal-to-noise performance while maintaining excellent SFDR. The 1V input range will have better SFDR performance, but the SNR will degrade by 5dB. See the Typical Performance Characteristics section. Driving the Encode Inputs The noise performance of the LTC2220-1 can depend on the encode signal quality as much as on the analog input. The ENC+/ENC- inputs are intended to be driven differentially, primarily for noise immunity from common mode noise sources. Each input is biased through a 6k resistor to a 1.6V bias. The bias resistors set the DC operating point for transformer coupled drive circuits and can set the logic threshold for single-ended drive circuits. Any noise present on the encode signal will result in additional aperture jitter that will be RMS summed with the inherent ADC aperture jitter. In applications where jitter is critical (high input frequencies) take the following into consideration: 1. Differential drive should be used.
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2. Use as large an amplitude as possible; if transformer coupled use a higher turns ratio to increase the amplitude. 3. If the ADC is clocked with a sinusoidal signal, filter the encode signal to reduce wideband noise. 4. Balance the capacitance and series resistance at both encode inputs so that any coupled noise will appear at both inputs as common mode noise. The encode inputs have a common mode range of 1.1V to 2.5V. Each input may be driven from ground to VDD for single-ended drive.
LTC2220-1 VDD TO INTERNAL ADC CIRCUITS 1.6V BIAS 6k ENC+ 0.1F CLOCK INPUT 50 1:4 VDD 1.6V BIAS 6k ENC- VDD
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Figure 11. Transformer Driven ENC+/ENC-
Maximum and Minimum Encode Rates The maximum encode rate for the LTC2220-1 is 185Msps. For the ADC to operate properly, the encode signal should have a 50% (5%) duty cycle. Each half cycle must have at least 2.5ns for the ADC internal circuitry to have enough settling time for proper operation. Achieving a precise 50% duty cycle is easy with differential sinusoidal drive using a transformer or using symmetric differential logic such as PECL or LVDS. An optional clock duty cycle stabilizer circuit can be used if the input clock has a non 50% duty cycle. This circuit uses the rising edge of the ENC+ pin to sample the analog input. The falling edge of ENC+ is ignored and the internal falling edge is generated by a phase-locked loop. The input clock duty cycle can vary from 30% to 70% and the clock duty cycle stabilizer will maintain a constant 50% internal
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duty cycle. If the clock is turned off for a long period of time, the duty cycle stabilizer circuit will require one hundred clock cycles for the PLL to lock onto the input clock. To use the clock duty cycle stabilizer, the MODE pin should be connected to 1/3VDD or 2/3VDD using external resistors. The lower limit of the LTC2220-1 sample rate is determined by droop of the sample-and-hold circuits. The pipelined architecture of this ADC relies on storing analog signals on small valued capacitors. Junction leakage will discharge the capacitors. The specified minimum operating frequency for the LTC2220-1 is 1Msps.
VTHRESHOLD = 1.6V ENC+ 1.6V ENC- 0.1F
LTC2220-1
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Figure 12a. Single-Ended ENC Drive, Not Recommended for Low Jitter
3.3V MC100LVELT22 3.3V 130 Q0 130 ENC
+
D0
Q0 83
ENC- 83
LTC2220-1
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Figure 12b. ENC Drive Using a CMOS to PECL Translator
DIGITAL OUTPUTS
Table 1. Output Codes vs Input Voltage
AIN+ - AIN- (2V Range) >+1.000000V +0.999512V +0.999024V +0.000488V 0.000000V -0.000488V -0.000976V -0.999512V -1.000000V <-1.000000V OF 1 0 0 0 0 0 0 0 0 1 D11 - D0 (Offset Binary) 1111 1111 1111 1111 1111 1111 1111 1111 1110 1000 0000 0001 1000 0000 0000 0111 1111 1111 0111 1111 1110 0000 0000 0001 0000 0000 0000 0000 0000 0000 D11 - D0 (2's Complement) 0111 1111 1111 0111 1111 1111 0111 1111 1110 0000 0000 0001 0000 0000 0000 1111 1111 1111 1111 1111 1110 1000 0000 0001 1000 0000 0000 1000 0000 0000
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Digital Output Modes The LTC2220-1 can operate in several digital output modes: LVDS, CMOS running at full speed, and CMOS demultiplexed onto two buses, each of which runs at half speed. In the demultiplexed CMOS modes the two buses (referred to as bus A and bus B) can either be updated on alternate clock cycles (interleaved mode) or simultaneously (simultaneous mode). For details on the clock timing, refer to the timing diagrams. The LVDS pin selects which digital output mode the part uses. This pin has a four-level logic input which should be connected to GND, 1/3VDD, 2/3VDD or VDD. An external resistor divider can be used to set the 1/3VDD or 2/3VDD logic values. Table 2 shows the logic states for the LVDS pin.
Table 2. LVDS Pin Function
LVDS GND 1/3VDD 2/3VDD VDD Digital Output Mode Full-Rate CMOS Demultiplexed CMOS, Simultaneous Update Demultiplexed CMOS, Interleaved Update LVDS
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Digital Output Buffers (CMOS Modes) Figure 13a shows an equivalent circuit for a single output buffer in the CMOS output mode. Each buffer is powered by OVDD and OGND, which are isolated from the ADC power and ground. The additional N-channel transistor in the output driver allows operation down to voltages as low as 0.5V. The internal resistor in series with the output makes the output appear as 50 to external circuitry and may eliminate the need for external damping resistors.
LTC2220-1 OVDD VDD VDD 0.5V TO 3.6V 0.1F OVDD DATA FROM LATCH OE OGND PREDRIVER LOGIC 43 TYPICAL DATA OUTPUT
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Figure 13a. Digital Output Buffer in CMOS Mode
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As with all high speed/high resolution converters, the digital output loading can affect the performance. The digital outputs of the LTC2220-1 should drive a minimal capacitive load to avoid possible interaction between the digital outputs and sensitive input circuitry. The output should be buffered with a device such as an ALVCH16373 CMOS latch. For full speed operation the capacitive load should be kept under 10pF. Lower OVDD voltages will also help reduce interference from the digital outputs. Digital Output Buffers (LVDS Mode) Figure 13b shows an equivalent circuit for a differential output pair in the LVDS output mode. A 3.5mA current is steered from OUT+ to OUT- or vice versa which creates a 350mV differential voltage across the 100 termination resistor at the LVDS receiver. A feedback loop regulates the common mode output voltage to 1.25V. For proper operation each LVDS output pair needs an external 100 termination resistor, even if the signal is not used (such as OF+/OF- or CLKOUT+/CLKOUT-). To minimize noise the PC board traces for each LVDS output pair should be routed close together. To minimize clock skew all LVDS PC board traces should have about the same length.
LTC2220-1
OVDD
D
D
- +
1.25V D
OUT+
10k
10k
100 OUT-
D
LVDS RECEIVER
3.5mA
OGND
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Figure 13b. Digital Output in LVDS Mode
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Data Format The LTC2220-1 parallel digital output can be selected for offset binary or 2's complement format. The format is selected with the MODE pin. Connecting MODE to GND or 1/3VDD selects offset binary output format. Connecting MODE to 2/3VDD or VDD selects 2's complement output format. An external resistor divider can be used to set the 1/3VDD or 2/3VDD logic values. Table 3 shows the logic states for the MODE pin.
Table 3. MODE Pin Function
MODE Pin 0 1/3VDD 2/3VDD VDD Output Format Offset Binary Offset Binary 2's Complement 2's Complement Clock Duty Cycle Stablizer Off On On Off
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Overflow Bit An overflow output bit indicates when the converter is overranged or underranged. In CMOS mode, a logic high on the OFA pin indicates an overflow or underflow on the A data bus, while a logic high on the OFB pin indicates an overflow or underflow on the B data bus. In LVDS mode, a differential logic high on the OF+/OF- pins indicates an overflow or underflow. Output Clock The ADC has a delayed version of the ENC+ input available as a digital output, CLKOUT. The CLKOUT pin can be used to synchronize the converter data to the digital system. This is necessary when using a sinusoidal encode. In all CMOS modes, A bus data will be updated just after CLKOUTA rises and can be latched on the falling edge of CLKOUTA. In demux CMOS mode with interleaved update, B bus data will be updated just after CLKOUTB rises and can be latched on the falling edge of CLKOUTB. In demux CMOS mode with simultaneous update, B bus data will be updated just after CLKOUTB falls and can be latched on the rising edge of CLKOUTB. In LVDS mode, data will be updated just after CLKOUT+/CLKOUT- rises and can be latched on the falling edge of CLKOUT+/CLKOUT-.
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Output Driver Power
Separate output power and ground pins allow the output drivers to be isolated from the analog circuitry. The power supply for the digital output buffers, OVDD, should be tied to the same power supply as for the logic being driven. For example if the converter is driving a DSP powered by a 1.8V supply then OVDD should be tied to that same 1.8V supply. In the CMOS output mode, OVDD can be powered with any voltage up to 3.6V. OGND can be powered with any voltage from GND up to 1V and must be less than OVDD. The logic outputs will swing between OGND and OVDD. In the LVDS output mode, OVDD should be connected to a 3.3V supply and OGND should be connected to GND. Output Enable The outputs may be disabled with the output enable pin, OE. In CMOS or LVDS output modes OE high disables all data outputs including OF and CLKOUT. The data access and bus relinquish times are too slow to allow the outputs to be enabled and disabled during full speed operation. The output Hi-Z state is intended for use during long periods of inactivity. The Hi-Z state is not a truly open circuit; the output pins that make an LVDS output pair have a 20k resistance between them. Therefore in the CMOS output mode, adjacent data bits will have 20k resistance in between them, even in the Hi-Z state. Sleep and Nap Modes The converter may be placed in shutdown or nap modes to conserve power. Connecting SHDN to GND results in normal operation. Connecting SHDN to VDD and OE to VDD results in sleep mode, which powers down all circuitry including the reference and typically dissipates 1mW. When exiting sleep mode it will take milliseconds for the output data to become valid because the reference capacitors have to recharge and stabilize. Connecting SHDN to VDD and OE to GND results in nap mode, which typically dissipates
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35mW. In nap mode, the on-chip reference circuit is kept on, so that recovery from nap mode is faster than that from sleep mode, typically taking 100 clock cycles. In both sleep and nap mode all digital outputs are disabled and enter the Hi-Z state. GROUNDING AND BYPASSING The LTC2220-1 requires a printed circuit board with a clean unbroken ground plane. A multilayer board with an internal ground plane is recommended. Layout for the printed circuit board should ensure that digital and analog signal lines are separated as much as possible. In particular, care should be taken not to run any digital signal alongside an analog signal or underneath the ADC. High quality ceramic bypass capacitors should be used at the VDD, OVDD, VCM, REFHA, REFHB, REFLA and REFLB pins as shown in the block diagram on the front page of this data sheet. Bypass capacitors must be located as close to the pins as possible. Of particular importance are the capacitors between REFHA and REFLB and between REFHB and REFLA. These capacitors should be as close to the device as possible (1.5mm or less). Size 0402 ceramic capacitors are recommended. The 2.2F capacitor between REFHA and REFLA can be somewhat further away. The traces connecting the pins and bypass capacitors must be kept short and should be made as wide as possible. The LTC2220-1 differential inputs should run parallel and close to each other. The input traces should be as short as possible to minimize capacitance and to minimize noise pickup. HEAT TRANSFER Most of the heat generated by the LTC2220-1 is transferred from the die through the bottom-side exposed pad and package leads onto the printed circuit board. For good electrical and thermal performance, the exposed pad should be soldered to a large grounded pad on the PC board. It is critical that all ground pins are connected to a ground plane of sufficient area.
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Clock Sources for Undersampling
Undersampling raises the bar on the clock source and the higher the input frequency, the greater the sensitivity to clock jitter or phase noise. A clock source that degrades SNR of a full-scale signal by 1dB at 70MHz will degrade SNR by 3dB at 140MHz, and 4.5dB at 190MHz. In cases where absolute clock frequency accuracy is relatively unimportant and only a single ADC is required, a 3V canned oscillator from vendors such as Saronix or Vectron can be placed close to the ADC and simply connected directly to the ADC. If there is any distance to the ADC, some source termination to reduce ringing that may occur even over a fraction of an inch is advisable. You must not allow the clock to overshoot the supplies or performance will suffer. Do not filter the clock signal with a narrow band filter unless you have a sinusoidal clock source, as the rise and fall time artifacts present in typical digital clock signals will be translated into phase noise. The lowest phase noise oscillators have single-ended sinusoidal outputs, and for these devices the use of a filter close to the ADC may be beneficial. This filter should be close to the ADC to both reduce roundtrip reflection times, as well as reduce the susceptibility of the traces between the filter and the ADC. If you are sensitive to close-in phase noise, the power supply for oscillators and any buffers
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must be very stable, or propagation delay variation with supply will translate into phase noise. Even though these clock sources may be regarded as digital devices, do not operate them on a digital supply. If your clock is also used to drive digital devices such as an FPGA, you should locate the oscillator, and any clock fan-out devices close to the ADC, and give the routing to the ADC precedence. The clock signals to the FPGA should have series termination at the source to prevent high frequency noise from the FPGA disturbing the substrate of the clock fan-out device. If you use an FPGA as a programmable divider, you must re-time the signal using the original oscillator, and the retiming flip-flop as well as the oscillator should be close to the ADC, and powered with a very quiet supply. For cases where there are multiple ADCs, or where the clock source originates some distance away, differential clock distribution is advisable. This is advisable both from the perspective of EMI, but also to avoid receiving noise from digital sources both radiated, as well as propagated in the waveguides that exist between the layers of multilayer PCBs. The differential pairs must be close together, and distanced from other signals. The differential pair should be guarded on both sides with copper distanced at least 3x the distance between the traces, and grounded with vias no more than 1/4 inch apart.
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U1 FINII08 R1 100
U3
AIN+ R13 100 R14 100 R15 100 R16 100 VCC R17 100 R18 100 R19 100
C7 12pF
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 GND GND EN/12 RIN1- RIN1+ RIN2+ RIN2- RIN3- RIN3+ RIN4+ RIN4- VCC EN RIN5- RIN5+ RIN6+ RIN6- RIN7- RIN7+ RIN8+ RIN8- EN/34 GND VBB VCC VCC EN/78 DOUT1- DOUT1+ DOUT2+ DOUT2- DOUT3- DOUT3+ DOUT4+ DOUT4- GND GND DOUT5- DOUT5+ DOUT6+ DOUT6- DOUT7- DOUT7+ DOUT8+ DOUT8- EN/56 VCC VCC VCC U2 FINII08 48 47 46 45 44 43 42 41 40 39 38 37 36 35 34 33 32 31 30 29 28 27 26 25
R20 100 R21 100 R23 100 R24 100 R25 100
1 2 3 4 AIN- 5 6 C16 C17 0.1F 7 1F 8 C19 2.2F 9 10 C18 C11 VDD 1F 0.1F 11 12 C21 62 0.1F 63 13 VDD 14 15 C24 VDD JP3 0.1F 17 CLK 18 GND SHDN CLK 19 20 25 C29 33 2.2F VDD GND 41 VDD 50 0E JP1 60 VCM JP20 SENSE 59 VDD 16 VCM 61 VCM 64 EXT 58 REF 57 C35 VDD 0.1F
LTC2220-1 AIN+ OF+/OFA + AIN OF-/DA11 AIN- D11+/DA10 AIN- D11-/DA9 REFHA D10+/DA8 REFHA D10-/DA7 REFLB D9+/DA6 REFLB D9-/DA5 REFHB D8+/DA4 REFHB D8-/DA3 REFLA D7+/DA2 REFLA D7-/DA1 VDD D6+/DA0 VDD D6-/CLKOUTA VDD D5+/CLKOUTB VDD DB5-/OFB VDD CLKOUT+/DB11 ENC+ CLKOUT-/DB10 ENC- D4+/DB9 SHDN D4-/DB8 OEL D3+/DB7 OGND D3-/DB6 OGND D2+/DB5 OGND D2-/DB4 OGND D1+/DB3 VCM D1-/DB2 SENSE D0+/DB1 GND D0-/DB0 GND OVDD GND OVDD MODE OVDD LVDS OVDD 56 55 54 53 52 51 48 47 46 45 44 43 40 39 38 37 36 35 32 31 30 29 28 27 24 23 22 21 49 42 34 26
JP7 VCC R26 100 ENABLE
VDD C33 0.1F PWR GND GND U4 24LCO25 C31 0.1F VDD VDD C30 0.1F R11 24.9 AIN J6 ENCODE INPUT R7 100 AIN R12 24.9 * FOR AIN > 100MHz, REPLACE T1 WITH A ETC1-1-13
- +
C34 4.7F
R28 1k 2/3VDD C4 0.1F R2 4.99k 1% R3 4.99k 1% SCL VSS VCC_IN
MODE C32 0.1F
VSS SCL SDA VCC_IN R6 4.7k VCC VCC ENABLE EDGE-CON-100 VDD
R29 1k 1/3VDD R30 1k GND
C39 0.1F
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 GND GND EN/12 RIN1- RIN1+ RIN2+ RIN2- RIN3- RIN3+ RIN4+ RIN4- VCC EN RIN5- RIN5+ RIN6+ RIN6- RIN7- RIN7+ RIN8+ RIN8- EN/34 GND VBB VCC VCC EN/78 DOUT1- DOUT1+ DOUT2+ DOUT2- DOUT3- DOUT3+ DOUT4+ DOUT4- GND GND DOUT5- DOUT5+ DOUT6+ DOUT6- DOUT7- DOUT7+ DOUT8+ DOUT8- EN/56 VCC VCC 48 47 46 45 44 43 42 41 40 39 38 37 36 35 34 33 32 31 30 29 28 27 26 25
2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50 52 54 56 58 60 62 64 66 68 70 72 74 76 78 80 82 84 86 88 90 92 94 96 98 100
1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43 45 47 49 51 53 55 57 59 61 63 65 67 69 71 73 75 77 79 81 83 85 87 89 91 93 95 97 99
VDD 3.3V C3 4.7F JP4
1 A0 2 A1 3 A2 4 A3 8 VCC 7 WP 6 SCL 5 SDA
R4 4.99k 1% SDA
L1 VCC MURATA BLM18BB470SN C5 4.7F CLK R8 100 C25 33pF CLK C20 0.1F OPT VCC VCC 3.3V
J9
C27 0.1F C26 0.1F
ANALOG INPUT
T1* ETC1-1T
R9 24.9
T2 ETC1-1T
R10 24.9
C1 0.1F
C2 0.1F
C5 0.1F
C6 0.1F
C8 0.1F
C9 0.1F
C10 0.1F
C12 0.1F
C36 4.7F
C23 0.1F
VCM
LTC2220-1
23
R27 50
C22 0.1F
U
APPLICATIO S I FOR ATIO W UU
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LTC2220-1
APPLICATIO S I FOR ATIO U
Silkscreen Top
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LTC2220-1
APPLICATIO S I FOR ATIO U
Layer 1 Component Side
Layer 2 GND Plane
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25
LTC2220-1
APPLICATIO S I FOR ATIO U
Layer 3 Power Plane
Layer 4 Bottom Side
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LTC2220-1
PACKAGE DESCRIPTIO
0.25 0.05 0.50 BSC RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS 9 .00 0.10 (4 SIDES) 0.75 0.05 R = 0.115 TYP
PIN 1 TOP MARK (SEE NOTE 5)
0.00 - 0.05 NOTE: 1. DRAWING CONFORMS TO JEDEC PACKAGE OUTLINE MO-220 VARIATION WNJR-5 2. ALL DIMENSIONS ARE IN MILLIMETERS 3. DIMENSIONS OF EXPOSED PAD ON BOTTOM OF PACKAGE DO NOT INCLUDE MOLD FLASH. MOLD FLASH, IF PRESENT, SHALL NOT EXCEED 0.20mm ON ANY SIDE, IF PRESENT 4. EXPOSED PAD SHALL BE SOLDER PLATED 5. SHADED AREA IS ONLY A REFERENCE FOR PIN 1 LOCATION ON THE TOP AND BOTTOM OF PACKAGE 6. DRAWING NOT TO SCALE
Information furnished by Linear Technology Corporation is believed to be accurate and reliable. However, no responsibility is assumed for its use. Linear Technology Corporation makes no representation that the interconnection of its circuits as described herein will not infringe on existing patent rights.
U
UP Package 64-Lead Plastic QFN (9mm x 9mm)
(Reference LTC DWG # 05-08-1705)
0.70 0.05 7.15 0.05 8.10 0.05 9.50 0.05 (4 SIDES) PACKAGE OUTLINE 63 64 0.40 0.10 1 2 PIN 1 CHAMFER 7.15 0.10 (4-SIDES) 0.200 REF 0.25 0.05 0.50 BSC BOTTOM VIEW--EXPOSED PAD
(UP64) QFN 1003
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LTC2220-1
RELATED PARTS
PART NUMBER LTC1748 LTC1750 LT1993-2 LT(R)1994 LTC2202 LTC2208 LTC2220 LTC2220-1 LTC2221 LTC2224 LTC2230 LTC2231 LTC2255 LTC2284 LT5512 LT5514 LT5515 LT5516 LT5517 LT5522 DESCRIPTION 14-Bit, 80Msps, 5V ADC 14-Bit, 80Msps, 5V Wideband ADC High Speed Differential Op Amp Low Noise, Low Distortion Fully Differential Input/ Output Amplifier/Driver 16-Bit, 10Msps, 3.3V ADC, Lowest Noise 16-Bit, 130Msps, 3.3V ADC, LVDS Outputs 12-Bit, 170Msps, 3.3V ADC, LVDS Outputs 12-Bit, 185Msps, 3.3V ADC, LVDS Outputs 12-Bit, 135Msps, 3.3V ADC, LVDS Outputs 12-Bit, 135Msps, 3.3V ADC, High IF Sampling 10-Bit, 170Msps, 3.3V ADC, LVDS Outputs 10-Bit, 135Msps, 3.3V ADC, LVDS Outputs 14-Bit, 125Msps, 3V ADC, Lowest Power 14-Bit, Dual, 105Msps, 3V ADC, Low Crosstalk DC-3GHz High Signal Level Downconverting Mixer Ultralow Distortion IF Amplifier/ADC Driver with Digitally Controlled Gain 1.5GHz to 2.5GHz Direct Conversion Quadrature Demodulator COMMENTS 76.3dB SNR, 90dB SFDR, 48-Pin TSSOP Package Up to 500MHz IF Undersampling, 90dB SFDR 800MHz BW, 70dBc Distortion at 70MHz, 6dB Gain Low Distortion: -94dBc at 1MHz 150mW, 81.6dB SNR, 100dB SFDR, 48-pin QFN 1250mW, 78dB SNR, 100dB SFDR, 64-pin QFN 890mW, 67.7dB SNR, 84dB SFDR, 64-pin QFN 910mW, 67.7dB SNR, 80dB SFDR, 64-pin QFN 660mW, 67.8dB SNR, 84dB SFDR, 64-pin QFN 630mW, 67.6dB SNR, 84dB SFDR, 48-pin QFN 890mW, 61.2dB SNR, 78dB SFDR, 64-pin QFN 660mW, 61.2dB SNR, 78dB SFDR, 64-pin QFN 395mW, 72.5dB SNR, 88dB SFDR, 32-pin QFN 540mW, 72.4dB SNR, 88dB SFDR, 64-pin QFN DC to 3GHz, 21dBm IIP3, Integrated LO Buffer 450MHz to 1dB BW, 47dB OIP3, Digital Gain Control 10.5dB to 33dB in 1.5dB/Step High IIP3: 20dBm at 1.9GHz, Integrated LO Quadrature Generator
800MHz to 1.5GHz Direct Conversion Quadrature Demodulator High IIP3: 21.5dBm at 900MHz, Integrated LO Quadrature Generator 40MHz to 900MHz Direct Conversion Quadrature Demodulator High IIP3: 21dBm at 800MHz, Integrated LO Quadrature Generator 600MHz to 2.7GHz High Linearity Downconverting Mixer 4.5V to 5.25V Supply, 25dBm IIP3 at 900MHz. NF = 12.5dB, 50 Single Ended RF and LO Ports
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Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900 FAX: (408) 434-0507
LT 0106 REV A * PRINTED IN USA
www.linear.com
(c) LINEAR TECHNOLOGY CORPORATION 2005

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