19-3643; Rev 0; 4/05 KIT ATION EVALU E L B AVAILA Dual, 80Msps, 12-Bit, IF/Baseband ADC The MAX12528 is a dual 80Msps, 12-bit analog-to-digital converter (ADC) featuring fully differential wideband track-and-hold (T/H) inputs, driving internal quantizers. The MAX12528 is optimized for low power, small size, and high dynamic performance in intermediate frequency (IF) and baseband sampling applications. This dual ADC operates from a single 3.3V supply, consuming only 726mW while delivering a typical 69.8dB signal-tonoise ratio (SNR) performance at a 175MHz input frequency. The T/H input stages accept single-ended or differential inputs up to 400MHz. In addition to low operating power, the MAX12528 features a 330W powerdown mode to conserve power during idle periods. A flexible reference structure allows the MAX12528 to use the internal 2.048V bandgap reference or accept an externally applied reference and allows the reference to be shared between the two ADCs. The reference structure allows the full-scale analog input range to be adjusted from 0.35V to 1.15V. The MAX12528 provides a common-mode reference to simplify design and reduce external component count in differential analog input circuits. The MAX12528 supports either a single-ended or differential input clock. User-selectable divide-by-two (DIV2) and divide-by-four (DIV4) modes allow for design flexibility and help eliminate the negative effects of clock jitter. Wide variations in the clock duty cycle are compensated with the ADC's internal duty-cycle equalizer (DCE). The MAX12528 features two parallel, 12-bit-wide, CMOS-compatible outputs. The digital output format is pin-selectable to be either two's complement or Gray code. A separate power-supply input for the digital outputs accepts a 1.7V to 3.6V voltage for flexible interfacing with various logic levels. The MAX12528 is available in a 10mm x 10mm x 0.8mm, 68-pin thin QFN package with exposed paddle (EP), and is specified for the extended (-40C to +85C) temperature range. Features Direct IF Sampling Up to 400MHz Excellent Dynamic Performance 70.7dB/69.8dB SNR at fIN = 70MHz/175MHz 78.2dBc/72.9dBc SFDR at fIN = 70MHz/175MHz 3.3V Low-Power Operation 760mW (Differential Clock Mode) 726mW (Single-Ended Clock Mode) Fully Differential or Single-Ended Analog Input Adjustable Differential Analog Input Voltage 750MHz Input Bandwidth Internal, External, or Shared Reference Differential or Single-Ended Clock Accepts 25% to 75% Clock Duty Cycle User-Selectable DIV2 and DIV4 Clock Modes Power-Down Mode CMOS Outputs in Two's Complement or Gray Code Out-of-Range and Data-Valid Indicators Compact, 68-Pin Thin QFN Package (10mm x 10mm x 0.8mm) Evaluation Kit Available (Order MAX12528EVKIT) Ordering Information PART MAX12528ETK -40C to +85C 68 Thin QFN-EP* Medical Imaging Portable Instrumentation Digital Set-Top Boxes Low-Power Data Acquisition T6800-2 *EP = Exposed paddle. Selector Guide Applications IF and Baseband Communication Receivers Cellular, LMDS, Point-to-Point Microwave, MMDS, HFC, WLAN I/Q Receivers PKG CODE TEMP RANGE PIN-PACKAGE SAMPLING RATE (Msps) RESOLUTION (Bits) MAX12528 80 12 MAX12557 65 14 MAX12527 65 12 PART Pin Configuration appears at end of data sheet. ________________________________________________________________ Maxim Integrated Products For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at 1-888-629-4642, or visit Maxim's website at www.maxim-ic.com. 1 MAX12528 General Description MAX12528 Dual, 80Msps, 12-Bit, IF/Baseband ADC ABSOLUTE MAXIMUM RATINGS VDD to GND ................................................................-0.3V to +3.6V OVDD to GND............-0.3V to the lower of (VDD + 0.3V) and +3.6V INAP, INAN to GND ...-0.3V to the lower of (VDD + 0.3V) and +3.6V INBP, INBN to GND ...-0.3V to the lower of (VDD + 0.3V) and +3.6V CLKP, CLKN to GND ........................-0.3V to the lower of (VDD + 0.3V) and +3.6V REFIN, REFOUT to GND ..................-0.3V to the lower of (VDD + 0.3V) and +3.6V REFAP, REFAN, COMA to GND ......-0.3V to the lower of (VDD + 0.3V) and +3.6V REFBP, REFBN, COMB to GND ......-0.3V to the lower of (VDD + 0.3V) and +3.6V DIFFCLK/SECLK, G/T, PD, SHREF, DIV2, DIV4 to GND .........-0.3V to the lower of (VDD + 0.3V) and +3.6V D0A-D11A, D0B-D11B, DAV, DORA, DORB to GND..............................-0.3V to (OVDD + 0.3V) Continuous Power Dissipation (TA = +70C) 68-Pin Thin QFN 10mm x 10mm x 0.8mm (derate 70mW/C above +70C) ....................................4000mW Thermal Resistance jc........................................................0.4C/W Operating Temperature Range................................-40C to +85C Junction Temperature ...........................................................+150C Storage Temperature Range .................................-65C to +150C Lead Temperature (soldering, 10s)......................................+300C 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 (VDD = 3.3V, OVDD = 2.0V, GND = 0, REFIN = REFOUT (internal reference), CL 10pF at digital outputs, AIN = -0.5dBFS (differential), DIFFCLK/SECLK = OVDD, PD = GND, SHREF = GND, DIV2 = GND, DIV4 = GND, G/T = GND, fCLK = 80MHz, TA = -40C to +85C, unless otherwise noted. Typical values are at TA = +25C.) (Note 1) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS DC ACCURACY Resolution 12 Bits Integral Nonlinearity INL fIN = 3MHz 0.6 1.6 LSB Differential Nonlinearity DNL fIN = 3MHz, no missing codes 0.3 0.85 LSB Offset Error 0.1 0.7 %FSR Gain Error 0.5 4.3 %FSR ANALOG INPUT (INAP, INAN, INBP, INBN) Differential Input Voltage Range VDIFF Differential or single-ended inputs 1.024 Common-Mode Input Voltage Analog Input Resistance RIN CPAR V VDD / 2 V Each input (Figure 3) 2 k Fixed capacitance to ground, each input (Figure 3) 2 Analog Input Capacitance pF CSAMPLE Switched capacitance, each input (Figure 3) 4.5 CONVERSION RATE Maximum Clock Frequency fCLK 80 MHz Minimum Clock Frequency 5 Data Latency Figure 5 MHz 8 Clock Cycles dBFS DYNAMIC CHARACTERISTICS Small-Signal Noise Floor Signal-to-Noise Ratio SSNF SNR Input at -35dBFS 71.0 72.1 fIN = 3MHz at -0.5dBFS 69.3 71.2 fIN = 40MHz at -0.5dBFS 70.7 fIN = 70MHz at -0.5dBFS 70.7 fIN = 175MHz at -0.5dBFS 2 67.1 69.8 _______________________________________________________________________________________ dB Dual, 80Msps, 12-Bit, IF/Baseband ADC (VDD = 3.3V, OVDD = 2.0V, GND = 0, REFIN = REFOUT (internal reference), CL 10pF at digital outputs, AIN = -0.5dBFS (differential), DIFFCLK/SECLK = OVDD, PD = GND, SHREF = GND, DIV2 = GND, DIV4 = GND, G/T = GND, fCLK = 80MHz, TA = -40C to +85C, unless otherwise noted. Typical values are at TA = +25C.) (Note 1) PARAMETER SYMBOL CONDITIONS fIN = 3MHz at -0.5dBFS Signal-to-Noise Plus Distortion Spurious-Free Dynamic Range SINAD SFDR Second Harmonic THD HD2 Third Harmonic HD3 Two-Tone Intermodulation Distortion (Note 2) 3rd-Order Intermodulation Distortion Two-Tone Spurious-Free Dynamic Range Full-Power Bandwidth TTIMD IM3 SFDRTT FPBW Aperture Delay tAD Aperture Jitter tAJ Output Noise nOUT TYP 70.8 fIN = 40MHz at -0.5dBFS 70.2 fIN = 70MHz at -0.5dBFS 69.6 fIN = 175MHz at -0.5dBFS 64.6 fIN = 3MHz at -0.5dBFS 74.7 fIN = 70MHz at -0.5dBFS 78.2 -84.2 fIN = 40MHz at -0.5dBFS -79.3 fIN = 70MHz at -0.5dBFS -75.8 fIN = 175MHz at -0.5dBFS -71.9 fIN = 3MHz at -0.5dBFS -87.2 fIN = 40MHz at -0.5dBFS -85.2 fIN = 70MHz at -0.5dBFS -85 fIN = 175MHz at -0.5dBFS -81.5 fIN = 3MHz at -0.5dBFS -92.1 fIN = 40MHz at -0.5dBFS -85.5 fIN = 70MHz at -0.5dBFS -78.2 fIN = 175MHz at -0.5dBFS -72.9 fIN1 = 68.5MHz at -7dBFS fIN2 = 71.5MHz at -7dBFS -77.5 fIN1 = 172.5MHz at -7dBFS fIN2 = 177.5MHz at -7dBFS -72.8 fIN1 = 68.5MHz at -7dBFS fIN2 = 71.5MHz at -7dBFS -78.6 fIN1 = 172.5MHz at -7dBFS fIN2 = 177.5MHz at -7dBFS -74.3 fIN1 = 68.5MHz at -7dBFS fIN2 = 71.5MHz at -7dBFS 78.6 fIN1 = 172.5MHz at -7dBFS fIN2 = 177.5MHz at -7dBFS 74.3 Input at -0.2dBFS, -3dB rolloff 750 INAP = INAN = COMA INBP = INBN = COMB dB dBc 72.9 fIN = 3MHz at -0.5dBFS Figure 5 UNITS 85.6 81.8 67.2 MAX 67.7 fIN = 40MHz at -0.5dBFS fIN = 175MHz at -0.5dBFS Total Harmonic Distortion MIN 68.9 -73.3 dBc -66.4 dBc dBc dBc dBc dBc MHz 1.2 ns <0.15 psRMS 0.3 LSBRMS _______________________________________________________________________________________ 3 MAX12528 ELECTRICAL CHARACTERISTICS (continued) MAX12528 Dual, 80Msps, 12-Bit, IF/Baseband ADC ELECTRICAL CHARACTERISTICS (continued) (VDD = 3.3V, OVDD = 2.0V, GND = 0, REFIN = REFOUT (internal reference), CL 10pF at digital outputs, AIN = -0.5dBFS (differential), DIFFCLK/SECLK = OVDD, PD = GND, SHREF = GND, DIV2 = GND, DIV4 = GND, G/T = GND, fCLK = 80MHz, TA = -40C to +85C, unless otherwise noted. Typical values are at TA = +25C.) (Note 1) PARAMETER SYMBOL Overdrive Recovery Time CONDITIONS MIN TYP 10% beyond full scale 1 fINA or fINB = 70MHz at -0.5dBFS 90 fINA or fINB = 175MHz at -0.5dBFS 85 MAX UNITS Clock cycle INTERCHANNEL CHARACTERISTICS Crosstalk Rejection Gain Matching 0.01 Offset Matching 0.01 dB 0.1 dB %FSR INTERNAL REFERENCE (REFOUT) REFOUT Output Voltage VREFOUT REFOUT Load Regulation REFOUT Temperature Coefficient 1.995 -1mA < IREFOUT < +1mA TCREF REFOUT Short-Circuit Current 2.048 2.075 V 35 mV/mA 65 ppm/C Short to VDD--sinking 0.24 Short to GND--sourcing 2.1 mA BUFFERED REFERENCE MODE (REFIN is driven by REFOUT or an external 2.048V single-ended reference source; VREFAP/VREFAN/VCOMA and VREFBP/VREFBN/VCOMB are generated internally) REFIN Input Voltage VREFIN 2.048 V REFIN Input Resistance RREFIN >50 M COM_ Output Voltage VCOMA VCOMB VDD / 2 REF_P Output Voltage VREFAP VREFBP VDD / 2 + (VREFIN x 3/8) 2.418 V REF_N Output Voltage VREFAN VREFBN VDD / 2 - (VREFIN x 3/8) 0.882 V Differential Reference Voltage VREFA VREFB Differential Reference Temperature Coefficient TCREF VREFA = VREFAP - VREFAN VREFB = VREFBP - VREFBN 1.60 1.440 1.65 1.536 30 1.70 V 1.590 V ppm/C UNBUFFERED EXTERNAL REFERENCE (REFIN = GND, VREFAP/VREFAN/VCOMA and VREFBP/VREFBN/VCOMB are applied externally, VCOMA = VCOMB = VDD / 2) REF_P Input Voltage VREFAP VREFBP VREF_P - VCOM +0.768 V REF_N Input Voltage VREFAN VREFBN VREF_N - VCOM -0.768 V COM_ Input Voltage VCOM VDD / 2 1.65 V Differential Reference Voltage VREFA VREFB VREF_ = VREF_P - VREF_N = VREFIN x 3/4 1.536 V 4 _______________________________________________________________________________________ Dual, 80Msps, 12-Bit, IF/Baseband ADC (VDD = 3.3V, OVDD = 2.0V, GND = 0, REFIN = REFOUT (internal reference), CL 10pF at digital outputs, AIN = -0.5dBFS (differential), DIFFCLK/SECLK = OVDD, PD = GND, SHREF = GND, DIV2 = GND, DIV4 = GND, G/T = GND, fCLK = 80MHz, TA = -40C to +85C, unless otherwise noted. Typical values are at TA = +25C.) (Note 1) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS REF_P Sink Current IREFAP IREFBP VREF_P = 2.418V 1.2 mA REF_N Source Current IREFAN IREFBN VREF_N = 0.882V 0.85 mA COM_ Sink Current ICOMA ICOMB VCOM_ = 1.65V 0.85 mA REF_P, REF_N Capacitance CREF_P, CREF_N 13 pF COM_ Capacitance CCOM_ 6 pF CLOCK INPUTS (CLKP, CLKN) Single-Ended Input High Threshold Single-Ended Input Low Threshold VIH DIFFCLK/SECLK = GND, CLKN = GND VIL DIFFCLK/SECLK = GND, CLKN = GND 0.8 x VDD V 0.2 x VDD V Minimum Differential Clock Input Voltage Swing DIFFCLK/SECLK = OVDD 0.2 VP-P Differential Input Common-Mode Voltage DIFFCLK/SECLK = OVDD VDD / 2 V CLK_ Input Resistance RCLK Each input (Figure 4) 5 k CLK_ Input Capacitance CCLK Each input 2 pF DIGITAL INPUTS (DIFFCLK/SECLK, G/T, PD, DIV2, DIV4) Input High Threshold VIH Input Low Threshold VIL V 0.2 x OVDD 5 OVDD applied to input Input Leakage Current Digital Input Capacitance 0.8 x OVDD Input connected to ground 5 CDIN 5 V A pF DIGITAL OUTPUTS (D0A-D11A, D0B-D11B, DORA, DORB, DAV) Output-Voltage Low VOL D0A-D11A, D0B-D11B, DORA, DORB: ISINK = 200A 0.2 DAV: ISINK = 600A Output-Voltage High Three-State Leakage Current (Note 3) VOH ILEAK V 0.2 D0A-D11A, D0B-D11B, DORA, DORB: ISOURCE = 200A OVDD 0.2 DAV: ISOURCE = 600A OVDD 0.2 V OVDD applied to input 5 Input connected to ground 5 A _______________________________________________________________________________________ 5 MAX12528 ELECTRICAL CHARACTERISTICS (continued) MAX12528 Dual, 80Msps, 12-Bit, IF/Baseband ADC ELECTRICAL CHARACTERISTICS (continued) (VDD = 3.3V, OVDD = 2.0V, GND = 0, REFIN = REFOUT (internal reference), CL 10pF at digital outputs, AIN = -0.5dBFS (differential), DIFFCLK/SECLK = OVDD, PD = GND, SHREF = GND, DIV2 = GND, DIV4 = GND, G/T = GND, fCLK = 80MHz, TA = -40C to +85C, unless otherwise noted. Typical values are at TA = +25C.) (Note 1) PARAMETER SYMBOL D0A-D11A, DORA, D0B-D11B and DORB Three-State Output Capacitance CONDITIONS MIN TYP MAX UNITS COUT (Note 3) 3 pF DAV Three-State Output Capacitance CDAV (Note 3) 6 pF POWER REQUIREMENTS Analog Supply Voltage Digital Output Supply Voltage Analog Supply Current Analog Power Dissipation Digital Output Supply Current 6 VDD OVDD IVDD PVDD IOVDD 3.15 3.30 3.60 V 1.70 2.0 VDD V Normal operating mode fIN = 175MHz at -0.5dBFS, single-ended clock (DIFFCLK/SECLK = GND) 220 Normal operating mode fIN = 175MHz at -0.5dBFS, differential clock (DIFFCLK/SECLK = OVDD) 230 Power-down mode (PD = OVDD) clock idle 0.1 Normal operating mode fIN = 175MHz at -0.5dBFS, single-ended clock (DIFFCLK/SECLK = GND) 726 Normal operating mode fIN = 175MHz at -0.5dBFS, differential clock (DIFFCLK/SECLK = OVDD) 760 mA 250 mW Power-down mode (PD = OVDD) clock idle 0.330 Normal operating mode fIN = 175MHz at -0.5dBFS 20.7 Power-down mode (PD = OVDD) clock idle 0.004 825 mA _______________________________________________________________________________________ Dual, 80Msps, 12-Bit, IF/Baseband ADC (VDD = 3.3V, OVDD = 2.0V, GND = 0, REFIN = REFOUT (internal reference), CL 10pF at digital outputs, AIN = -0.5dBFS (differential), DIFFCLK/SECLK = OVDD, PD = GND, SHREF = GND, DIV2 = GND, DIV4 = GND, G/T = GND, fCLK = 80MHz, TA = -40C to +85C, unless otherwise noted. Typical values are at TA = +25C.) (Note 1) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS TIMING CHARACTERISTICS (Figure 5) Clock Pulse-Width High tCH 6.2 ns tCL 6.2 ns tDAV 5.3 ns Clock Pulse-Width Low Data-Valid Delay Data Setup Time Before Rising Edge of DAV tSETUP (Note 4) 5.0 ns Data Hold Time After Rising Edge of DAV tHOLD (Note 4) 5.5 ns Wake-Up Time from Power-Down tWAKE VREFIN = 2.048V 10 ms Note 1: Specifications +25C guaranteed by production test, <+25C guaranteed by design and characterization. Note 2: Two-tone intermodulation distortion measured with respect to a single-carrier amplitude, and not the peak-to-average input power of both input tones. Note 3: During power-down, D0A-D11A, D0B-D11B, DORA, DORB, and DAV are high impedance. Note 4: Guaranteed by design and characterization. Typical Operating Characteristics (VDD = 3.3V, OVDD = 2.0V, GND = 0, REFIN = REFOUT (internal reference mode), CL 5pF at digital outputs, AIN = -0.5dBFS, DIFFCLK/SECLK = OVDD, PD = GND, G/T = GND, fCLK = 80MHz (50% duty cycle), TA = +25C, unless otherwise noted.) AMPLITUDE (dBFS) -40 -50 -60 -70 HD2 HD3 -80 -90 -100 -110 -120 -30 -40 -50 -60 -70 -80 -90 5 10 15 20 25 30 35 ANALOG INPUT FREQUENCY (MHz) 40 fCLK = 80MHz fIN = 69.8999023MHz AIN = -0.437dBFS fIN SNR = 71dB SINAD = 69.2dB THD = -73.9dBc SFDR = 74.6dBc HD2 = -94.6dBc HD3 = -74.6dBc HD3 HD2 -10 -20 -30 HD3 HD2 -40 -50 -60 -70 -80 -90 MAX12528 toc03 fIN -100 -110 -120 0 FFT PLOT (32,768-POINT DATA RECORD) 0 AMPLITUDE (dBFS) fIN -30 fCLK = 80MHz fIN = 39.5092773MHz AIN = -0.482dBFS SNR = 71.1dB SINAD = 70.5dB THD = -79.1dBc SFDR = 82.7dBc HD2 = -87.6dBc HD3 = -82.7dBc -10 -20 AMPLITUDE (dBFS) fCLK = 80MHz fIN = 2.99926758MHz AIN = -0.46dBFS SNR = 70.9dB SINAD = 70.7dB THD = -84dBc SFDR = 85.5dBc HD2 = -86dBc HD3 = -101dBc MAX12528 toc01 -10 -20 FFT PLOT (32,768-POINT DATA RECORD) 0 MAX12528 toc02 FFT PLOT (16,384-POINT DATA RECORD) 0 -100 -110 -120 0 5 10 15 20 25 30 35 ANALOG INPUT FREQUENCY (MHz) 40 0 5 10 15 20 25 30 35 40 ANALOG INPUT FREQUENCY (MHz) _______________________________________________________________________________________ 7 MAX12528 ELECTRICAL CHARACTERISTICS (continued) Typical Operating Characteristics (continued) (VDD = 3.3V, OVDD = 2.0V, GND = 0, REFIN = REFOUT (internal reference mode), CL 5pF at digital outputs, AIN = -0.5dBFS, DIFFCLK/SECLK = OVDD, PD = GND, G/T = GND, fCLK = 80MHz (50% duty cycle), TA = +25C, unless otherwise noted.) TWO-TONE IMD PLOT (16,384-POINT DATA RECORD) -40 -50 -60 -70 -80 -90 HD2 -60 2fIN2 + fIN1 -80 10 15 20 25 35 fIN1 + fIN2 -80 5 10 15 20 25 30 0 5 10 15 20 25 30 INTEGRAL NONLINEARITY vs. DIGITAL OUTPUT CODE DIFFERENTIAL NONLINEARITY vs. DIGITAL OUTPUT CODE SNR, SINAD vs. ANALOG INPUT FREQUENCY (fCLK = 80MHz, AIN = -0.5dBFS) 0.6 0.2 -0.2 SNR 70 68 66 SNR, SINAD (dB) 0.2 DNL (LSB) 0.4 0 fCLK = 80MHz fIN = 2.1655273MHz 0.8 72 MAX12528 toc08 1.0 MAX12528 toc09 ANALOG INPUT FREQUENCY (MHz) 0.4 0 -0.2 64 62 60 SINAD 58 -0.4 -0.4 56 -0.6 -0.6 54 -0.8 -0.8 52 -1.0 -1.0 0 fIN2 fIN2 - fIN1 ANALOG INPUT FREQUENCY (MHz) 0.6 50 512 1024 1536 2048 2560 3072 3584 4096 0 512 1024 1536 2048 2560 3072 3584 4096 0 50 100 150 200 250 300 350 400 DIGITAL OUTPUT CODE DIGITAL OUTPUT CODE fIN (MHz) -THD, SFDR vs. ANALOG INPUT FREQUENCY (fCLK = 80MHz, AIN = -0.5dBFS) SNR, SINAD vs. ANALOG INPUT AMPLITUDE (fCLK = 80MHz, fIN = 70MHz) -THD, SFDR vs. ANALOG INPUT AMPLITUDE (fCLK = 80MHz, fIN = 70MHz) 85 SNR 90 65 80 70 65 -THD 55 -THD, SFDR (dB) SFDR SNR, SINAD (dB) 80 75 SINAD 45 35 25 50 50 100 150 200 250 300 350 400 fIN (MHz) SFDR 60 50 -THD 30 15 0 70 40 60 55 MAX12528 toc12 75 MAX12528 toc10 90 8 -60 -120 0 40 fIN1 ANALOG INPUT FREQUENCY (MHz) fCLK = 80MHz fIN = 2.1655273MHz 0.8 30 MAX12528 toc07 1.0 5 -40 -100 -120 0 fCLK = 65.00352MHz fIN1 = 172.50293MHz AIN1 = -6.99dBFS fIN2 = 177.40198MHz AIN2 = -7.01dBFS IM3 = -88.9dBc IMD = -82.2dBc -20 -100 -100 -110 -120 INL (LSB) fIN2 fIN1 -40 MAX12528 toc06 -20 0 MAX12528 toc11 AMPLITUDE (dBFS) -30 fCLK = 65.00352MHz fIN1 = 68.49889MHz fIN2 = 71.49832MHz AIN1 = -6.96dBFS AIN2 = -7.02dBFS IM3 = -92.3dBc IMD = -89.1dBc AMPLITUDE (dBFS) fIN 0 AMPLITUDE (dBFS) fCLK = 80MHz fIN = 174.9780273MHz AIN = -0.468dBFS SNR = 69.5dB SINAD = 67.9dB THD = -73.1dBc SFDR = 75dBc HD2 = -79.3dBc HD3 HD3 = -75dBc MAX12528 toc04 0 -10 -20 TWO-TONE IMD PLOT (16,384-POINT DATA RECORD) MAX12528 toc05 FFT PLOT (32,768-POINT DATA RECORD) -THD, SFDR (dBc) MAX12528 Dual, 80Msps, 12-Bit, IF/Baseband ADC 20 -55 -50 -45 -40 -35 -30 -25 -20 -15 -10 -5 AIN (dBFS) 0 -55 -50 -45 -40 -35 -30 -25 -20 -15 -10 -5 AIN (dBFS) _______________________________________________________________________________________ 0 Dual, 80Msps, 12-Bit, IF/Baseband ADC 45 SINAD 35 -THD 50 SINAD 65 60 40 55 25 30 15 50 20 -55 -50 -45 -40 -35 -30 -25 -20 -15 -10 -5 0 -55 -50 -45 -40 -35 -30 -25 -20 -15 -10 -5 10 0 20 30 40 50 60 70 AIN (dBFS) AIN (dBFS) fCLK (MHz) -THD, SFDR vs. CLOCK SPEED (fIN = 70MHz, AIN = -0.5dBFS) SNR, SINAD vs. CLOCK SPEED (fIN = 175MHz, AIN = -0.5dBFS) -THD, SFDR vs. CLOCK SPEED (fIN = 175MHz, AIN = -0.5dBFS) 70 75 SNR, SINAD (dB) 80 -THD 70 65 90 SFDR 85 80 MAX12528 toc18 85 SNR 80 65 -THD, SFDR (dBc) SFDR MAX12528 toc17 75 MAX12528 toc16 90 -THD, SFDR (dBc) 60 SNR 70 SNR, SINAD (dB) 70 55 75 MAX12528 toc14 SNR SFDR 80 -THD, SFDR (dBc) SNR, SINAD (dB) 65 90 MAX12528 toc13 75 SNR, SINAD vs. CLOCK SPEED (fIN = 70MHz, AIN = -0.5dBFS) -THD, SFDR vs. ANALOG INPUT AMPLITUDE (fCLK = 80MHz, fIN = 175MHz) MAX12528 toc15 SNR, SINAD vs. ANALOG INPUT AMPLITUDE (fCLK = 80MHz, fIN = 175MHz) SINAD 60 60 75 -THD 70 65 60 55 55 55 50 50 10 20 30 40 50 60 70 80 50 10 20 30 40 50 60 70 80 10 20 30 40 50 60 70 80 fCLK (MHz) fCLK (MHz) fCLK (MHz) SNR, SINAD vs. ANALOG SUPPLY VOLTAGE (fIN = 70MHz) -THD, SFDR vs. ANALOG SUPPLY VOLTAGE (fIN = 70MHz) SNR, SINAD vs. ANALOG SUPPLY VOLTAGE (fIN = 175MHz) 70 75 85 SFDR MAX12528 toc21 SNR MAX12528 toc20 90 MAX12528 toc19 75 SNR 70 SINAD 65 60 SNR, SINAD (dB) -THD, SFDR (dBc) SNR, SINAD (dB) 80 75 70 -THD 65 60 55 65 SINAD 60 55 55 50 50 3.0 3.1 3.2 3.3 VDD (V) 3.4 3.5 3.6 50 3.0 3.1 3.2 3.3 VDD (V) 3.4 3.5 3.6 3.0 3.1 3.2 3.3 3.4 3.5 3.6 VDD (V) _______________________________________________________________________________________ 9 MAX12528 Typical Operating Characteristics (continued) (VDD = 3.3V, OVDD = 2.0V, GND = 0, REFIN = REFOUT (internal reference mode), CL 5pF at digital outputs, AIN = -0.5dBFS, DIFFCLK/SECLK = OVDD, PD = GND, G/T = GND, fCLK = 80MHz (50% duty cycle), TA = +25C, unless otherwise noted.) Typical Operating Characteristics (continued) (VDD = 3.3V, OVDD = 2.0V, GND = 0, REFIN = REFOUT (internal reference mode), CL 5pF at digital outputs, AIN = -0.5dBFS, DIFFCLK/SECLK = OVDD, PD = GND, G/T = GND, fCLK = 80MHz (50% duty cycle), TA = +25C, unless otherwise noted.) SNR, SINAD vs. DIGITAL SUPPLY VOLTAGE (fIN = 70MHz) 70 SFDR SNR, SINAD (dB) 75 70 65 -THD 60 85 80 SINAD 65 60 70 65 -THD 60 55 55 55 50 50 3.0 3.1 3.2 3.3 3.4 3.5 50 1.5 3.6 1.8 2.1 2.4 2.7 3.0 3.3 3.6 1.5 1.8 2.1 2.4 2.7 3.0 3.3 3.6 VDD (V) OVDD (V) OVDD (V) SNR, SINAD vs. DIGITAL SUPPLY VOLTAGE (fIN = 175MHz) -THD, SFDR vs. DIGITAL POWER SUPPLY (fIN = 175MHz) PDISS, IVDD (ANALOG) vs. ANALOG SUPPLY VOLTAGE (fIN = 175MHz) 76 -THD, SFDR (dBc) 70 65 SINAD 60 55 1000 SFDR 72 68 -THD PDISS (ANALOG) 900 800 PDISS, IVDD (mW, mA) SNR MAX12528 toc26 80 MAX12528 toc25 75 SNR, SINAD (dB) SFDR 75 MAX12528 toc27 -THD, SFDR (dBc) 80 90 -THD, SFDR (dBc) 85 SNR MAX12528 toc24 75 MAX12528 toc22 90 -THD, SFDR vs. DIGITAL SUPPLY VOLTAGE (fIN = 70MHz) MAX12528 toc23 -THD, SFDR vs. ANALOG SUPPLY VOLTAGE (fIN = 175MHz) 700 600 500 400 IVDD 300 64 200 50 60 1.5 1.8 2.1 2.4 2.7 3.0 3.3 3.6 100 1.5 1.8 2.1 2.4 2.7 3.0 3.3 3.6 3.0 3.1 3.2 3.3 3.4 3.5 OVDD (V) OVDD (V) VDD (V) PDISS, IOVDD (DIGITAL) vs. DIGITAL SUPPLY VOLTAGE (fIN = 175MHz) SNR, SINAD vs. CLOCK DUTY CYCLE (fIN = 70MHz, AIN = -0.5dBFS) -THD, SFDR vs. CLOCK DUTY CYCLE (fIN = 70MHz, AIN = -0.5dBFS) 70 50 40 IOVDD 30 70 SNR, SINAD (dB) PDISS (DIGITAL) 60 20 65 SINAD 60 55 1.8 2.1 2.4 2.7 OVDD (V) 10 SINGLE-ENDED CLOCK DRIVE 50 1.5 3.0 3.3 3.6 85 SFDR 80 75 70 -THD 65 10 0 90 3.6 MAX12528 toc30 80 SNR -THD, SFDR (dBc) 90 MAX12528 toc29 75 MAX12528 toc28 100 PDISS, IOVDD (mW, mA) MAX12528 Dual, 80Msps, 12-Bit, IF/Baseband ADC 25 35 45 55 CLOCK DUTY CYCLE (%) 60 65 75 SINGLE-ENDED CLOCK DRIVE 25 35 45 55 CLOCK DUTY CYCLE (%) ______________________________________________________________________________________ 65 75 Dual, 80Msps, 12-Bit, IF/Baseband ADC SNR, SINAD vs. TEMPERATURE (fIN = 175MHz, AIN = -0.5dBFS) 85 -THD, SFDR (dBc) 70 68 66 SINAD 64 MAX12528 toc32 SNR SNR, SINAD (dB) 90 MAX12528 toc31 72 -THD, SFDR vs. TEMPERATURE (fIN = 175MHz, AIN = -0.5dBFS) 80 SFDR 75 70 -THD 62 65 60 60 -40 -15 10 35 60 85 -40 -15 TEMPERATURE (C) GAIN ERROR vs. TEMPERATURE (VREFIN = 2.048V) 35 60 85 OFFSET ERROR vs. TEMPERATURE 1.5 0.15 OFFSET ERROR (%FSR) 1.0 0.5 0 -0.5 -1.0 -1.5 MAX12528 toc34 0.20 MAX12528 toc33 2.0 GAIN ERROR (%FSR) 10 TEMPERATURE (C) 0.10 0.05 0 -0.05 -0.10 -0.15 -2.0 -40 -15 10 35 TEMPERATURE (C) 60 85 -0.20 -40 -15 10 35 TEMPERATURE (C) 60 85 ______________________________________________________________________________________ 11 MAX12528 Typical Operating Characteristics (continued) (VDD = 3.3V, OVDD = 2.0V, GND = 0, REFIN = REFOUT (internal reference mode), CL 5pF at digital outputs, AIN = -0.5dBFS, DIFFCLK/SECLK = OVDD, PD = GND, G/T = GND, fCLK = 80MHz (50% duty cycle), TA = +25C, unless otherwise noted.) MAX12528 Dual, 80Msps, 12-Bit, IF/Baseband ADC Pin Description PIN NAME 1, 4, 5, 9, 13, 14, 17 GND Converter Ground. Connect all ground pins and the exposed paddle (EP) together. 2 INAP Channel A Positive Analog Input 3 INAN Channel A Negative Analog Input 6 COMA Channel A Common-Mode Voltage I/O. Bypass COMA to GND with a 0.1F capacitor. REFAP Channel A Positive Reference I/O. Channel A conversion range is 2/3 x (VREFAP - VREFAN). Bypass REFAP with a 0.1F capacitor to GND. Connect a 10F and a 1F bypass capacitor between REFAP and REFAN. Place the 1F REFAP-to-REFAN capacitor as close to the device as possible on the same side of the PC board. REFAN Channel A Negative Reference I/O. Channel A conversion range is 2/3 x (VREFAP - VREFAN). Bypass REFAN with a 0.1F capacitor to GND. Connect a 10F and a 1F bypass capacitor between REFAP and REFAN. Place the 1F REFAP-to-REFAN capacitor as close to the device as possible on the same side of the PC board. REFBN Channel B Negative Reference I/O. Channel B conversion range is 2/3 x (VREFBP - VREFBN). Bypass REFBN with a 0.1F capacitor to GND. Connect a 10F and a 1F bypass capacitor between REFBP and REFBN. Place the 1F REFBP-to-REFBN capacitor as close to the device as possible on the same side of the PC board. 11 REFBP Channel B Positive Reference I/O. Channel B conversion range is 2/3 x (VREFBP - VREFBN). Bypass REFBP with a 0.1F capacitor to GND. Connect a 10F and a 1F bypass capacitor between REFBP and REFBN. Place the 1F REFBP-to-REFBN capacitor as close to the device as possible on the same side of the PC board. 12 COMB 15 INBN 16 INBP 7 8 10 FUNCTION Channel A Common-Mode Voltage I/O. Bypass COMB to GND with a 0.1F capacitor. Channel B Negative Analog Input Channel B Positive Analog Input 18 DIFFCLK/ SECLK 19 CLKN 20 CLKP 21 DIV2 Differential/Single-Ended Input Clock Drive. This input selects between single-ended or differential clock input drives. DIFFCLK/SECLK = GND: Selects single-ended clock input drive. DIFFCLK/SECLK = OVDD: Selects differential clock input drive. Negative Clock Input. In differential clock input mode (DIFFCLK/SECLK = OVDD), connect a differential clock signal between CLKP and CLKN. In single-ended clock mode (DIFFCLK/SECLK = GND), apply the clock signal to CLKP and connect CLKN to GND. Positive Clock Input. In differential clock input mode (DIFFCLK/SECLK = OVDD), connect a differential clock signal between CLKP and CLKN. In single-ended clock mode (DIFFCLK/SECLK = GND), apply the single-ended clock signal to CLKP and connect CLKN to GND. Divide-by-Two Clock-Divider Digital Control Input. See Table 2 for details. 22 DIV4 Divide-by-Four Clock-Divider Digital Control Input. See Table 2 for details. 23-26, 61, 62, 63 VDD Analog Power Input. Connect VDD to a 3.15V to 3.60V power supply. Bypass VDD to GND with a parallel capacitor combination of 10F and 0.1F. Connect all VDD pins to the same potential. 27, 43, 60 OVDD Output-Driver Power Input. Connect OVDD to a 1.7V to VDD power supply. Bypass OVDD to GND with a parallel capacitor combination of 10F and 0.1F. 28, 29, 45, 46 N.C. 12 No Connection ______________________________________________________________________________________ Dual, 80Msps, 12-Bit, IF/Baseband ADC PIN NAME FUNCTION 30 D0B Channel B CMOS Digital Output, Bit 0 (LSB) 31 D1B Channel B CMOS Digital Output, Bit 1 32 D2B Channel B CMOS Digital Output, Bit 2 33 D3B Channel B CMOS Digital Output, Bit 3 34 D4B Channel B CMOS Digital Output, Bit 4 35 D5B Channel B CMOS Digital Output, Bit 5 36 D6B Channel B CMOS Digital Output, Bit 6 37 D7B Channel B CMOS Digital Output, Bit 7 38 D8B Channel B CMOS Digital Output, Bit 8 39 D9B Channel B CMOS Digital Output, Bit 9 40 D10B Channel B CMOS Digital Output, Bit 10 41 D11B Channel B CMOS Digital Output, Bit 11 (MSB) 42 DORB Channel B Data Out-of-Range Indicator. The DORB digital output indicates when the channel B analog input voltage is out of range. DORB = 1: Digital outputs exceed full-scale range. DORB = 0: Digital outputs are within full-scale range. 44 DAV 47 D0A Data-Valid Digital Output. The rising edge of DAV indicates that data is present on the digital outputs. The MAX12528 evaluation kit (MAX12528 EV kit) utilizes DAV to latch data into any external back-end digital logic. Channel A CMOS Digital Output, Bit 0 (LSB) 48 D1A Channel A CMOS Digital Output, Bit 1 49 D2A Channel A CMOS Digital Output, Bit 2 50 D3A Channel A CMOS Digital Output, Bit 3 51 D4A Channel A CMOS Digital Output, Bit 4 52 D5A Channel A CMOS Digital Output, Bit 5 53 D6A Channel A CMOS Digital Output, Bit 6 54 D7A Channel A CMOS Digital Output, Bit 7 55 D8A Channel A CMOS Digital Output, Bit 8 56 D9A Channel A CMOS Digital Output, Bit 9 57 D10A Channel A CMOS Digital Output, Bit 10 58 D11A 59 DORA 64 G/T Channel A CMOS Digital Output, Bit 11 (MSB) Channel A Data Out-of-Range Indicator. The DORA digital output indicates when the channel A analog input voltage is out of range. DORA = 1: Digital outputs exceed full-scale range. DORA = 0: Digital outputs are within full-scale range. Output Format Select Digital Input. G/T = GND: Two's-complement output format selected. G/T = OVDD: Gray-code output format selected. 65 PD Power-Down Digital Input. PD = GND: ADCs are fully operational. PD = OVDD: ADCs are powered down. ______________________________________________________________________________________ 13 MAX12528 Pin Description (continued) Dual, 80Msps, 12-Bit, IF/Baseband ADC MAX12528 Pin Description (continued) PIN NAME 66 SHREF 67 REFOUT 68 REFIN -- EP FUNCTION Shared Reference Digital Input. SHREF = VDD: Shared reference enabled. SHREF = GND: Shared reference disabled. When sharing the reference, externally connect REFAP and REFBP together to ensure that VREFAP equals VREFBP. Similarly, when sharing the reference, externally connect REFAN to REFBN together to ensure that VREFAN = VREFBN. Internal Reference Voltage Output. The REFOUT output voltage is 2.048V and REFOUT can deliver 1mA. For internal reference operation, connect REFOUT directly to REFIN or use a resistive divider from REFOUT to set the voltage at REFIN. Bypass REFOUT to GND with a 0.1F capacitor. For external reference operation, REFOUT is not required and must be bypassed to GND with a 0.1F capacitor. Single-Ended Reference Analog Input. For internal reference and buffered external reference operation, apply a 0.7V to 2.3V DC reference voltage to REFIN. Bypass REFIN to GND with a 4.7F capacitor. Within its specified operating voltage, REFIN has a >50M input impedance, and the differential reference voltage (VREF_P - VREF_N) is generated from REFIN. For unbuffered external reference operation, connect REFIN to GND. In this mode REF_P, REF_N, and COM_ are high-impedance inputs that accept the external reference voltages. Exposed Paddle. EP is internally connected to GND. Externally connect EP to GND to achieve specified dynamic performance. + MAX12528 x2 - FLASH ADC DAC IN_P STAGE 1 STAGE 2 STAGE 9 IN_N STAGE 10 END OF PIPELINE DIGITAL ERROR CORRECTION D0_ THROUGH D11_ Figure 1. Pipeline Architecture--Stage Blocks Detailed Description The MAX12528 uses a 10-stage, fully differential, pipelined architecture (Figure 1) that allows for highspeed conversion while minimizing power consumption. Samples taken at the inputs move progressively through the pipeline stages every half clock cycle. From input to output the total latency is 8 clock cycles. 14 Each pipeline converter stage converts its input voltage to a digital output code. At every stage, except the last, the error between the input voltage and the digital output code is multiplied and passed along to the next pipeline stage. Digital error correction compensates for ADC comparator offsets in each pipeline stage and ensures no missing codes. Figure 2 shows the MAX12528 functional diagram. ______________________________________________________________________________________ Dual, 80Msps, 12-Bit, IF/Baseband ADC MAX12528 CLOCK INAP INAN REFAP COMA REFAN 12-BIT PIPELINE ADC CHANNEL A REFERENCE SYSTEM DIGITAL ERROR CORRECTION DATA FORMAT OUTPUT DRIVERS D0A TO D11A DORA MAX12528 G/T REFIN INTERNAL REFERENCE GENERATOR REFOUT DAV SHREF REFBP COMB REFBN INBP INBN OVDD CHANNEL B REFERENCE SYSTEM 12-BIT PIPELINE ADC DIGITAL ERROR CORRECTION DATA FORMAT OUTPUT DRIVERS D0B TO D11B DORB CLOCK VDD DIFFCLK/SECLK CLOCK CLKP CLKN DIV2 DIV4 CLOCK DIVIDER DUTY-CYCLE EQUALIZER POWER CONTROL AND BIAS CIRCUITS PD GND Figure 2. Functional Diagram ______________________________________________________________________________________ 15 MAX12528 Dual, 80Msps, 12-Bit, IF/Baseband ADC Table 1. Reference Modes BOND WIRE INDUCTANCE 1.5nH VDD MAX12528 IN_P CPAR 2pF BOND WIRE INDUCTANCE 1.5nH *CSAMPLE 4.5pF VDD VREFIN IN_N CPAR 2pF *CSAMPLE 4.5pF 0.7V to 2.3V SAMPLING CLOCK *THE EFFECTIVE RESISTANCE OF THE SWITCHED SAMPLING CAPACITORS IS: RIN = 1 fCLK x CSAMPLE Figure 3. Internal T/H Circuit Analog Inputs and Input Track-and-Hold (T/H) Amplifier Figure 3 displays a simplified functional diagram of the input T/H circuit. This input T/H circuit allows for high analog input frequencies of 175MHz and beyond and supports a VDD / 2 common-mode input voltage. The MAX12528 sampling clock controls the switchedcapacitor input T/H architecture (Figure 3) allowing the analog input signals to be stored as charge on the sampling capacitors. These switches are closed (track mode) when the sampling clock is high and open (hold mode) when the sampling clock is low (Figure 4). The analog input signal source must be able to provide the dynamic currents necessary to charge and discharge the sampling capacitors. To avoid signal degradation, these capacitors must be charged to one-half LSB accuracy within one-half of a clock cycle. The analog input of the MAX12528 supports differential or singleended input drive. For optimum performance with differential inputs, balance the input impedance of IN_P and IN_N and set the common-mode voltage to midsupply (VDD / 2). The MAX12528 provides the optimum common-mode voltage of VDD / 2 through the COM output when operating in internal reference mode and buffered external reference mode. This COM output voltage can be used to bias the input network as shown in Figures 9, 10, and 11. Reference Output An internal bandgap reference is the basis for all the internal voltages and bias currents used in the 16 REFERENCE MODE Internal Reference Mode. REFIN is driven by REFOUT either through a 35% VREFOUT direct short or a resistive divider. to 100% VCOM_ = VDD / 2 VREFOUT VREF_P = VDD / 2 + 3/8 x VREFIN VREF_N = VDD / 2 - 3/8 x VREFIN <0.5V Buffered External Reference Mode. An external 0.7V to 2.3V reference voltage is applied to REFIN. VCOM_ = VDD / 2 VREF_P = VDD / 2 + 3/8 x VREFIN VREF_N = VDD / 2 - 3/8 x VREFIN Unbuffered External Reference Mode. REF_P, REF_N, and COM_ are driven by external reference sources. The full-scale analog input range is (VREF_P - VREF_N) x 2/3. MAX12528. The power-down logic input (PD) enables and disables the reference circuit. REFOUT has approximately 17k to GND when the MAX12528 is powered down. The reference circuit requires 10ms to power up and settle to its final value when power is applied to the MAX12528 or when PD transitions from high to low. The internal bandgap reference produces a buffered reference voltage of 2.048V 1% at the REFOUT pin with a 50ppm/C temperature coefficient. Connect an external 0.1F bypass capacitor from REFOUT to GND for stability. REFOUT sources up to 1mA and sinks up to 0.1mA for external circuits with a 35mV/mA load regulation. Short-circuit protection limits IREFOUT to a 2.1mA source current when shorted to GND and a 0.24mA sink current when shorted to VDD. Similar to REFOUT, REFIN should be bypassed with a 4.7F capacitor to GND. Reference Configurations The MAX12528 full-scale analog input range is 2/3 x VREF with a VDD / 2 0.5V common-mode input range. VREF is the voltage difference between REFAP (REFBP) and REFAN (REFBN). The MAX12528 provides three modes of reference operation. The voltage at REFIN (VREFIN) selects the reference operation mode (Table 1). Connect REFOUT to REFIN either with a direct short or through a resistive divider to enter internal reference mode. COM_, REF_P, and REF_N are low-impedance outputs with VCOM_ = VDD / 2, VREFP = VDD / 2 + 3/8 x VREFIN, and VREF_N = VDD / 2 - 3/8 x VREFIN. Bypass REF_P, REF_N, and COM_ each with a 0.1F capacitor to GND. Bypass REF_P to REF_N with a 10F capacitor. ______________________________________________________________________________________ Dual, 80Msps, 12-Bit, IF/Baseband ADC Clock Duty-Cycle Equalizer The MAX12528 has an internal clock duty-cycle equalizer, which makes the converter insensitive to the duty cycle of the signal applied to CLKP and CLKN. The converters allow clock duty-cycle variations from 25% to 75% without negatively impacting the dynamic performance. The clock duty-cycle equalizer uses a delay-locked loop (DLL) to create internal timing signals that are duty-cycle independent. Due to this DLL, the MAX12528 requires approximately 100 clock cycles to acquire and lock to new clock frequencies. Clock Input and Clock Control Lines The MAX12528 accepts both differential and singleended clock inputs with a wide 25% to 75% input clock duty cycle. For single-ended clock input operation, connect DIFFCLK/SECLK and CLKN to GND. Apply an external single-ended clock signal to CLKP. To reduce clock jitter, the external single-ended clock must have sharp falling edges. For differential clock input operation, connect DIFFCLK/SECLK to OV DD . Apply an external differential clock signal to CLKP and CLKN. Consider the clock input as an analog input and route it away from any other analog inputs and digital signal lines. CLKP and CLKN enter high impedance when the MAX12528 is powered down (Figure 4). Low clock jitter is required for the specified SNR performance of the MAX12528. The analog inputs are sampled on the falling (rising) edge of CLKP (CLKN), requiring this edge to have the lowest possible jitter. Jitter limits the maximum SNR performance of any ADC according to the following relationship: 1 SNR = 20 x log 2 x x f x t IN J where fIN represents the analog input frequency and tJ is the total system clock jitter. Clock jitter is especially critical for undersampling applications. For instance, assuming that clock jitter is the only noise source, to obtain the specified 69.8dB of SNR with an input frequency of 175MHz the system must have less than 0.29ps of clock jitter. However, in reality there are other noise sources such as thermal noise and quantization noise that contribute to the system noise requiring the clock jitter to be less than 0.14ps to obtain the specified 69.8dB of SNR at 175MHz. Clock-Divider Control Inputs (DIV2, DIV4) The MAX12528 features three different modes of sampling/clock operation (see Table 2). Pulling both control lines low, the clock-divider function is disabled and the converters sample at full clock speed. Pulling DIV4 low and DIV2 high enables the divide-by-two feature, which sets the sampling speed to one-half the selected clock frequency. In divide-by-four mode, the converter sampling speed is set to one-fourth the clock speed of the MAX12528. Divide-by-four mode is achieved by applying a high level to DIV4 and a low level to DIV2. The option to select either one-half or one-fourth of the clock speed for ______________________________________________________________________________________ 17 MAX12528 Bypass REFIN and REFOUT to GND with a 0.1F capacitor. The REFIN input impedance is very large (>50M). When driving REFIN through a resistive divider, use resistances 10k to avoid loading REFOUT. Buffered external reference mode is virtually identical to the internal reference mode except that the reference source is derived from an external reference and not the MAX12528's internal bandgap reference. In buffered external reference mode, apply a stable reference voltage source between 0.7V to 2.3V at REFIN. Pins COM_, REF_P, and REF_N are low-impedance outputs with VCOM_ = VDD / 2, VREF_P = VDD / 2 + 3/8 x VREFIN, and VREF_N = VDD / 2 - 3/8 x VREFIN. Bypass REF_P, REF_N, and COM_ each with a 0.1F capacitor to GND. Bypass REF_P to REF_N with a 10F capacitor. Connect REFIN to GND to enter unbuffered external reference mode. Connecting REFIN to GND deactivates the on-chip reference buffers for COM_, REF_P, and REF_N. With their buffers deactivated, COM_, REF_P, and REF_N become high-impedance inputs and must be driven with separate, external reference sources. Drive VCOM_ to VDD / 2 5%, and drive REF_P and REF_N so VCOM_ = (VREF_P_ + VREF_N_) / 2. The analog input range is (V REF_P_ - V REF_N ) x 2/3. Bypass REF_P, REF_N, and COM_ each with a 0.1F capacitor to GND. Bypass REF_P to REF_N with a 10F capacitor. For all reference modes, bypass REFOUT with a 0.1F and REFIN with a 4.7F capacitor to GND. The MAX12528 also features a shared reference mode, in which the user can achieve better channel-to-channel matching. When sharing the reference (SHREF = VDD), externally connect REFAP and REFBP together to ensure that VREFAP = VREFBP. Similarly, when sharing the reference, externally connect REFAN to REFBN together to ensure that VREFAN = VREFBN. Connect SHREF to GND to disable the shared reference mode of the MAX12528. In this independent reference mode, a better channel-to-channel isolation is achieved. For detailed circuit suggestions and how to drive the ADC in buffered/unbuffered external reference mode, see the Applications Information section. MAX12528 Dual, 80Msps, 12-Bit, IF/Baseband ADC Table 2. Clock-Divider Control Inputs VDD S1H MAX12528 10k DIV4 DIV2 0 0 Clock Divider Disabled fSAMPLE = fCLK 0 1 Divide-by-Two Clock Divider fSAMPLE = fCLK / 2 1 0 Divide-by-Four Clock Divider fSAMPLE = fCLK / 4 1 1 Not Allowed CLKP 10k DUTY-CYCLE EQUALIZER S2H S1L 10k cuitry can be latched with the rising edge of the conversion clock (CLKP - CLKN). CLKN Data-Valid Output DAV is a single-ended version of the input clock that is compensated to correct for any input clock duty-cycle variations. The MAX12528 output data changes on the falling edge of DAV, and DAV rises once the output data is valid. The falling edge of DAV is synchronized to have a 5.4ns delay from the falling edge of the input clock. Output data at D0A/B-D11A/B and DORA/B are valid from 7ns before the rising edge of DAV to 7ns after the rising edge of DAV. 10k S2L GND SWITCHES S1_ AND S2_ ARE OPEN DURING POWER-DOWN MAKING CLKP AND CLKN HIGH IMPEDANCE. SWITCHES S2_ ARE OPEN IN SINGLE-ENDED CLOCK MODE. Figure 4. Simplified Clock Input Circuit sampling provides design flexibility, relaxes clock requirements, and can minimize clock jitter. DAV enters high impedance when the MAX12528 is powered down (PD = OV DD ). DAV enters its highimpedance state 10ns after the rising edge of PD and becomes active again 10ns after PD transitions low. DAV is capable of sinking and sourcing 600A and has three times the driving capabilities of D0A/B-D11A/B and DORA/B. DAV is typically used to latch the MAX12528 output data into an external digital back-end circuit. Keep the capacitive load on DAV as low as possible (<15pF) to avoid large digital currents feeding back into the analog portion of the MAX12528, thereby degrading its dynamic performance. Buffering DAV System Timing Requirements Figure 5 shows the timing relationship between the clock, analog inputs, DAV indicator, DOR_ indicators, and the resulting output data. The analog input is sampled on the falling (rising) edge of CLKP (CLKN) and the resulting data appears at the digital outputs 8 clock cycles later. The DAV indicator is synchronized with the digital output and optimized for use in latching data into digital back-end circuitry. Alternatively, digital back-end cirN+4 DIFFERENTIAL ANALOG INPUT (IN_P-IN_N) (VREF_P - VREF_N) x 2/3 N+5 N+3 N-3 N-2 N-1 N N+1 FUNCTION N+6 N +2 N+7 N+9 N+8 (VREF_N - VREF_P) x 2/3 tAD CLKN CLKP tDAV tCL tCH DAV tSETUP D0_-D11_ tHOLD N-3 8.0 CLOCK-CYCLE DATA LATENCY N-2 N-1 N N+1 N+2 N+3 N+4 N+5 N+6 N+7 tSETUP DOR Figure 5. System Timing Diagram 18 ______________________________________________________________________________________ N+8 N+9 tHOLD Dual, 80Msps, 12-Bit, IF/Baseband ADC Data Out-of-Range Indicator The DORA and DORB digital outputs indicate when the analog input voltage is out of range. When DOR_ is high, the analog input is out of range. When DOR_ is low, the analog input is within range. The valid differential input range is from (V REF_P - V REF_N ) x 2/3 to (V REF_N VREF_P) x 2/3. Signals outside of this valid differential range cause DOR_ to assert high as shown in Table 1. DOR is synchronized with DAV and transitions along with the output data D11-D0. There is an 8 clock-cycle latency in the DOR function as is with the output data (Figure 5). DOR_ is high impedance when the MAX12528 is in power-down (PD = high). DOR_ enters a high-impedance state within 10ns after the rising edge of PD and becomes active 10ns after PD's falling edge. Digital Output Data and Output Format Selection The MAX12528 provides two 12-bit, parallel, tri-state output buses. D0A/B-D11A/B and DORA/B update on the falling edge of DAV and are valid on the rising edge of DAV. The MAX12528 output data format is either Gray code or two's complement depending on the logic input G/T. With G/T high, the output data format is Gray code. With G/T low, the output data format is set to two's complement. See Figure 8 for a binary-to-Gray and Gray-tobinary code conversion example. The following equations, Table 3, Figure 6, and Figure 7 define the relationship between the digital output and the analog input. Gray Code (G/T = 1): VIN_P - VIN_N = 2/3 x (VREF_P - VREF_N) x 2 x (CODE10 - 2048) / 4096 Two's Complement (G/T = 0): VIN_P - VIN_N = 2/3 x (VREF_P - VREF_N) x 2 x CODE10 / 4096 where CODE10 is the decimal equivalent of the digital output code as shown in Table 3. Table 3. Output Codes vs. Input Voltage GRAY-CODE OUTPUT CODE (G/T = 1) BINARY D11A-D0A D11B-D0B TWO'S COMPLEMENT OUTPUT CODE (G/T = 0) DECIMAL HEXADECIMAL EQUIVALENT EQUIVALENT OF DOR OF D11A-D0A D11A-D0A D11B-D0B D11B-D0B (CODE10) BINARY D11A-D0A D11B-D0B DECIMAL VIN_P - VIN_N HEXADECIMAL EQUIVALENT VREF_P = 2.418V EQUIVALENT OF VREF_N = 0.882V DOR OF D11A-D0A D11A-D0A D11B-D0B D11B-D0B (CODE10) 1000 0000 0000 1 0x800 +4095 0111 1111 1111 1 0x7FF +2047 >+1.0235V (DATA OUT OF RANGE) 1000 0000 0000 0 0x800 +4095 0111 1111 1111 0 0x7FF +2047 +1.0235V 1000 0000 0001 0 0x801 +4094 0111 1111 1110 0 0x7FE +2046 +1.0230V 1100 0000 0011 0 0xC03 +2050 0000 0000 0010 0 0x002 +2 +0.0010V 1100 0000 0001 0 0xC01 +2049 0000 0000 0001 0 0x001 +1 +0.0005V 1100 0000 0000 0 0xC00 +2048 0000 0000 0000 0 0x000 0 +0.0000V 0100 0000 0000 0 0x400 +2047 1111 1111 1111 0 0xFFF -1 -0.0005V 0100 0000 0001 0 0x401 +2046 1111 1111 1110 0 0xFFE -2 -0.0010V 0000 0000 0001 0 0x001 +1 1000 0000 0001 0 0x801 -2047 -1.0235V 0000 0000 0000 0 0x000 0 1000 0000 0000 0 0x800 -2048 -1.0240V -2048 <-1.0240V (DATA OUT OF RANGE) 0000 0000 0000 1 0x000 0 1000 0000 0000 1 0x800 ______________________________________________________________________________________ 19 MAX12528 externally isolates it from heavy capacitive loads. Refer to the MAX12557 EV kit schematic for recommendations of how to drive the DAV signal through an external buffer. MAX12528 Dual, 80Msps, 12-Bit, IF/Baseband ADC 1 LSB = 4/3 x (VREFP - VREFN) / 4096 2/3 x (VREFP - VREFN) 2/3 x (VREFP - VREFN) 0x7FF 0x7FE 0x800 0x801 0x7FD 0x803 GRAY OUTPUT CODE (LSB) TWO'S-COMPLEMENT OUTPUT CODE (LSB) 2/3 x (VREFP - VREFN) 1 LSB = 4/3 x (VREFP - VREFN) / 4096 0x001 0x000 0xFFF 0xC01 0xC00 0xC00 0x803 0x802 0x002 0x003 0x801 0x800 0x001 0x000 -2047 -2045 -1 0 +1 +2045 +2047 DIFFERENTIAL INPUT VOLTAGE (LSB) 2/3 x (VREFP - VREFN) -2047 -2045 -1 0 +1 +2045 +2047 DIFFERENTIAL INPUT VOLTAGE (LSB) Figure 6. Two's-Complement Transfer Function (G/T = 0) Figure 7. Gray-Code Transfer Function (G/T = 1) The digital outputs D0A/B-D11A/B are high impedance when the MAX12528 is in power-down (PD = 1) mode. D0A/B-D11A/B enter this state 10ns after the rising edge of PD and become active again 10ns after PD transitions low. Keep the capacitive load on the MAX12528 digital outputs D0A/B-D11A/B as low as possible (<15pF) to avoid large digital currents feeding back into the analog portion of the MAX12528 and degrading its dynamic performance. Adding external digital buffers on the digital outputs helps isolate the MAX12528 from heavy capacitive loads. To improve the dynamic performance of the MAX12528, add 220 resistors in series with the digital outputs close to the MAX12528. Refer to the MAX12557 EV kit schematic for guidelines of how to drive the digital outputs through 220 series resistors and external digital output buffers. In power-down mode all internal circuits are off, the analog supply current reduces to less than 100A, and the digital supply current reduces to less than 1A. The following list shows the state of the analog inputs and digital outputs in power-down mode: Power-Down Input 6) CLKP and CLKN clock inputs enter a high-impedance state (Figure 4). The MAX12528 has two power modes that are controlled with a power-down digital input (PD). With PD low, the MAX12528 is in its normal operating mode. With PD high, the MAX12528 is in power-down mode. The power-down mode allows the MAX12528 to efficiently use power by transitioning to a low-power state when conversions are not required. Additionally, the MAX12528 parallel output bus goes high-impedance in power-down mode, allowing other devices on the bus to be accessed. 20 1) INAP/B and INAN/B analog inputs are disconnected from the internal input amplifier (Figure 3). 2) REFOUT has approximately 17k to GND. 3) REFAP/B, COMA/B, and REFAN/B enter a highimpedance state with respect to VDD and GND, but there is an internal 4k resistor between REFAP/B and COMA/B, as well as an internal 4k resistor between REFAN/B and COMA/B. 4) D0A-D11A, D0B-D11B, DORA, and DORB enter a high-impedance state. 5) DAV enters a high-impedance state. The wake-up time from power-down mode is dominated by the time required to charge the capacitors at REF_P, REF_N, and COM. In internal reference mode and buffered external reference mode the wake-up time is typically 10ms. When operating in the unbuffered external reference mode the wake-up time is dependent on the external reference drivers. ______________________________________________________________________________________ Dual, 80Msps, 12-Bit, IF/Baseband ADC GRAY-TO-BINARY CODE CONVERSION 1) THE MOST SIGNIFICANT BINARY BIT IS THE SAME AS THE MOST SIGNIFICANT GRAY-CODE BIT. D11 0 D7 1 1 1 0 D3 1 0 0 1 D0 1 0 0 0 BIT POSITION D11 BINARY 0 GRAY CODE 0 2) SUBSEQUENT GRAY-CODE BITS ARE FOUND ACCORDING TO THE FOLLOWING EQUATION: 1 0 0 1 D3 1 1 GRAYX = BINARYX + BINARYX + 1 BINARY10 = 0 + 1 GRAY10 = 1 BINARY10 = 1 D7 1 1 0 D3 1 0 1 0 GRAY CODE BINARYX = BINARYX+1 + GRAYX BINARY10 = BINARY11 + GRAY10 1 0 WHERE + IS THE EXCLUSIVE OR FUNCTION (SEE TRUTH TABLE BELOW) AND X IS THE BIT POSITION: GRAY10 = 1 + 0 + 1 BIT POSITION BINARY GRAY10 = BINARY10 + BINARY11 D11 0 D0 2) SUBSEQUENT BINARY BITS ARE FOUND ACCORDING TO THE FOLLOWING EQUATION: WHERE + IS THE EXCLUSIVE OR FUNCTION (SEE TRUTH TABLE BELOW) AND X IS THE BIT POSITION: 0 D7 MAX12528 BINARY-TO-GRAY CODE CONVERSION 1) THE MOST SIGNIFICANT GRAY-CODE BIT IS THE SAME AS THE MOST SIGNIFICANT BINARY BIT. 0 1 D0 1 0 0 D11 BIT POSITION BINARY 0 GRAY CODE 0 D7 1 0 0 1 D3 1 1 0 1 D0 0 1 0 BIT POSITION GRAY CODE + 0 1 3) REPEAT STEP 2 UNTIL COMPLETE: BINARY 1 3) REPEAT STEP 2 UNTIL COMPLETE: GRAY9 = BINARY9 + BINARY10 BINARY9 = BINARY10 + GRAY9 GRAY9 = 1 + 1 BINARY9 = 1 + 0 GRAY9 = 0 BINARY9 = 1 D11 0 1 0 1 D7 + 1 1 0 D3 1 0 0 1 D0 1 0 0 BIT POSITION D11 BINARY 0 1 GRAY CODE 0 1 D7 0 0 1 D3 1 1 0 1 D0 0 1 0 BIT POSITION GRAY CODE + 0 4) THE FINAL GRAY-CODE CONVERSION IS: D11 D7 1 BINARY 4) THE FINAL BINARY CONVERSION IS: D3 D0 BIT POSITION D11 D7 D3 D0 BIT POSITION 0 1 1 1 0 1 0 0 1 1 0 0 BINARY 0 1 0 0 1 1 1 0 1 0 1 0 GRAY CODE 0 1 0 0 1 1 1 0 1 0 1 0 GRAY CODE 0 1 1 1 0 1 0 0 1 1 0 0 BINARY EXCLUSIVE OR TRUTH TABLE FIGURE 8 SHOWS THE GRAY-TO-BINARY AND BINARY-TO-GRAY CODE CONVERSION IN OFFSET BINARY FORMAT. THE OUTPUT FORMAT OF THE MAX12528 IS TWO'S-COMPLEMENT BINARY, HENCE EACH MSB OF THE TWO'S-COMPLEMENT OUTPUT CODE MUST BE INSERTED TO REFLECT TRUE OFFSET BINARY FORMAT. A B 0 0 1 1 0 1 0 1 Y = A + B 0 1 1 0 Figure 8. Binary-to-Gray and Gray-to-Binary Code Conversion ______________________________________________________________________________________ 21 MAX12528 Dual, 80Msps, 12-Bit, IF/Baseband ADC overall distortion. The configuration of Figure 9 is good for frequencies up to Nyquist (fCLK / 2). Applications Information Using Transformer Coupling The circuit of Figure 10 converts a single-ended input signal to fully differential just as Figure 9. However, Figure 10 utilizes an additional transformer to improve the common-mode rejection allowing high-frequency signals beyond the Nyquist frequency. A set of 75 and 113 termination resistors provide an equivalent 50 termination to the signal source. The second set of termination resistors connects to COM_ providing the correct input common-mode voltage. Two 0 resistors in series with the analog inputs allow high IF input frequencies. These 0 resistors can be replaced with lowvalue resistors to limit the input bandwidth. In general, the MAX12528 provides better SFDR and THD with fully differential input signals than singleended input drive, especially for input frequencies above 125MHz. In differential input mode, even-order harmonics are lower as both inputs are balanced, and each of the ADC inputs only requires half the signal swing compared to single-ended input mode. An RF transformer (Figure 9) provides an excellent solution to convert a single-ended input source signal to a fully differential signal, required by the MAX12528 for optimum performance. Connecting the center tap of the transformer to COM provides a VDD / 2 DC level shift to the input. 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 Single-Ended AC-Coupled Input Signal Figure 11 shows an AC-coupled, single-ended input application. The MAX4108 provides high speed, high bandwidth, low noise, and low distortion to maintain the input signal integrity. 24.9 IN_P 5.6pF 0.1F VIN VIN 1 6 T1 N.C. 5 0.1F MAX12528 0 IN_P MAX4108 5.6pF 2 100 COM_ 24.9 MAX12528 0.1F 3 COM_ 4 0.1F MINICIRCUITS TT1-6 OR T1-1T 100 24.9 24.9 IN_N IN_N 5.6pF 5.6pF Figure 11. Single-Ended, AC-Coupled Input Drive Figure 9. Transformer-Coupled Input Drive for Input Frequencies Up to Nyquist 0* IN_P 0.1F 1 VIN N.C. 5 T1 6 2 1 75 1% N.C. N.C. 5 T2 5.6pF 6 2 113 0.5% MAX12528 COM_ N.C. 0.1F 3 4 MINICIRCUITS ADT1-1WT 75 1% 3 4 MINICIRCUITS ADT1-1WT 113 0.5% 0* IN_N 5.6pF *0 RESISTORS CAN BE REPLACED WITH LOW-VALUE RESISTORS TO LIMIT THE INPUT BANDWIDTH. Figure 10. Transformer-Coupled Input Drive for Input Frequencies beyond Nyquist 22 ______________________________________________________________________________________ Dual, 80Msps, 12-Bit, IF/Baseband ADC MAX12528 3.3V 0.1F 2.2F VDD REF_P REFIN 0.1F 0.1F 1 5 16.2k 3 MAX6029 (EUK21) 0.1F 1 47 300F 6V 0.1F REF_N MAX4230 4 10F MAX12528 5 1F 2.048V 0.1F 2 2 COM_ REFOUT 1.47k GND 0.1F 0.1F NOTE: ONE FRONT-END REFERENCE CIRCUIT IS CAPABLE OF SOURCING UP TO 15mA AND SINKING UP TO 30mA OF OUTPUT CURRENT. 3.3V 0.1F 2.2F VDD REF_P REFIN 0.1F 10F MAX12528 0.1F REF_N 0.1F COM_ REFOUT 0.1F GND 0.1F Figure 12. External Buffered (MAX4230) Reference Drive Using a MAX6029 Bandgap Reference Buffered External Reference Drives Multiple ADCs The buffered external reference mode allows for more control over the MAX12528 reference voltage and allows multiple converters to use a common reference. The REFIN input impedance is >50M. Figure 12 shows the MAX6029 precision 2.048V bandgap reference used as a common reference for multiple converters. The 2.048V output of the MAX6029 passes through a single-pole 10Hz LP filter to the MAX4230. The MAX4250 buffers the 2.048V reference and provides additional 10Hz LP filtering before its output is applied to the REFIN input of the MAX12528. Unbuffered External Reference Drives Multiple ADCs The unbuffered external reference mode allows for precise control over the MAX12528 reference and allows multiple converters to use a common reference. Connecting REFIN to GND disables the internal reference, ______________________________________________________________________________________ 23 MAX12528 Dual, 80Msps, 12-Bit, IF/Baseband ADC 3.3V 3V 0.1F 0.1F 1 2.2F 5 MAX6029 (EUK30) 20k 1% REF_P REFOUT 0.1F 20k 1% 2 VDD 10F MAX12528 2.413V 1 4 REF_N 47 0.1F MAX4230 3 0.47F 330F 6V 10F 6V 1.47k 52.3k 1% COM_ 0.1F 4 47 MAX4230 3 3.3V 330F 6V 10F 6V 52.3k 1% 1.47k 0.1F 4 47 REF_P MAX4230 3 2.2F 0.880V 1 20k 1% REFIN GND 1.647V 1 20k 1% 0.1F 0.1F VDD REFOUT 0.1F 10F 6V 330F 6V 10F 0.1F 0.1F MAX12528 1.47k REF_N 0.1F 20k 1% COM_ 0.1F GND REFIN Figure 13. External Unbuffered Reference Driving Multiple ADCs allowing REF_P, REF_N, and COM_ to be driven directly by a set of external reference sources. Figure 13 uses a MAX6029 precision 3.000V bandgap reference as a common reference for multiple converters. A seven-component resistive divider chain follows the MAX6029 voltage reference. The 0.47F capacitor along this chain creates a 10Hz LP filter. Three MAX4230 amplifiers buffer taps along this resistor chain providing 2.413V, 1.647V, and 0.880V to the MAX12528 REF_P, REF_N, and COM_ reference inputs. The feedback around the MAX4230 op amps provides additional 10Hz LP filtering. Reference voltages 2.413V and 0.880V set the full-scale analog input 24 range for the converter to 1.022V ([VREF_P - VREF_N] x 2/3). Note that one single power supply for all active circuit components removes any concern regarding powersupply sequencing when powering up or down. Grounding, Bypassing, and Board Layout The MAX12528 requires high-speed board layout design techniques. Refer to the MAX12528 EV kit data sheet for a board layout reference. Locate all bypass capacitors as close to the device as possible, preferably on the same side as the ADC, using surface- ______________________________________________________________________________________ Dual, 80Msps, 12-Bit, IF/Baseband ADC Parameter Definitions Integral Nonlinearity (INL) INL is the deviation of the values on an actual transfer function from a straight line. For the MAX12528, this straight line is between the endpoints of the transfer function, once offset and gain errors have been nullified. INL deviations are measured at every step of the transfer function 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 MAX12528, DNL deviations are measured at every step of the transfer function and the worst-case deviation is reported in the Electrical Characteristics table. 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. Ideally, the midscale MAX12528 transition occurs at 0.5 LSB above midscale. The offset error is the amount of deviation between the measured midscale transition point and the ideal midscale transition point. 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. The slope of the actual transfer function is measured between two data points: positive full scale and negative full scale. Ideally, the positive full-scale MAX12528 transition occurs at 1.5 LSBs below positive full scale, and the negative full-scale transition occurs at 0.5 LSB above negative full scale. The gain error is the difference of the measured transition points minus the difference of the ideal transition points. Small-Signal Noise Floor (SSNF) SSNF is the integrated noise and distortion power in the Nyquist band for small-signal inputs. The DC offset is excluded from this noise calculation. For this converter, a small signal is defined as a single tone with an amplitude of -35dBFS. This parameter captures the thermal and quantization noise characteristics of the data converter and can be used to help calculate the overall noise figure of a digital receiver signal path. 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): SNR[max] = 6.02 x N + 1.76 In reality, there are other noise sources besides quantization noise: thermal noise, reference noise, clock jitter, etc. SNR is computed by taking the ratio of the RMS signal to the RMS noise. RMS noise includes all spectral components to the Nyquist frequency excluding the fundamental, the first six harmonics (HD2 through HD7), and the DC offset. SNR = 20 x log (SIGNALRMS / NOISERMS) 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. ______________________________________________________________________________________ 25 MAX12528 mount devices for minimum inductance. Bypass VDD to GND with a 220F ceramic capacitor in parallel with at least one 10F, one 4.7F, and one 0.1F ceramic capacitor. Bypass OVDD to GND with a 220F ceramic capacitor in parallel with at least one 10F, one 4.7F, and one 0.1F ceramic capacitor. High-frequency bypassing/decoupling capacitors should be located as close as possible to the converter supply pins. Multilayer boards with ample ground and power planes produce the highest level of signal integrity. All grounds and the exposed backside paddle of the MAX12528 package (package code: T6800-2) must be connected to the same ground plane. The MAX12528 relies on the exposed backside paddle connection for a low-inductance ground connection. Isolate the ground plane from any noisy digital system ground planes such as a DSP or output buffer ground. 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 parasitic components are balanced equally. Refer to the MAX12528 EV kit data sheet for an example of symmetric input layout. MAX12528 Dual, 80Msps, 12-Bit, IF/Baseband ADC 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: V22 + V32 + V4 2 + V52 + V62 + V72 THD = 20 x log V1 where V1 is the fundamental amplitude, and V2 through V7 are the amplitudes of the 2nd- through 7th-order harmonics (HD2 through HD7). 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. Intermodulation Distortion (IMD) 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 fIN1 and fIN2. The individual input tone levels are at -7dBFS. The intermodulation products are as follows: 2nd-Order Intermodulation products (IM2): fIN1 = fIN2, fIN2 - fIN1 3rd-Order Intermodulation products (IM3): 2 x fIN1 - fIN2, 2 x fIN2 - fIN1, 2 x fIN1 + fIN2, 2 x fIN2 + fIN1 4th-Order Intermodulation products (IM4): 3 x fIN1 - fIN2, 3 x fIN2 - fIN1, 3 x fIN1 + fIN2, 3 x fIN2 + fIN1, 2 x fIN1 - 2 x fIN2, 2 x fIN1 + 2 x fIN2, 2 x fIN2 - 2 x fIN1 5th-Order Intermodulation products (IM5): 3 x fIN1 - 2 x fIN2, 3 x fIN2 - 2 x fIN1, 3 x fIN1 + 2 x fIN2, 3 x fIN2 + 2 x fIN1, 4 x fIN1 - fIN2, 4 x fIN2 - fIN1, 4 x fIN1 + fIN2, 4 x fIN2 + fIN1 Note that the two-tone intermodulation distortion is measured with respect to a single-carrier amplitude and not the peak-to-average input power of both input tones. 3rd-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 fIN1 and fIN2. The individual input tone levels are at -7dBFS. The 3rdorder intermodulation products are 2 x fIN1 - fIN2, 2 x fIN2 - fIN1, 2 x fIN1 + fIN2, 2 x fIN2 + fIN1. Aperture Jitter Figure 14 shows the aperture jitter (tAJ), which is the sample-to-sample variation in the aperture delay. 26 CLKN CLKP tAD ANALOG INPUT tAJ SAMPLED DATA T/H HOLD TRACK HOLD Figure 14. T/H Aperture Timing 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 (Figure 14). Full-Power Bandwidth A large -0.2dBFS 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. Output Noise (nOUT) The output noise (nOUT) parameter is similar to thermal plus quantization noise and is an indication of the converter's overall noise performance. No fundamental input tone is used to test for nOUT. IN_P, IN_N, and COM_ are connected together and 1024k data points are collected. nOUT is computed by taking the RMS value of the collected data points after the mean is removed. Overdrive Recovery Time Overdrive recovery time is the time required for the ADC to recover from an input transient that exceeds the full-scale limits. The MAX12528 specifies overdrive recovery time using an input transient that exceeds the full-scale limits by 10%. The MAX12528 requires one clock cycle to recover from an overdrive condition. Crosstalk Coupling onto one channel being driven by a (-0.5dBFS) signal when the adjacent interfering channel is driven by a full-scale signal. Measurement includes all spurs resulting from both direct coupling and mixing components. ______________________________________________________________________________________ Dual, 80Msps, 12-Bit, IF/Baseband ADC Offset Matching Like gain matching, offset matching is a figure of merit that indicates how well the offsets between the two channels are matched to each other. The same input signal is applied to both channels and the maximum deviation in offset is reported (typically in %FSR) as offset matching. 46 45 44 43 42 41 D6B D5B D7B D8B D9B D10B D11B OVDD DAV 50 49 48 47 N.C. D0A 51 N.C. D1A D3A D2A D4A TOP VIEW DORB Pin Configuration 40 39 38 37 36 35 D5A 52 34 D4B D6A 53 33 D3B D7A 54 32 D2B D8A 55 31 D1B D9A 56 30 D0B D10A 57 29 N.C. D11A 58 28 N.C. DORA 59 27 OVDD OVDD 60 26 VDD MAX12528 VDD 61 25 VDD VDD 62 24 VDD VDD 63 23 VDD G/T 64 22 DIV4 PD 65 21 DIV2 SHREF 66 20 CLKP EXPOSED PADDLE (GND) REFOUT 67 19 CLKN REFIN 68 GND COMA INBP GND 10 11 12 13 14 15 16 17 INBN GND 9 GND INAN 8 GND GND 7 COMB 6 REFBP 5 REFBN 4 GND 3 REFAP 2 REFAN 1 INAP 18 DIFFCLK/SECLK THIN QFN ______________________________________________________________________________________ 27 MAX12528 Gain Matching Gain matching is a figure of merit that indicates how well the gains between the two channels are matched to each other. The same input signal is applied to both channels and the maximum deviation in gain is reported (typically in dB) as gain matching. Package Information (The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information, go to www.maxim-ic.com/packages.) 68L QFN THIN.EPS MAX12528 Dual, 80Msps, 12-Bit, IF/Baseband ADC PACKAGE OUTLINE 68L THIN QFN, 10x10x0.8mm 21-0142 C 1 2 PACKAGE OUTLINE 68L THIN QFN, 10x10x0.8mm 21-0142 C 2 2 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. 28 ____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 (c) 2005 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products, Inc.