19-4630; Rev 0; 7/09 KIT ATION EVALU LE B A IL A AV Octal, 12-Bit, 64Msps, 1.8V ADC with Serial LVDS Outputs The MAX1438B octal, 12-bit analog-to-digital converter (ADC) features fully differential inputs, a pipelined architecture, and digital error correction incorporating a fully differential signal path. This ADC is optimized for low-power and high-dynamic performance in medical imaging instrumentation and digital communications applications. The MAX1438B operates from a 1.8V single supply and consumes only 913mW (114mW per channel) while delivering a 69.9dB (typ) signal-to-noise ratio (SNR) at a 5.3MHz input frequency. In addition to low operating power, the MAX1438B features a lowpower standby mode for idle periods. An internal 1.24V precision bandgap reference sets the full-scale range of the ADC. A flexible reference structure allows the use of an external reference for applications requiring increased accuracy or a different input voltage range. The reference architecture is optimized for low noise. A single-ended clock controls the data-conversion process. An internal duty-cycle equalizer compensates for wide variations in clock duty cycle. An on-chip phase-locked loop (PLL) generates the high-speed serial low-voltage differential signal (LVDS) clock. The MAX1438B has self-aligned serial LVDS outputs for data, clock, and frame-alignment signals. The output data is presented in two’s-complement format. The MAX1438B offers a maximum sample rate of 64Msps. This device is available in a small, 10mm x 10mm x 0.8mm, 68-pin thin QFN package with exposed pad and is specified for the extended industrial (-40°C to +85°C) temperature range. Applications Features ♦ Excellent Dynamic Performance 69.9dB SNR at 5.3MHz 94dBc SFDR at 5.3MHz ♦ Ultra-Low Power 114mW per Channel (Normal Operation) ♦ Serial LVDS Outputs ♦ Pin-Selectable LVDS/SLVS (Scalable Low-Voltage Signal) Mode ♦ LVDS Outputs Support Up to 30in FR4 Backplane Connections ♦ Test Mode for Digital Signal Integrity ♦ Fully Differential Analog Inputs ♦ Wide Differential Input Voltage Range (1.4VP-P) ♦ On-Chip 1.24V Precision Bandgap Reference ♦ Clock Duty-Cycle Equalizer ♦ Compact, 68-Pin Thin QFN Package with Exposed Pad ♦ Evaluation Kit Available (Order MAX1437BEVKIT) Ordering Information PART TEMP RANGE PIN-PACKAGE MAX1438BETK+ -40°C to +85°C 68 Thin QFN-EP* +Denotes a lead(Pb)-free/RoHS-compliant package. *EP = Exposed pad. Ultrasound and Medical Imaging Instrumentation Multichannel Communications Pin Configuration appears at end of data sheet. ________________________________________________________________ Maxim Integrated Products For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com. 1 MAX1438B General Description MAX1438B Octal, 12-Bit, 64Msps, 1.8V ADC with Serial LVDS Outputs ABSOLUTE MAXIMUM RATINGS AVDD to GND........................................................-0.3V to +2.0V CVDD to GND........................................................-0.3V to +3.6V OVDD to GND .......................................................-0.3V to +2.0V IN_P, IN_N to GND .................................-0.3V to (VAVDD + 0.3V) CLK to GND ...........................................-0.3V to (VCVDD + 0.3V) OUT_P, OUT_N, FRAME_, CLKOUT_ to GND ..............................-0.3V to (VOVDD + 0.3V) DT, SLVS/LVDS, LVDSTEST, PLL_, STBY REFIO, REFADJ, CMOUT to GND......-0.3V to (VAVDD + 0.3V) Continuous Power Dissipation (TA = +70°C) 68-Pin Thin QFN, 10mm x 10mm x 0.8mm (derate 70mW/°C above +70°C) ................................4000mW Operating Temperature Range ...........................-40°C to +85°C Maximum Junction Temperature .....................................+150°C Storage Temperature Range .............................-65°C to +150°C Lead Temperature (soldering, 10s) .................................+300°C Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability. ELECTRICAL CHARACTERISTICS (VAVDD = 1.8V, VOVDD = 1.8V, VCVDD = 1.8V, VGND = 0V, external VREFIO = 1.24V, CREFIO to GND = 0.1µF || 1.0µF, CREFP to GND = 10µF, CREFN to GND = 10µF, fCLK = 64MHz (50% duty cycle), DT = 0, TA = TMIN to TMAX, unless otherwise noted. Typical values are at TA = +25°C.) (Note 1) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS DC ACCURACY (Note 2) Resolution N Integral Nonlinearity INL Differential Nonlinearity DNL 12 No missing codes over temperature Bits ±0.4 ±2.5 LSB ±0.25 ±1 LSB ±0.5 %FS +2 %FS Offset Error Gain Error -3 ±0.5 ANALOG INPUTS (IN_P, IN_N) Input Differential Range Common-Mode Voltage Range VID Differential input VCMO Common-Mode Voltage Range Tolerance (Note 3) Differential Input Impedance RIN Differential Input Capacitance CIN Switched capacitor load 1.4 VP-P 0.76 V ±50 mV 2 kΩ 12.5 pF 4.0 MHz 6.5 Cycles CONVERSION RATE Maximum Conversion Rate fSMAX Minimum Conversion Rate fSMIN 64 Data Latency MHz DYNAMIC CHARACTERISTICS (Differential Inputs, 4096-Point FFT) (Note 2) Signal-to-Noise Ratio SNR Signal-to-Noise and Distortion SINAD Effective Number of Bits ENOB Spurious-Free Dynamic Range SFDR 2 fIN = 5.3MHz at -0.5dBFS fIN = 20MHz at -0.5dBFS 69.9 67 69.6 67 69.6 fIN = 5.3MHz at -0.5dBFS fIN = 20MHz at -0.5dBFS 69.8 fIN = 5.3MHz at -0.5dBFS fIN = 20MHz at -0.5dBFS 11.4 10.8 11.4 79 93 fIN = 5.3MHz at -0.5dBFS fIN = 20MHz at -0.5dBFS 94 _______________________________________________________________________________________ dB dB Bits dBc Octal, 12-Bit, 64Msps, 1.8V ADC with Serial LVDS Outputs (VAVDD = 1.8V, VOVDD = 1.8V, VCVDD = 1.8V, VGND = 0V , external VREFIO = 1.24V, CREFIO to GND = 0.1µF || 1.0µF, CREFP to GND = 10µF, CREFN to GND = 10µF, fCLK = 64MHz (50% duty cycle), DT = 0, TA = TMIN to TMAX, unless otherwise noted. Typical values are at TA = +25°C.) (Note 1) PARAMETER SYMBOL CONDITIONS MIN TYP fIN = 5.3MHz at -0.5dBFS -95 fIN = 20MHz at -0.5dBFS -92 MAX UNITS Total Harmonic Distortion THD Intermodulation Distortion IMD f1 = 5.3MHz at -6.5dBFS f2 = 6.3MHz at -6.5dBFS 89.3 dBc Third-Order Intermodulation IM3 f1 = 5.3MHz at -6.5dBFS f2 = 6.3MHz at -6.5dBFS 97.5 dBc Aperture Jitter tAJ Figure 10 < 0.4 psRMS Aperture Delay tAD Figure 10 1 ns -79 dBc Small-Signal Bandwidth SSBW Input at -20dBFS 100 MHz Full-Power Bandwidth LSBW Input at -0.5dBFS 100 MHz IN_P = IN_N 0.44 LSBRMS 1 Clock cycle Output Noise Overrange Recovery Time tOR RS = 25Ω, CS = 50pF INTERNAL REFERENCE REFADJ Internal Reference-Mode Enable Voltage (Note 4) 0.1 REFADJ Low-Leakage Current REFIO Output Voltage Reference Temperature Coefficient 1.5 VREFIO 1.18 TCREFIO 1.24 V mA 1.30 120 V ppm/°C EXTERNAL REFERENCE REFADJ External ReferenceMode Enable Voltage (Note 4) VAVDD 0.1V V REFADJ High-Leakage Current 200 µA REFIO Input Voltage 1.24 V REFIO Input Voltage Tolerance REFIO Input Current IREFIO ±5 % <1 µA 0.76 V COMMON-MODE OUTPUT (CMOUT) CMOUT Output Voltage VCMOUT CLOCK INPUT (CLK) Input High Voltage VCLKH Input Low Voltage VCLKL 0.8 x VAVDD V 0.2 x VAVDD Clock Duty Cycle 50 Clock Duty-Cycle Tolerance % ±30 Input Leakage DIIN Input Capacitance DCIN % Input at GND 5 Input at VAVDD 80 5 V µA pF _______________________________________________________________________________________ 3 MAX1438B ELECTRICAL CHARACTERISTICS (continued) MAX1438B Octal, 12-Bit, 64Msps, 1.8V ADC with Serial LVDS Outputs ELECTRICAL CHARACTERISTICS (continued) (VAVDD = 1.8V, VOVDD = 1.8V, VCVDD = 1.8V, VGND = 0V, external VREFIO = 1.24V, CREFIO to GND = 0.1µF || 1.0µF, CREFP to GND = 10µF, CREFN to GND = 10µF, fCLK = 64MHz (50% duty cycle), DT = 0, TA = TMIN to TMAX, unless otherwise noted. Typical values are at TA = +25°C.) (Note 1) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS DIGITAL INPUTS (PLL_, LVDSTEST, DT, SLVS, STBY) Input High Threshold VIH Input Low Threshold VIL Input Leakage DIIN Input Capacitance DCIN 0.8 x VAVDD V 0.2 x VAVDD Input at GND 5 Input at VAVDD 80 5 V µA pF LVDS OUTPUTS (OUT_P, OUT_N), SLVS/LVDS = 0 Differential Output Voltage Output Common-Mode Voltage VOHDIFF RTERM = 100Ω 250 450 VOCM RTERM = 100Ω 1.125 1.375 mV V Rise Time (20% to 80%) tRL RTERM = 100Ω, CLOAD = 5pF 350 ps Fall Time (80% to 20%) tFL RTERM = 100Ω, CLOAD = 5pF 350 ps SLVS OUTPUTS (OUT_P, OUT_N, CLKOUTP, CLKOUTN, FRAMEP, FRAMEN), SLVS/LVDS = 1, DT = 1 Differential Output Voltage Output Common-Mode Voltage VOHDIFF RTERM = 100Ω VOCM 205 mV RTERM = 100Ω 220 mV Rise Time (20% to 80%) tRS RTERM = 100Ω, CLOAD = 5pF 320 ps Fall Time (80% to 20%) tFS RTERM = 100Ω, CLOAD = 5pF 320 ps STANDBY MODE (STBY) STBY Fall to Output Enable tENABLE 200 µs STBY Rise to Output Disable tDISABLE 60 ns POWER REQUIREMENTS AVDD Supply Voltage Range VAVDD 1.7 1.8 1.9 V OVDD Supply Voltage Range VOVDD 1.7 1.8 1.9 V CVDD Supply Voltage Range VCVDD 1.7 1.8 3.5 V STBY = 0, DT = 0 422 465 AVDD Supply Current OVDD Supply Current IAVDD IOVDD fIN = 20MHz at -0.5dBFS fIN = 20MHz at -0.5dBFS 422 37 STBY = 0 85 STBY = 0, DT = 1 85 STBY = 1, no clock input 16 µA 0 mA CVDD Supply Current ICVDD CVDD is used only to bias ESD-protection diodes on CLK input, Figure 2 Power Dissipation PDISS fIN = 20MHz at -0.5dBFS 4 mA STBY = 0, DT = 1 STBY = 1, no clock input 913 _______________________________________________________________________________________ 110 1035 mA mW Octal, 12-Bit, 64Msps, 1.8V ADC with Serial LVDS Outputs (VAVDD = 1.8V, VOVDD = 1.8V, VCVDD = 1.8V, VGND = 0V, external VREFIO = 1.24V, CREFIO to GND = 0.1µF || 1.0µF, CREFP to GND = 10µF, CREFN to GND = 10µF, fCLK = 64MHz (50% duty cycle), DT = 0, TA = TMIN to TMAX, unless otherwise noted. Typical values are at TA = +25°C.) (Note 1) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS TIMING CHARACTERISTICS (Note 5) (tSAMPLE/24) - 0.15 (tSAMPLE/24) + 0.15 ns Data Valid to CLKOUT Rise/Fall tOD Figure 5 (Note 6) CLKOUT Output-Width High tCH Figure 5 tSAMPLE/12 ns CLKOUT Output-Width Low tCL Figure 5 tSAMPLE/12 ns FRAME Rise to CLKOUT Rise tCF Figure 4 (Note 6) (tSAMPLE/24) - 0.15 (tSAMPLE/24) + 0.15 ns Sample CLK Rise to FRAME Rise tSF Figure 4 (Note 6) (tSAMPLE/2) + 1.1 (tSAMPLE/2) + 2.6 ns Crosstalk (Note 2) -73 dB Gain Matching CGM fIN = 5.3MHz (Note 2) ±0.1 dB Phase Matching CPM fIN = 5.3MHz (Note 2) ±0.25 Degrees Note 1: Specifications at TA ≥ +25°C are guaranteed by production testing. Specifications at TA < +25°C are guaranteed by design and characterization and not subject to production testing. Note 2: See definition in the Parameter Definitions section at the end of this data sheet. Note 3: See the Common-Mode Output (CMOUT) section. Note 4: Connect REFADJ to GND directly to enable internal reference mode. Connect REFADJ to AVDD directly to disable the internal bandgap reference and enable external reference mode. Note 5: Data valid to CLKOUT rise/fall timing is measured from 50% of data output level to 50% of clock output level. Note 6: Guaranteed by design and characterization. Not subject to production testing. Typical Operating Characteristics (VAVDD = 1.8V, VOVDD = 1.8V, VCVDD = 1.8V, VGND = 0V, internal reference, differential input at -0.5dBFS, fIN = 5.3MHz, fCLK = 64MHz (50% duty cycle), DT = 0, CLOAD = 10pF, TA = +25°C, unless otherwise noted.) AMPLITUDE (dBFS) -20 -30 -40 -50 -60 -70 -80 HD2 -20 -30 -40 -50 -90 -100 -110 -100 -110 5 10 15 20 FREQUENCY (MHz) 25 30 MEASURED ON CHANNEL 1, WITH INTERFERING SIGNAL ON CHANNEL 2 fIN(N1) = 5.3164063MHz fIN(N2) = 30.3007813MHz CROSSTALK = -72.5dB -30 -70 HD3 -80 HD3 MAX1438B toc03 0 -10 -20 -60 -90 0 fCLK = 64.0000001MHz fIN = 30.3007813MHz AIN = -0.5dBFS SNR = 69.609dB SINAD = 69.585dB THD = -92.323dBc SFDR = -92.870dBc -10 AMPLITUDE (dBFS) fCLK = 64.0000006MHz fIN = 5.3164063MHz AIN = -0.5dBFS SNR = 69.881dB SINAD = 69.874dB THD = -101.811dB SFDR = 100.723dB -10 MAX1438B toc02 0 HD2 AMPLITUDE (dBFS) MAX1438B toc01 0 CROSSTALK (16,384-POINT DATA RECORD) FFT PLOT (16,384-POINT DATA RECORD) FFT PLOT (16,384-POINT DATA RECORD) -40 -50 -60 fIN(N2) -70 -80 -90 -100 -110 0 5 10 15 20 FREQUENCY (MHz) 25 30 0 5 10 15 20 FREQUENCY (MHz) 25 30 _______________________________________________________________________________________ 5 MAX1438B ELECTRICAL CHARACTERISTICS (continued) Typical Operating Characteristics (continued) (VAVDD = 1.8V, VOVDD = 1.8V, VCVDD = 1.8V, VGND = 0V, internal reference, differential input at -0.5dBFS, fIN = 5.3MHz, fCLK = 64MHz (50% duty cycle), DT = 0, CLOAD = 10pF, TA = +25°C, unless otherwise noted.) TWO-TONE INTERMODULATION DISTORTION (16,384-POINT DATA RECORD) -40 -50 -60 -70 -80 -100 0 5 10 15 20 25 30 MAX1438B toc06 MAX1438B toc05 70 SMALL-SIGNAL BANDWIDTH -20.5dBFS -3 -4 -5 -6 69 68 67 66 -9 -10 -110 1 10 65 1000 100 0 20 40 60 80 100 FREQUENCY (MHz) ANALOG INPUT FREQUENCY (MHz) fIN (MHz) SIGNAL-TO-NOISE PLUS DISTORTION vs. ANALOG INPUT FREQUENCY TOTAL HARMONIC DISTORTION vs. ANALOG INPUT FREQUENCY SPURIOUS-FREE DYNAMIC RANGE vs. ANALOG INPUT FREQUENCY -85 MAX1438B toc09 71 120 105 MAX1438B toc08 -80 MAX1438B toc07 72 100 95 70 69 68 SFDR (dBc) -90 THD (dBc) -95 90 85 80 -100 67 75 -105 65 70 65 -110 0 20 40 60 80 100 120 0 20 40 60 80 100 fIN (MHz) SIGNAL-TO-NOISE RATIO vs. ANALOG INPUT POWER SIGNAL-TO-NOISE PLUS DISTORTION vs. ANALOG INPUT POWER 70 fIN = 5.3037109MHz 70 65 60 60 SINAD (dB) 65 55 50 45 45 40 40 35 -25 -20 -15 -10 ANALOG INPUT POWER (dBFS) -5 0 80 100 120 -55 fIN = 5.3037109MHz -60 -65 -75 -80 -85 -90 -95 -100 35 -30 60 -70 55 50 40 TOTAL HARMONIC DISTORTION vs. ANALOG INPUT POWER 75 MAX1438B toc10 fIN = 5.3037109MHz 20 fIN (MHz) fIN (MHz) 75 0 120 MAX1438B toc12 66 THD (dBc) SINAD (dB) 71 -7 -8 -90 6 72 SNR (dB) -30 FULL-POWER BANDWIDTH -0.5dBFS 1 0 -1 -2 MAX1438B toc11 AMPLITUDE (dBFS) -20 2 GAIN (dB) fIN(IN1) = 5.296593MHz fIN(IN2) = 6.299991MHz AIN1 = -6.5dBFS AIN2 = -6.5dBFS IMD = 89.3dBc IM3 = 97.5dBc SIGNAL-TO-NOISE RATIO vs. ANALOG INPUT FREQUENCY BANDWIDTH vs. ANALOG INPUT FREQUENCY MAX1438B toc04 0 -10 SNR (dB) MAX1438B Octal, 12-Bit, 64Msps, 1.8V ADC with Serial LVDS Outputs -105 -30 -25 -20 -15 -10 ANALOG INPUT POWER (dBFS) -5 0 -30 -25 -20 -15 -10 ANALOG INPUT POWER (dBFS) _______________________________________________________________________________________ -5 0 Octal, 12-Bit, 64Msps, 1.8V ADC with Serial LVDS Outputs SIGNAL-TO-NOISE RATIO vs. SAMPLING RATE fIN = 5.3037109MHz 73 SNR (dB) 85 80 72 71 71 70 69 70 68 68 65 67 67 60 66 -25 -20 -15 -10 -5 0 66 10 15 20 25 30 35 40 45 50 55 60 10 15 20 25 30 35 40 45 50 55 60 ANALOG INPUT POWER (dBFS) fCLK (MHz) fCLK (MHz) TOTAL HARMONIC DISTORTION vs. SAMPLING RATE SPURIOUS-FREE DYNAMIC RANGE vs. SAMPLING RATE SIGNAL-TO-NOISE RATIO vs. DUTY CYCLE -85 fIN = 5.3037109MHz 73 110 fIN = 5.3037109MHz 72 105 -95 71 SNR (dB) SFDR (dBc) -90 100 70 -100 95 69 -105 90 68 85 -110 67 10 15 20 25 30 35 40 45 50 55 60 fCLK (MHz) 10 15 20 25 30 35 40 45 50 55 60 fCLK (MHz) MAX1438B toc19 -80 fIN = 5.3037109MHz 72 fIN = 5.3037109MHz -85 -95 -105 85 -110 45 50 55 DUTY CYCLE (%) 60 65 70 65 70 95 68 40 60 100 90 35 55 fIN = 5.3037109MHz -100 30 50 105 69 67 45 110 SFDR (dBc) THD (dBc) 70 40 SPURIOUS-FREE DYNAMIC RANGE vs. DUTY CYCLE -90 71 35 DUTY CYCLE (%) TOTAL HARMONIC DISTORTION vs. DUTY CYCLE SIGNAL-TO-NOISE PLUS DISTORTION vs. DUTY CYCLE 73 30 MAX1438B toc21 fIN = 5.3037109MHz MAX1438B toc18 115 MAX1438B toc16 -80 MAX1438B toc17 -30 SINAD (dB) 70 69 75 THD (dBc) 72 MAX1438B toc20 SFDR (dBc) 90 fIN = 5.3037109MHz 73 SINAD (dB) 95 74 MAX1438B toc14 fIN = 5.3037109MHz 100 74 MAX1438B toc13 105 SIGNAL-TO-NOISE PLUS DISTORTION vs. SAMPLING RATE MAX1438B toc15 SPURIOUS-FREE DYNAMIC RANGE vs. ANALOG INPUT POWER 80 30 35 40 45 50 55 DUTY CYCLE (%) 60 65 70 30 35 40 45 50 55 60 65 70 DUTY CYCLE (%) _______________________________________________________________________________________ 7 MAX1438B Typical Operating Characteristics (continued) (VAVDD = 1.8V, VOVDD = 1.8V, VCVDD = 1.8V, VGND = 0V, internal reference, differential input at -0.5dBFS, fIN = 5.3MHz, fCLK = 64MHz (50% duty cycle), DT = 0, CLOAD = 10pF, TA = +25°C, unless otherwise noted.) Typical Operating Characteristics (continued) (VAVDD = 1.8V, VOVDD = 1.8V, VCVDD = 1.8V, VGND = 0V, internal reference, differential input at -0.5dBFS, fIN = 5.3MHz, fCLK = 64MHz (50% duty cycle), DT = 0, CLOAD = 10pF, TA = +25°C, unless otherwise noted.) fIN = 19.8MHz 4096-POINT DATA RECORD 72 71 71 70 70 fIN = 19.8MHz 4096-POINT DATA RECORD -85 MAX1438B toc24 72 73 MAX1438B toc22 73 TOTAL HARMONIC DISTORTION vs. TEMPERATURE SIGNAL-TO-NOISE PLUS DISTORTION vs. TEMPERATURE MAX1438B toc23 SIGNAL-TO-NOISE RATIO vs. TEMPERATURE fIN = 19.8MHz 4096-POINT DATA RECORD -86 -87 69 68 68 67 66 66 65 65 10 35 60 85 -89 -90 -91 -92 -93 -94 -95 -40 -15 10 35 60 -40 85 -15 10 35 60 TEMPERATURE (°C) TEMPERATURE (°C) TEMPERATURE (°C) SPURIOUS-FREE DYNAMIC RANGE vs. TEMPERATURE SUPPLY CURRENT vs. SAMPLING RATE (AVDD) SUPPLY CURRENT vs. SAMPLING RATE (OVDD) 440 93 90 430 85 MAX1438B toc27 fIN = 19.8MHz 4096-POINT DATA RECORD MAX1438B toc26 85 420 92 IAVDD (mA) 91 90 89 410 IOVDD (mA) 94 -15 MAX1438B toc25 95 SFDR (dBc) 69 67 -40 THD (dBc) SINAD (dB) SNR (dB) -88 400 390 80 75 88 380 87 70 370 86 85 65 360 10 35 60 85 0 5 10 15 20 25 30 35 40 45 50 55 60 0 5 10 15 20 25 30 35 40 45 50 55 60 TEMPERATURE (°C) fCLK (MHz) fCLK (MHz) OFFSET ERROR vs. TEMPERATURE GAIN ERROR vs. TEMPERATURE INTEGRAL NONLINEARITY vs. DIGITAL OUTPUT CODE 0.0 GAIN ERROR (%FS) 0.02 0.01 0.5 MAX1438B toc30 0.2 MAX1438B toc28 0.03 0.4 0.3 0.2 -0.2 INL (LSB) -15 MAX1438B toc29 -40 OFFSET ERROR (%FS) MAX1438B Octal, 12-Bit, 64Msps, 1.8V ADC with Serial LVDS Outputs -0.4 -0.6 0.1 0 -0.1 -0.2 0.00 -0.3 -0.8 -0.4 -40 -15 10 35 TEMPERATURE (˚C) 8 -0.5 -1.0 -0.01 60 85 -40 -15 10 35 TEMPERATURE (NC) 60 85 0 512 1024 1536 2048 2560 3072 3584 4096 DIGITAL OUTPUT CODE _______________________________________________________________________________________ Octal, 12-Bit, 64Msps, 1.8V ADC with Serial LVDS Outputs 0.4 0.3 VAVDD = VOVDD 1.2700 VAVDD = VOVDD 1.2600 VREFIO (V) 0.1 0 -0.1 VREFIO (V) 1.2520 0.2 1.2510 1.2500 -0.2 1.2400 1.2500 -0.3 -0.4 -0.5 1.2300 1.2490 512 1024 1536 2048 2560 3072 3584 4096 1.7 1.8 DIGITAL OUTPUT CODE 1.9 -40 2.1 2.0 -15 10 1.3500 85 0.7810 VAVDD = VOVDD 0.7790 VCMOUT (V) 1.3000 1.2500 MAX1438B toc35 VAVDD = VOVDD 60 CMOUT VOLTAGE vs. SUPPLY VOLTAGE MAX1438B toc34 1.4000 35 TEMPERATURE (NC) SUPPLY VOLTAGE (V) INTERNAL REFERENCE VOLTAGE vs. REFERENCE LOAD CURRENT VREFIO(V) 0.7770 0.7750 1.2000 0.7730 1.1500 0.7710 1.1000 -350 -250 -150 -50 50 150 250 1.7 350 1.8 1.9 2.0 IREFIO (FA) SUPPLY VOLTAGE (V) CMOUT VOLTAGE vs. TEMPERATURE CMOUT VOLTAGE vs. LOAD CURRENT VAVDD = VOVDD 1.0 0.795 2.1 MAX1438B toc37 0.800 MAX1438B toc36 0.9 0.8 0.7 0.790 VCMOUT (V) 0 VCMOUT (V) DNL (LSB) INTERNAL REFERENCE VOLTAGE vs. TEMPERATURE MAX1438B toc32 1.2530 MAX1438B toc31 0.5 INTERNAL REFERENCE VOLTAGE vs. SUPPLY VOLTAGE MAX1438B toc33 DIFFERENTIAL NONLINEARITY vs. DIGITAL OUTPUT CODE 0.785 0.780 0.6 0.5 0.4 0.3 0.2 0.775 0.1 0 0.770 -40 -15 10 35 TEMPERATURE (NC) 60 85 0 500 1000 1500 2000 ICMOUT(FA) _______________________________________________________________________________________ 9 MAX1438B Typical Operating Characteristics (continued) (VAVDD = 1.8V, VOVDD = 1.8V, VCVDD = 1.8V, VGND = 0V, internal reference, differential input at -0.5dBFS, fIN = 5.3MHz, fCLK = 64MHz (50% duty cycle), DT = 0, CLOAD = 10pF, TA = +25°C, unless otherwise noted.) Octal, 12-Bit, 64Msps, 1.8V ADC with Serial LVDS Outputs MAX1438B Pin Description PIN NAME FUNCTION 1 IN1P Channel 1 Positive Input 2 IN1N Channel 1 Negative Input 3 IN2P Channel 2 Positive Input 4 IN2N Channel 2 Negative Input 5 IN3P Channel 3 Positive Input 6 IN3N Channel 3 Negative Input 7, 8, 10, 11, 25, 26, 27, 60 AVDD Analog Power Input. Connect AVDD to a 1.7V to 1.9V power supply. Bypass AVDD to GND with a 0.1µF capacitor as close as possible to the device. Bypass the AVDD power plane to the GND plane with a bulk capacitor of at least 2.2µF. Connect all AVDD pins to the same potential. 9, 18, 68 GND Ground. Connect all GND pins to the same potential. 12 IN4P Channel 4 Positive Input 13 IN4N Channel 4 Negative Input 14 IN5P Channel 5 Positive Input 15 IN5N Channel 5 Negative Input 16 IN6P Channel 6 Positive Input 17 IN6N Channel 6 Negative Input 19 IN7P Channel 7 Positive Input 20 IN7N Channel 7 Negative Input 21 DT 22 SLVS/LVDS 23 CVDD 24 CLK Double Termination Select. Force DT high to select the internal 100Ω termination between the differential output pairs. Force DT low to select no internal output termination. Differential Output Signal Format Select Input. Force SLVS/LVDS high to select SLVS outputs. Force SLVS/LVDS low to select LVDS outputs. Clock Power Input. Connect CVDD to a 1.7V to 3.5V supply. Bypass CVDD to GND with a 0.1µF capacitor in parallel with a capacitor of at least 2.2µF. Install the bypass capacitors as close as possible to the device. CVDD is used to bias ESD-protection diodes on CLK (see Figure 2). Single-Ended CMOS Clock Input Output Driver Power Input. Connect OVDD to a 1.7V to 1.9V power supply. Bypass OVDD to GND with a 0.1µF capacitor as close as possible to the device. Bypass the OVDD power plane to the GND plane with a bulk capacitor of at least 2.2µF. Connect all OVDD pins to the same potential. 28, 31, 34, 39, 44, 49, 52 OVDD 29 OUT7N Channel 7 Negative LVDS/SLVS Output 30 OUT7P Channel 7 Positive LVDS/SLVS Output 32 OUT6N Channel 6 Negative LVDS/SLVS Output 33 OUT6P Channel 6 Positive LVDS/SLVS Output 35 OUT5N Channel 5 Negative LVDS/SLVS Output 36 OUT5P Channel 5 Positive LVDS/SLVS Output 37 OUT4N Channel 4 Negative LVDS/SLVS Output 38 OUT4P Channel 4 Positive LVDS/SLVS Output 40 FRAMEN Negative Frame-Alignment LVDS/SLVS Output. A rising edge on the differential FRAME output aligns to a valid D0 in the output data stream. 41 FRAMEP Positive Frame-Alignment LVDS/SLVS Output. A rising edge on the differential FRAME output aligns to a valid D0 in the output data stream. 42 CLKOUTN 10 Negative LVDS/SLVS Serial Clock Output ______________________________________________________________________________________ Octal, 12-Bit, 64Msps, 1.8V ADC with Serial LVDS Outputs PIN NAME 43 CLKOUTP FUNCTION 45 OUT3N Channel 3 Negative LVDS/SLVS Output 46 OUT3P Channel 3 Positive LVDS/SLVS Output 47 OUT2N Channel 2 Negative LVDS/SLVS Output 48 OUT2P Channel 2 Positive LVDS/SLVS Output 50 OUT1N Channel 1 Negative LVDS/SLVS Output 51 OUT1P Channel 1 Positive LVDS/SLVS Output 53 OUT0N Channel 0 Negative LVDS/SLVS Output 54 OUT0P Channel 0 Positive LVDS/SLVS Output 55 LVDSTEST LVDS Test Pattern Enable. Force LVDSTEST high to enable the output test pattern, 0000 1011 1101. As with the analog conversion results, the test pattern data are output LSB first. Force LVDSTEST low for normal operation. 56 STBY Standby Input. Force STBY high to put the MAX1438B into standby mode. In standby, the reference circuitry remains active. Force STBY low for normal operation. 57 PLL3 PLL Control Input 3. See Table 1 for details. 58 PLL2 PLL Control Input 2. See Table 1 for details. 59 PLL1 PLL Control Input 1. See Table 1 for details. 61 REFN Negative Reference Bypass Output. Connect a capacitor of at least 1µF (10µF typ) between REFP and REFN, and connect a capacitor of at least 1µF (10µF typ) between REFN and GND. Place the capacitors as close as possible to the device on the same side of the PCB as the MAX1438B. 62 REFP Positive Reference Bypass Output. Connect a capacitor of at least 1µF (10µF typ) between REFP and REFN, and connect a capacitor of at least 1µF (10µF typical) between REFN and GND. Place the capacitors as close as possible to the device on the same side of the PCB as the MAX1438B. 63 REFIO Reference Input/Output. For internal reference operation (REFADJ = GND), the reference output voltage is 1.24V. For external reference operation (REFADJ = AVDD), apply a stable reference voltage at REFIO. Bypass to GND with a capacitor of at least 0.1µF. 64 REFADJ Internal/External Reference Mode Select and Reference Adjust Input. For internal reference, connect REFADJ to GND. For external reference, connect REFADJ to AVDD. For adjusting the reference, see the Full-Scale Range Adjustments Using the Internal Reference section. 65 CMOUT Common-Mode Reference Voltage Output. CMOUT outputs the input common-mode voltage for DC-coupled applications. Bypass CMOUT to GND with a capacitor of at least 0.1µF. Positive LVDS/SLVS Serial-Clock Output 66 IN0P Channel 0 Positive Input 67 IN0N Channel 0 Negative Input — EP Exposed Pad. Internally connected to GND. Connect EP to a large ground plane for maximum thermal performance. Must be connected to GND. ______________________________________________________________________________________ 11 MAX1438B Pin Description (continued) MAX1438B Octal, 12-Bit, 64Msps, 1.8V ADC with Serial LVDS Outputs Functional Diagram REFADJ REFIO REFP REFN STBY REFERENCE SYSTEM POWER CONTROL CMOUT AVDD OVDD DT MAX1438B SLVS/LVDS OUTPUT CONTROL LVDSTEST ICMV* T/H 12-BIT PIPELINE ADC 12:1 SERIALIZER OUT0P 12-BIT PIPELINE ADC 12:1 SERIALIZER OUT1P T/H IN0P IN0N IN1P IN1N OUT0N OUT1N LVDS/SLVS OUTPUT DRIVERS IN7P 12-BIT PIPELINE ADC T/H IN7N OUT7P 12:1 SERIALIZER OUT7N FRAMEP FRAMEN CLK CLOCK CIRCUITRY CVDD CLKOUTP PLL 6x PLL1 PLL2 CLKOUTN PLL3 GND *ICMV = INPUT COMMON-MODE VOLTAGE (INTERNALLY GENERATED). Detailed Description The MAX1438B ADC features fully differential inputs, a pipelined architecture, and digital error correction for high-speed signal conversion. The ADC pipeline architecture moves the samples taken at the inputs through the pipeline stages every half clock cycle. The converted digital results are serialized and sent through the LVDS/SLVS output drivers. The total clock-cycle latency from input to output is 6.5 clock cycles. The MAX1438B offers 8 separate fully differential channels with synchronized inputs and outputs. Global standby minimizes power consumption. 12 Input Circuit Figure 1 displays a simplified diagram of the input T/H circuits. In track mode, switches S1, S2a, S2b, S4a, S4b, S5a, and S5b are closed. The fully differential circuits sample the input signals onto the two capacitors (C2a and C2b) through switches S4a and S4b. S2a and S2b set the common mode for the operational transconductance amplifier (OTA), and open simultaneously with S1, sampling the input waveform. Switches S4a, S4b, S5a, and S5b are then opened before switches S3a and S3b connect capacitors C1a and C1b to the output of the amplifier and switch S4c is closed. The resulting differential voltages are held on capacitors C2a and C2b. The amplifiers charge capacitors C1a and C1b to the same values originally held on C2a and C2b. These values are ______________________________________________________________________________________ Octal, 12-Bit, 64Msps, 1.8V ADC with Serial LVDS Outputs MAX1438B SWITCHES SHOWN IN TRACK MODE INTERNAL COMMON-MODE BIAS* AVDD INTERNALLY GENERATED COMMON-MODE LEVEL* INTERNAL BIAS* S5a S2a MAX1438B C1a S3a S4a C2a IN_P OUT S4c OTA S1 OUT IN_N S4b C2b C1b S3b GND S2b INTERNAL COMMON-MODE BIAS* INTERNAL BIAS* S5b INTERNALLY GENERATED COMMON-MODE LEVEL* *NOT EXTERNALLY ACCESSIBLE. Figure 1. Internal Input Circuit then presented to the first-stage quantizers and isolate the pipelines from the fast-changing inputs. Analog inputs, IN_P to IN_N, are driven differentially. For differential inputs, balance the input impedance of IN_P and IN_N for optimum performance. Reference Configurations (REFIO, REFADJ, REFP, and REFN) The MAX1438B provides an internal 1.24V bandgap reference or can be driven with an external reference voltage. The full-scale analog differential input range is ±FSR. FSR (full-scale range) is given by the following equation: FSR = (0.700 × VREFIO ) 1.24V where VREFIO is the voltage at REFIO, generated internally or externally. For a VREFIO = 1.24V, the full-scale input range is ±700mV (1.4VP-P). Internal Reference Mode Connect REFADJ to GND to use the internal bandgap reference directly. The internal bandgap reference generates VREFIO to be 1.24V with a 120ppm/°C temperature coefficient in internal reference mode. Connect an external ≥ 0.1µF bypass capacitor from REFIO to GND for stability. REFIO sources up to 200µA and sinks up to 200µA for external circuits, and REFIO has a 75mV/mA load regulation. Putting the MAX1438B into standby mode turns off all circuitry except the reference circuit, allowing the converter to power up faster when the ADC exits standby with a high-to-low transitional signal on STBY. The internal circuits of the MAX1438B require 200µs to power up and settle when the converter exits standby mode. To compensate for gain errors or to decrease or increase the ADC’s FSR, add an external resistor between REFADJ and GND or REFADJ and REFIO. This adjusts the internal reference value of the MAX1438B by up to ±5% of its nominal value. See the Full-Scale Range Adjustments Using the Internal Reference section. ______________________________________________________________________________________________________ 13 MAX1438B Octal, 12-Bit, 64Msps, 1.8V ADC with Serial LVDS Outputs Connect ≥ 1µF (10µF typ) capacitors to GND from REFP and REFN and a ≥ 1µF (10µF typ) capacitor between REFP and REFN as close as possible to the device on the same side of the PCB. External Reference Mode The external reference mode allows for more control over the MAX1438B reference voltage and allows multiple converters to use a common reference. Connect REFADJ to AVDD to disable the internal reference. Apply a stable 1.18V to 1.30V source at REFIO. Bypass REFIO to GND with a ≥ 0.1µF capacitor. The REFIO input impedance is > 1MΩ. Table 1. PLL1, PLL2, and PLL3 Configuration Table PLL1 PLL2 PLL3 INPUT CLOCK RANGE (MHz) MIN MAX 0 0 0 45.0 64.0 0 0 1 32.5 45.0 0 1 0 22.5 32.5 0 1 1 16.3 22.5 1 0 0 11.3 16.3 Clock Input (CLK) 1 0 1 8.1 11.3 The MAX1438B accepts a CMOS-compatible clock signal with a wide 20% to 80% input clock duty cycle. Drive CLK with an external single-ended clock signal. Figure 2 shows the simplified clock input diagram. 1 1 0 5.6 8.1 1 1 1 4.0 5.6 Low clock jitter is required for the specified SNR performance of the MAX1438B. Analog input sampling occurs on the rising edge of CLK, requiring this edge to provide the lowest possible jitter. Jitter limits the maximum SNR performance of any ADC according to the following relationship: ⎛ ⎞ 1 SNR = 20 × log ⎜ ⎟ ⎝ 2 × π × fIN × t J ⎠ where fIN represents the analog input frequency and tJ is the total system clock jitter. PLL Inputs (PLL1, PLL2, PLL3) The MAX1438B features a PLL that generates an output clock signal with six times the frequency of the input clock. The output clock signal is used to clock data out of the MAX1438B (see the System Timing Requirements AVDD MAX1438B CVDD CLK GND Figure 2. Clock Input Circuitry 14 DUTY-CYCLE EQUALIZER section). Set the PLL1, PLL2, and PLL3 pins according to the input clock range provided in Table 1. System Timing Requirements Figure 3 shows the relationship between the analog inputs, input clock, frame-alignment output, serial-clock output, and serial-data output. The differential analog input (IN_P and IN_N) is sampled on the rising edge of the CLK signal and the resulting data appears at the digital outputs 6.5 clock cycles later. Figure 4 provides a detailed, two-conversion timing diagram of the relationship between the inputs and the outputs. Clock Output (CLKOUTP, CLKOUTN) The MAX1438B provides a differential clock output that consists of CLKOUTP and CLKOUTN. As shown in Figure 4, the serial output data is clocked out of the MAX1438B on both edges of the clock output. The frequency of the output clock is six times the frequency of CLK. Frame-Alignment Output (FRAMEP, FRAMEN) The MAX1438B provides a differential frame-alignment signal that consists of FRAMEP and FRAMEN. As shown in Figure 4, the rising edge of the frame-alignment signal corresponds to the first bit (D0) of the 12-bit serial data stream. The frequency of the framealignment signal is identical to the frequency of the input clock. Serial Output Data (OUT_P, OUT_N) The MAX1438B provides its conversion results through individual differential outputs consisting of OUT_P and OUT_N. The results are valid 6.5 input clock cycles after the sample is taken. As shown in Figure 3, the output data is clocked out on both edges of the output clock, LSB (D0) first. Figure 5 provides the detailed serial-output timing diagram. ______________________________________________________________________________________ Octal, 12-Bit, 64Msps, 1.8V ADC with Serial LVDS Outputs MAX1438B N+2 N+6 N+3 N (VIN_P VIN_N) N+8 N+5 N+1 N+9 N+7 N+4 tSAMPLE CLK 6.5 CLOCK-CYCLE DATA LATENCY (VFRAMEP VFRAMEN)* (VCLKOUTP VCLKOUTN) (VOUT_P VOUT_N) OUTPUT DATA FOR SAMPLE N-6 OUTPUT DATA FOR SAMPLE N *DUTY CYCLE VARIES DEPENDING ON INPUT CLOCK FREQUENCY. Figure 3. Global Timing Diagram N+2 N (VIN_P - VIN_N) N+1 tSF tSAMPLE CLK (VFRAMEP VFRAMEN)* tCF (VCLKOUTP VCLKOUTN) (VOUT_P VOUT_N) D5N-7 D6N-7 D7N-7 D8N-7 D9N-7 D10N-7 D11N-7 D0N-6 D1N-6 D2N-6 D3N-6 D4N-6 D5N-6 D6N-6 D7N-6 D8N-6 D9N-6 D10N-6 D11N-6 D0N-5 D1N-5 D2N-5 D3N-5 D4N-5 D5N-5 D6N-5 *DUTY CYCLE DEPENDS ON INPUT CLOCK FREQUENCY. Figure 4. Detailed Two-Conversion Timing Diagram tCH tCL (VCLKOUTP VCLKOUTN) (VOUT_P VOUT_N) tOD D0 D1 tOD D2 D3 Figure 5. Serialized-Output Detailed Timing Diagram ______________________________________________________________________________________ 15 Table 2. Output Code Table (VREFIO = 1.24V) TWO’S-COMPLEMENT DIGITAL OUTPUT CODE VIN_P - VIN_N (mV) (VREFIO = 1.24V) BINARY D11 → D0 HEXADECIMAL EQUIVALENT OF D11 → D0 DECIMAL EQUIVALENT OF D11 → D0 0111 1111 1111 0x7FF +2047 +699.66 0111 1111 1110 0x7FE +2046 +699.32 0000 0000 0001 0x001 +1 +0.34 0000 0000 0000 0x000 0 0 1111 1111 1111 0xFFF -1 -0.34 1000 0000 0001 0x801 -2047 -699.66 1000 0000 0000 0x800 -2048 -700.00 1 LSB = 2 x FSR 4096 FSR = 700mV x VREFIO 1.24V FSR TWO'S-COMPLEMENT OUTPUT CODE (LSB) MAX1438B Octal, 12-Bit, 64Msps, 1.8V ADC with Serial LVDS Outputs FSR 0x7FF 0x7FE 0x7FD 0x001 0x000 0xFFF 0x803 0x802 0x801 0x800 -2047 -2045 -1 0 +1 +2045 +2047 DIFFERENTIAL INPUT VOLTAGE (LSB) Figure 6. Two’s-Complement Transfer Function Output Data Transfer Function The MAX1438B output data format is two’s complement. The following equation, Table 2, and Figure 6 define the relationship between the digital output and the analog input: VIN _ P − VIN _ N = FSR × 2 × CODE10 4096 where CODE10 is the decimal equivalent of the digital output code as shown in Table 2. 16 Keep the capacitive load on the MAX1438B digital outputs as low as possible. LVDS and SLVS Selection (SLVS/LVDS) Drive SLVS/LVDS low for LVDS or drive SLVS/LVDS high for SLVS levels at the MAX1438B outputs (OUT_P, OUT_N, CLKOUTP, CLKOUTN, FRAMEP, and FRAMEN). For SLVS levels, enable double-termination by driving DT high. See the Electrical Characteristics table for LVDS and SLVS output voltage levels. ______________________________________________________________________________________ Octal, 12-Bit, 64Msps, 1.8V ADC with Serial LVDS Outputs DT OUT_P/ CLKOUTP/ FRAMEP Common-Mode Output (CMOUT) CMOUT provides a common-mode reference for DCcoupled analog inputs. If the input is DC-coupled, match the output common-mode voltage of the circuit driving the MAX1438B to the output voltage at VCMOUT to within ±50mV. It is recommended that the output common-mode voltage of the driving circuit be derived from CMOUT. Standby Mode The MAX1438B offers a standby mode to efficiently use power by transitioning to a low-power state when conversions are not required. STBY controls the standby mode of all channels and the internal reference circuitry. The reference does not power down in standby mode. Drive STBY high to enable standby. In standby mode, the output impedance of all of the LVDS/SLVS outputs is approximately 342Ω, if DT is low. The output impedance of the differential LVDS/SLVS outputs is 100Ω when DT is high. See the Electrical Characteristics table for typical supply currents during standby. The following list shows the state of the analog inputs and digital outputs in standby mode: • IN_P, IN_N analog inputs are disconnected from the internal input amplifier. • Reference circuit remains active. • OUT_P, OUT_N, CLKOUTP, CLKOUTN, FRAMEP, and FRAMEN have approximately 342Ω between the output pairs when DT is low. When DT is high, the differential output pairs have 100Ω between each pair. When operating in internal reference mode, the MAX1438B requires 200µs to power up and settle when Z0 = 50Ω 100Ω Double Termination (DT) The MAX1438B offers an optional, internal 100Ω termination between the differential output pairs (OUT_P and OUT_N, CLKOUTP and CLKOUTN, FRAMEP and FRAMEN). In addition to the termination at the end of the line, a second termination directly at the outputs helps eliminate unwanted reflections down the line. This feature is useful in applications where trace lengths are long (> 5in) or with mismatched impedance. Drive DT high to select double-termination, or drive DT low to disconnect the internal termination resistor (single-termination). Selecting double-termination increases the OVDD supply current (see Figure 7). MAX1438B LVDS Test Pattern (LVDSTEST) Drive LVDSTEST high to enable the output test pattern on all LVDS or SLVS output channels. The output test pattern is 0000 1011 1101. Drive LVDSTEST low for normal operation (test pattern disabled). MAX1438B 100Ω OUT_N/ CLKOUTN/ FRAMEN Z0 = 50Ω SWITCHES ARE CLOSED WHEN DT IS HIGH. SWITCHES ARE OPEN WHEN DT IS LOW. Figure 7. Double Termination the converter exits standby mode. To exit standby mode, STBY, the applied control signal must transition from high to low. When using an external reference, the wakeup time is dependent on the external reference drivers. Applications Information Full-Scale Range Adjustments Using the Internal Reference The MAX1438B supports a full-scale adjustment range of 10% (±5%). To decrease the full-scale range, add a 25kΩ to 250kΩ external resistor or potentiometer (RADJ) between REFADJ and GND. To increase the full-scale range, add a 25kΩ to 250kΩ resistor between REFADJ and REFIO. Figure 8 shows the two possible configurations. The following equations provide the relationship between RADJ and the change in the analog full-scale range: ⎛ 1.25kΩ ⎞ FSR = 0.7V ⎜ 1 + RADJ ⎟⎠ ⎝ for RADJ connected between REFADJ and REFIO, and: ⎛ 1.25kΩ ⎞ FSR = 0.7V ⎜ 1 − RADJ ⎟⎠ ⎝ for RADJ connected between REFADJ and GND. ______________________________________________________________________________________________________ 17 MAX1438B Octal, 12-Bit, 64Msps, 1.8V ADC with Serial LVDS Outputs 10Ω ADC FULL-SCALE = REFT - REFB REFT 0.1µF G REFB REFERENCESCALING AMPLIFIER 6 39pF T1 N.C. 2 5 MAX1438B 0.1µF REFERENCE BUFFER REFIO 3 4 MINICIRCUITS ADT1-1WT 0.1µF 10Ω IN_N 1V REFADJ 25kΩ TO 250kΩ CONTROL LINE TO DISABLE REFERENCE BUFFER MAX1438B AVCC 39pF Figure 9. Transformer-Coupled Input Drive 25kΩ TO 250kΩ AVCC/2 Figure 8. Circuit Suggestions to Adjust the ADC’s Full-Scale Range Using Transformer Coupling An RF transformer (Figure 9) provides an excellent solution to convert a single-ended input source signal to a fully differential signal. The MAX1438B input common-mode voltage is internally biased to 0.76V (typ) with f CLK = 64MHz. Although a 1:1 transformer is shown, a step-up transformer can be selected to reduce the drive requirements. A reduced signal swing from the input driver, such as an op amp, can also improve the overall distortion. Grounding, Bypassing, and Board Layout The MAX1438B requires high-speed board layout design techniques. Refer to the MAX1438B EV kit data sheet for a board layout reference. Locate all bypass capacitors as close as possible to the device, preferably on the same side as the ADC, using surface-mount devices for minimum inductance. Bypass AVDD to GND with a 0.1µF ceramic capacitor in parallel with a 0.1µF ceramic capacitor. Bypass OVDD to GND with a 0.1µF ceramic capacitor in parallel with a ≥ 2.2µF ceramic capacitor. Bypass CVDD to GND with a 0.1µF ceramic capacitor in parallel with a ≥ 2.2µF ceramic capacitor. Multilayer boards with ample ground and power planes produce the highest level of signal integrity. Connect 18 IN_P 1 VIN the MAX1438B ground pins and the exposed backside pad to the same ground plane. The MAX1438B relies on the exposed-backside-pad connection for a lowinductance ground connection. Isolate the ground plane from any noisy digital system ground planes. Route high-speed digital signal traces away from the sensitive analog traces. Keep all signal lines short and free of 90° turns. Ensure that the differential analog input network layout is symmetric and that all parasitics are balanced equally. Refer to the MAX1438B EV kit data sheet for an example of symmetric input layout. Parameter Definitions Integral Nonlinearity (INL) INL is the deviation of the values on an actual transfer function from a straight line. For the MAX1438B, this straight line is between the end points of the transfer function, once offset and gain errors have been nullified. INL deviations are measured at every step and the worst-case deviation is reported in the Electrical Characteristics table. Differential Nonlinearity (DNL) DNL is the difference between an actual step width and the ideal value of 1 LSB. A DNL error specification of less than 1 LSB guarantees no missing codes and a monotonic transfer function. For the MAX1438B, DNL deviations are measured at every step and the worstcase deviation is reported in the Electrical Characteristics table. ______________________________________________________________________________________ Octal, 12-Bit, 64Msps, 1.8V ADC with Serial LVDS Outputs MAX1438B Offset Error Offset error is a figure of merit that indicates how well the actual transfer function matches the ideal transfer function at a single point. For the MAX1438B, the ideal midscale digital output transition occurs when there is -1/2 LSBs across the analog inputs (Figure 6). Bipolar offset error is the amount of deviation between the measured midscale transition point and the ideal midscale transition point. CLK tAD ANALOG INPUT tAJ SAMPLED DATA Gain Error Gain error is a figure of merit that indicates how well the slope of the actual transfer function matches the slope of the ideal transfer function. For the MAX1438B, the gain error is the difference of the measured full-scale and zero-scale transition points minus the difference of the ideal full-scale and zero-scale transition points. For the bipolar device (MAX1438B), the full-scale transition point is from 0x7FE to 0x7FF and the zero-scale transition point is from 0x800 to 0x801. Crosstalk Crosstalk indicates how well each analog input is isolated from the others. For the MAX1438B, a 5.3MHz, -0.5dBFS analog signal is applied to 1 channel while a 30.3MHz, -0.5dBFS analog signal is applied to another channel. An FFT is taken on the channel with the 5.3MHz analog signal. From this FFT, the crosstalk is measured as the difference in the 5.3MHz and 30.3MHz amplitudes. Aperture Delay Aperture delay (tAD) is the time defined between the rising edge of the sampling clock and the instant when an actual sample is taken. See Figure 10. T/H HOLD TRACK HOLD Figure 10. Aperture Jitter/Delay Specifications includes all spectral components to the Nyquist frequency excluding the fundamental, the first six harmonics (HD2–HD7), and the DC offset. Signal-to-Noise Plus Distortion (SINAD) SINAD is computed by taking the ratio of the RMS signal to the RMS noise plus distortion. RMS noise plus distortion includes all spectral components to the Nyquist frequency, excluding the fundamental and the DC offset. Effective Number of Bits (ENOB) ENOB specifies the dynamic performance of an ADC at a specific input frequency and sampling rate. An ideal ADC’s error consists of quantization noise only. ENOB for a full-scale sinusoidal input waveform is computed from: ⎛ SINAD − 1.76 ⎞ ENOB = ⎜ ⎟⎠ ⎝ 6.02 Aperture Jitter Aperture jitter (tAJ) is the sample-to-sample variation in the aperture delay. See Figure 10. Signal-to-Noise Ratio (SNR) For a waveform perfectly reconstructed from digital samples, the theoretical maximum SNR is the ratio of the full-scale analog input (RMS value) to the RMS quantization error (residual error). The ideal, theoretical minimum analog-to-digital noise is caused by quantization error only and results directly from the ADC’s resolution (N bits): SNRdB[max] = 6.02dB x N + 1.76dB In reality, there are other noise sources besides quantization noise: thermal noise, reference noise, clock jitter, etc. For the MAX1438B, SNR is computed by taking the ratio of the RMS signal to the RMS noise. RMS noise Total Harmonic Distortion (THD) THD is the ratio of the RMS sum of the first six harmonics of the input signal to the fundamental itself. This is expressed as: ⎛ V 2+V 2+V 2+V 2+V 2+V 2⎞ 3 4 5 6 7 ⎟ THD = 20 × log ⎜ 2 ⎜ ⎟ V1 ⎝ ⎠ Spurious-Free Dynamic Range (SFDR) SFDR is the ratio expressed in decibels of the RMS amplitude of the fundamental (maximum signal component) to the RMS value of the next-largest spurious component, excluding DC offset. SFDR is specified in decibels relative to the carrier (dBc). ______________________________________________________________________________________ 19 MAX1438B Octal, 12-Bit, 64Msps, 1.8V ADC with Serial LVDS Outputs Intermodulation Distortion (IMD) Full-Power Bandwidth IMD is the total power of the IM2 to IM5 intermodulation products to the Nyquist frequency relative to the total input power of the two input tones, f1 and f2. The individual input tone levels are at -6.5dBFS. The intermodulation products are as follows: • 2nd-order intermodulation products (IM2): f1 + f2, f2 - f1 A large -0.5dBFS analog input signal is applied to an ADC, and the input frequency is swept up to the point where the amplitude of the digitized conversion result has decreased by -3dB. This point is defined as fullpower input bandwidth frequency. • 3rd-order intermodulation products (IM3): 2 x f1 - f2, 2 x f2 - f1, 2 x f1 + f2, 2 x f2 + f1 • 4th-order intermodulation products (IM4): 3 x f1 - f2, 3 x f2 - f1, 3 x f1 + f2, 3 x f2 + f1 • 5th-order intermodulation products (IM5): 3 x f1 - 2 x f2, 3 x f2 - 2 x f1, 3 x f1 + 2 x f2, 3 x f2 + 2 x f1 Third-Order Intermodulation (IM3) IM3 is the total power of the 3rd-order intermodulation product to the Nyquist frequency relative to the total input power of the two input tones, f1 and f2. The individual input tone levels are at -6.5dBFS. The 3rd-order intermodulation products are 2 x f1 - f2, 2 x f2 - f1, 2 x f1 + f2, 2 x f2 + f1. Small-Signal Bandwidth A small -20.5dBFS analog input signal is applied to an ADC so that the signal’s slew rate does not limit the ADC’s performance. The input frequency is then swept up to the point where the amplitude of the digitized conversion result has decreased by -3dB. 20 Gain Matching Gain matching is a figure of merit that indicates how well the gain of all 8 ADC channels is matched to each other. For the MAX1438B, gain matching is measured by applying the same 5.3MHz, -0.5dBFS analog signal to all analog input channels. These analog inputs are sampled at 64Msps and the maximum deviation in amplitude is reported in dB as gain matching in the Electrical Characteristics table. Phase Matching Phase matching is a figure of merit that indicates how well the phases of all 8 ADC channels are matched to each other. For the MAX1438B, phase matching is measured by applying the same 5.3MHz, -0.5dBFS analog signal to all analog input channels. These analog inputs are sampled at 64Msps and the maximum deviation in phase is reported in degrees as phase matching in the Electrical Characteristics table. ______________________________________________________________________________________ Octal, 12-Bit, 64Msps, 1.8V ADC with Serial LVDS Outputs OUT0P OUT0N OVDD PLL2 PLL3 STBY LVDSTEST CMOUT REFADJ REFIO REFP REFN AVDD PLL1 IN0N IN0P GND TOP VIEW 68 67 66 65 64 63 62 61 60 59 58 57 56 55 54 53 52 IN1P 1 IN1N IN2P 2 3 49 IN2N IN3P IN3N 4 48 5 47 6 46 AVDD AVDD GND 7 45 9 43 AVDD 10 42 AVDD 11 IN4P 12 IN4N 13 41 51 50 + MAX1438B 8 IN5P IN5N 14 IN6P IN6N 16 44 40 39 38 EXPOSED PAD. CONNECTED TO GND. 15 37 17 OUT1P OUT1N OVDD OUT2P OUT2N OUT3P OUT3N OVDD CLKOUTP CLKOUTN FRAMEP FRAMEN OVDD OUT4P 36 OUT4N OUT5P 35 OUT5N OVDD OUT6P AVDD AVDD OVDD OUT7N OUT7P OVDD OUT6N AVDD GND IN7P IN7N DT SLVS/LVDS CVDD CLK 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 TQFN (10mm x 10mm x 0.8mm) Package Information For the latest package outline information and land patterns, go to www.maxim-ic.com/packages. PACKAGE TYPE PACKAGE CODE DOCUMENT NO. 68 TQFN-EP T6800-4 21-0142 Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are implied. Maxim reserves the right to change the circuitry and specifications without notice at any time. Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 ____________________ 21 © 2009 Maxim Integrated Products Maxim is a registered trademark of Maxim Integrated Products, Inc. MAX1438B Pin Configuration