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19-3545; Rev 0; 2/05
KIT ATION EVALU ABLE AVAIL
16-Bit, 500Msps Interpolating and Modulating Dual DAC with CMOS Inputs
General Description
The MAX5895 programmable interpolating, modulating, 500Msps, dual digital-to-analog converter (DAC) offers superior dynamic performance and is optimized for high-performance, wideband single- and multicarrier transmit applications. The device integrates a selectable 2x/4x/8x interpolating filter, a digital quadrature modulator, and dual 16-bit high-speed DACs on a single IC. At 30MHz output frequency and 500Msps update rate, the in-band SFDR is 88dBc while consuming 1.1W. The device also delivers 71dB ACLR for four-carrier WCDMA at a 61.44MHz output frequency. The selectable interpolating filters allow lower input data rates while taking advantage of the high DAC update rates. These linear-phase interpolation filters ease reconstruction filter requirements and enhance the passband dynamic performance. Individual offset and gain programmability allow the user to calibrate out local oscillator (LO) feedthrough and sideband suppression errors generated by analog quadrature modulators. The MAX5895 features a fIM / 4 digital image-reject modulator. This modulator generates a quadrature-modulated IF signal that can be presented to an analog I/Q modulator to complete the upconversion process. A second digital modulation mode allows the signal to be frequency-translated with image pairs at fIM / 2 or fIM / 4. The MAX5895 features a standard 1.8V CMOS, 3.3V tolerant data input bus for easy interface. A 3.3V SPITM port is provided for mode configuration. The programmable modes include the selection of 2x/4x/8x interpolating filters, fIM / 2, fIM / 4 or no digital quadrature modulation with image rejection, channel gain and offset adjustment, and offset binary or two's complement data interface. Pin-compatible 12- and 14-bit devices are also available. Refer to the MAX5894** data sheet for the 14-bit version and the MAX5893 data sheet for the 12-bit version.
Features
71dB ACLR at fOUT = 61.44MHz (Four-Carrier WCDMA) Meets Multicarrier UMTS, cdma2000(R), GSM Spectral Masks (fOUT = 122MHz) Noise Spectral Density = -158dBFS/Hz at fOUT = 16MHz 92dBc SFDR at Low-IF Frequency (10MHz) 90dBc SFDR at High-IF Frequency (50MHz) Low Power: 511mW (fCLK = 100MHz) User Programmable Selectable 2x, 4x, or 8x Interpolating Filters <0.01dB Passband Ripple >99dB Stopband Rejection Selectable Real or Complex Modulator Operation Selectable Modulator LO Frequency: OFF, fIM / 2, or fIM / 4 Selectable Output Filter: Lowpass or Highpass Channel Gain and Offset Adjustment EV Kit Available (Order the MAX5895EVKIT)
MAX5895
Ordering Information
PART MAX5895EGK TEMP RANGE -40C to +85C PIN-PACKAGE 68 QFN-EP* (10mm x 10mm) PKG CODE G6800-4
*EP = Exposed paddle.
Selector Guide
PART MAX5893 MAX5894** MAX5895 RESOLUTION (BITS) 12 14 16 DAC UPDATE RATE (Msps) 500 500 500 INPUT LOGIC CMOS CMOS CMOS
Applications
Base Stations: 3G Multicarrier UMTS, CDMA, and GSM Broadband Wireless Transmitters Broadband Cable Infrastructure Instrumentation and Automatic Test Equipment (ATE) Analog Quadrature Modulation Architectures
**Future product--contact factory for availability.
Simplified Diagram
DATA PORT A DAC OUTI
1x/2x/4x INTERPOLATING FILTERS
2x INTERPOLATING FILTERS
MODULATOR
DATA SYNCH AND DEMUX
Pin Configuration appears at end of data sheet. SPI is a trademark of Motorola, Inc. cdma2000 is a registered trademark of the Telecommunications Industry Association.
DATACLK DATA PORT B
DAC
OUTQ
________________________________________________________________ Maxim Integrated Products
1
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.
16-Bit, 500Msps Interpolating and Modulating Dual DAC with CMOS Inputs MAX5895
ABSOLUTE MAXIMUM RATINGS
DVDD1.8, AVDD1.8 to GND, DACREF ..................-0.3V to +2.16V AVDD3.3, AVCLK, DVDD3.3 to GND, DACREF ........-0.3V to +3.9V DATACLK, A0-A15, B0-B13, SELIQ/B15, DATACLK/B14, CS, RESET, SCLK, SDI and SDO to GND, DACREF......-0.3V to (DVDD3.3 + 0.3V) CLKP, CLKN to GND, DACREF..............-0.3V to (AVCLK + 0.3V) REFIO, FSADJ to GND, DACREF ........-0.3V to (AVDD3.3 + 0.3V) OUTIP, OUTIN, OUTQP, OUTQN to GND, DACREF..................-1V to (AVDD3.3 + 0.3V) SDO, DATACLK, DATACLK/B14 Continuous Current ..........8mA Continuous Power Dissipation (TA = +70C) 68-Pin QFN (derate 41.7mW/C above +70C) (Note 1) ...................................................................3333.3mW Junction Temperature ......................................................+150C Operating Temperature Range ...........................-40C to +85C Storage Temperature Range .............................-65C to +150C Lead Temperature (soldering, 10s) .................................+300C Thermal Resistance JC (Note 1)...................................-0.8C/W
Note 1: Thermal resistance based on a multilayer board with 4 x 4 via array in exposed paddle area.
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
(DVDD1.8 = AVDD1.8 = 1.8V, AVCLK = AVDD3.3 = DVDD3.3 = 3.3V, modulator off, 2x interpolation, DATACLK input mode, dual-port mode, 50 double-terminated outputs, external reference at 1.25V, TA = -40C to +85C, unless otherwise noted. Typical values are at TA = +25C, unless otherwise noted.) (Note 2)
PARAMETER STATIC PERFORMANCE Resolution Differential Nonlinearity Integral Nonlinearity Offset Error Offset Drift Full-Scale Gain Error Gain-Error Drift Full-Scale Output Current Output Compliance Output Resistance Output Capacitance DYNAMIC PERFORMANCE Maximum Clock Frequency Minimum Clock Frequency Maximum DAC Update Rate Minimum DAC Update Rate Maximum Input Data Rate fCLK fCLK fDAC fDAC fDATA fDATACLK = 125MHz, fOUT = 16MHz, fOFFSET = 10MHz, -12dBFS Noise Spectral Density fDATACLK = 125MHz, fOUT = 16MHz, fOFFSET = 10MHz, 0dBFS No interpolation 2x interpolation 4x interpolation 4x interpolation fDAC = fCLK or fDAC = fCLK / 2 fDAC = fCLK or fDAC = fCLK / 2 125 -157 -158 -157 -149 dBFS/ Hz 500 1 500 1 MHz MHz Msps Msps MWps ROUT COUT IOUTFS 2 -0.5 1 5 GEFS -4 DNL INL OS -0.01 16 1 3 0.003 0.03 0.6 110 20 +1.1 +4 +0.01 Bits LSB LSB %FS ppm/C %FS ppm/C mA V M pF SYMBOL CONDITIONS MIN TYP MAX UNITS
2
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16-Bit, 500Msps Interpolating and Modulating Dual DAC with CMOS Inputs
ELECTRICAL CHARACTERISTICS (continued)
(DVDD1.8 = AVDD1.8 = 1.8V, AVCLK = AVDD3.3 = DVDD3.3 = 3.3V, modulator off, 2x interpolation, DATACLK input mode, dual-port mode, 50 double-terminated outputs, external reference at 1.25V, TA = -40C to +85C, unless otherwise noted. Typical values are at TA = +25C, unless otherwise noted.) (Note 2)
PARAMETER SYMBOL CONDITIONS fDATACLK = 125MHz, interpolation off, 0dBFS fOUT = 10MHz fOUT = 30MHz fOUT = 50MHz In-Band SFDR (DC to fDATA / 2) SFDR fDATACLK = 125MHz, 2x interpolation, 0dBFS fOUT = 10MHz fOUT = 30MHz fOUT = 50MHz fDATACLK = 125MHz, 4x interpolation, 0dBFS fDATACLK = 125MHz, fOUT1 = 9MHz, fOUT2 = 10MHz, -6.1dBFS fOUT = 10MHz fOUT = 30MHz fOUT = 50MHz No interpolation 2x interpolation 4x interpolation 2x interpolation, fIM / 4 complex modulation 4x interpolation, fIM / 4 complex modulation 77 MIN TYP 90 85 73 90 89 86 92 88 90 -103 -103 -103 -74 dBc MAX UNITS
MAX5895
fDATACLK = 125MHz, fOUT1 = 79MHz, fOUT2 = 80MHz, -6.1dBFS
-75 dBc
Two-Tone IMD
TTIMD
fDATACLK = 62.5MHz, fOUT1 = 9MHz, fOUT2 = 10MHz, -6.1dBFS fDATACLK = 62.5MHz, fOUT1 = 69MHz, fOUT2 = 70MHz, -6.1dBFS
8x interpolation
-100
8x interpolation, fIM / 4 complex modulation
-75
8x, highpass fDATACLK = 62.5MHz, interpolation, fOUT1 = 179MHz, fOUT2 fIM / 4 complex = 180MHz, -6.1dBFS modulation fDATACLK = 125MHz, fOUT spaced 1MHz apart from 32MHz, -12dBFS, 2x interpolation fDATACLK = 61.44MHz, fOUT = baseband ACLR for WCDMA (Note 3) fDATACLK = 122.88MHz, fOUT = 61.44MHz fDATACLK = 122.88MHz, fOUT = 122.88MHz 4x interpolation 8x interpolation 2x interpolation, fIM / 4 complex modulation 4x interpolation, fIM / 4 complex modulation
-65
Four-Tone IMD
FTIMD
-97 80 79 75
dBc
ACLR
dB 69
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3
16-Bit, 500Msps Interpolating and Modulating Dual DAC with CMOS Inputs MAX5895
ELECTRICAL CHARACTERISTICS (continued)
(DVDD1.8 = AVDD1.8 = 1.8V, AVCLK = AVDD3.3 = DVDD3.3 = 3.3V, modulator off, 2x interpolation, DATACLK input mode, dual-port mode, 50 double-terminated outputs, external reference at 1.25V, TA = -40C to +85C, unless otherwise noted. Typical values are at TA = +25C, unless otherwise noted.) (Note 2)
PARAMETER Output Propagation Delay Output Rise Time Output Fall Time Output Settling Time Output Bandwidth Passband Width SYMBOL tPD tRISE tFALL CONDITIONS 1x interpolation (Note 4) 10% to 90% (Note 5) 10% to 90% (Note 5) To 0.5% (Note 5) -1dB bandwidth (Note 6) Ripple <-0.01dB 0.604 x fDATA, 2x interpolation Stopband Rejection 0.604 x fDATA, 4x interpolation 0.604 x fDATA, 8x interpolation 1x interpolation Data Latency 2x interpolation 4x interpolation 8x interpolation DAC INTERCHANNEL MATCHING Gain Match Gain-Match Tempco Phase Match Phase-Match Tempco DC Gain Match Channel-to-Channel Crosstalk REFERENCE Reference Input Range Reference Output Voltage Reference Input Resistance Reference Voltage Drift CMOS LOGIC INPUT/OUTPUT (A15-A0, SELIQ/B15, DATACLK/B14, B13-B0, DATACLK) Input High Voltage Input Low Voltage Input Current Input Capacitance VIH VIL IIN CIN 1 3 0.7 x DVDD1.8 0.3 x DVDD1.8 20 V V A pF VREFIO RREFIO Internal reference 0.125 1.14 1.20 10 50 1.250 1.27 V V k ppm/C Gain Gain/C Phase fOUT = DC - 80MHz, IOUTFS = 20mA IOUTFS = 20mA fOUT = 60MHz, IOUTFS = 20mA IOUTFS = 20mA fOUT = 50MHz, fDAC = 250MHz, 0dBFS -0.2 0.1 0.02 0.13 0.006 0.04 -95 +0.2 dB ppm/C Deg Deg/C dB dB MIN TYP 2.9 0.75 1.0 11 240 0.4 x fDATA 100 100 100 22 70 146 311 Clock Cycles dB MAX UNITS ns ns ns ns MHz
Phase/C fOUT = 60MHz, IOUTFS = 20mA
4
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16-Bit, 500Msps Interpolating and Modulating Dual DAC with CMOS Inputs
ELECTRICAL CHARACTERISTICS (continued)
(DVDD1.8 = AVDD1.8 = 1.8V, AVCLK = AVDD3.3 = DVDD3.3 = 3.3V, modulator off, 2x interpolation, DATACLK input mode, dual-port mode, 50 double-terminated outputs, external reference at 1.25V, TA = -40C to +85C, unless otherwise noted. Typical values are at TA = +25C, unless otherwise noted.) (Note 2)
PARAMETER Output High Voltage Output Low Voltage Output Leakage Current Rise/Fall Time CLOCK INPUT (CLKP, CLKN) Differential Input Voltage Swing Differential Input Slew Rate Common-Mode Voltage Input Resistance Input Capacitance Minimum Clock Duty Cycle Maximum Clock Duty Cycle CLKP/CLKN, DATACLK TIMING (Figure 4, Note 7) CLK to DATACLK Delay Data Hold Time, DATACLK Input/Output (Pin 14) Data Setup Time, DATACLK Input/Output (Pin 14) Data Hold Time, DATACLK/B14 Input/Output (Pin 27) Data Setup Time, DATACLK/B14 Input/Output (Pin 27) SCLK Frequency CS Setup Time Input Hold Time Input Setup Time Data Valid Duration tD tDH tDS tDH tDS DATACLK output mode, CLOAD = 10pF Capturing rising edge Capturing falling edge Capturing rising edge Capturing falling edge Capturing rising edge Capturing falling edge Capturing rising edge Capturing falling edge 1.0 2.1 0.4 -0.7 1.0 2.3 0.2 -0.4 10 2.5 0 4.5 6.5 16.5 6.2 ns ns ns ns ns VCOM RCLK CCLK AC-coupled VDIFF Sine-wave input Square-wave input >1.5 >0.5 >100 AVCLK / 2 5 3 45 55 VP-P V/s V k pF % % SYMBOL VOH VOL 200A load 200A load Three-state CLOAD = 10pF, 20% to 80% 1 1.5 CONDITIONS MIN 0.8 x DVDD3.3 0.2 x DVDD3.3 TYP MAX UNITS V V A ns
MAX5895
SERIAL-PORT INTERFACE TIMING (Figure 3, Note 7) fSCLK tSS tSDH tSDS tSDV MHz ns ns ns ns
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5
16-Bit, 500Msps Interpolating and Modulating Dual DAC with CMOS Inputs MAX5895
ELECTRICAL CHARACTERISTICS (continued)
(DVDD1.8 = AVDD1.8 = 1.8V, AVCLK = AVDD3.3 = DVDD3.3 = 3.3V, modulator off, 2x interpolation, DATACLK input mode, dual-port mode, 50 double-terminated outputs, external reference at 1.25V, TA = -40C to +85C, unless otherwise noted. Typical values are at TA = +25C, unless otherwise noted.) (Note 2)
PARAMETER POWER SUPPLIES Digital Supply Voltage Digital I/O Supply Voltage Clock Supply Voltage Analog Supply Voltage DVDD1.8 DVDD3.3 AVCLK AVDD3.3 AVDD1.8 IAVDD3.3 Analog Supply Current IAVDD1.8 Digital Supply Current Digital I/O Supply Current Clock Supply Current Total Power Dissipation IDVDD1.8 IDVDD3.3 IAVCLK PTOTAL AVDD3.3 Power-Down Current All I/O are static high or low, bit 2 to bit 4 of address 00h are set high AVDD1.8 DVDD1.8 DVDD3.3 AVCLK AVDD3.3 Power-Supply Rejection Ratio PSRRA (Note 8) fCLK = 100MHz, 2x interpolation, 0dBFS, fOUT = 10MHz, DATACLK output mode fCLK = 100MHz, 2x interpolation, 0dBFS, fOUT = 10MHz, DATACLK output mode fCLK = 100MHz, 2x interpolation, 0dBFS, fOUT = 10MHz, DATACLK output mode fCLK = 100MHz, 2x interpolation, 0dBFS, fOUT = 10MHz, DATACLK output mode fCLK = 100MHz, 2x interpolation, 0dBFS, fOUT = 10MHz, DATACLK output mode 1.71 3.0 3.135 3.135 1.71 1.8 3.3 3.3 3.3 1.8 110 10 54 7 3 511 450 1 10 100 1 0.125 %FS/V A 1.89 3.6 3.465 3.465 1.89 130 mA 15 65 10 5 mA mA mA mW V V V V SYMBOL CONDITIONS MIN TYP MAX UNITS
Note 2: All specifications are 100% tested at TA +25C. Specifications at TA < +25C are guaranteed by design and characterization data. Note 3: 3.84MHz bandwidth, single carrier. Note 4: Excludes data latency. Note 5: Measured single-ended into a 50 load. Note 6: Excludes sin(x)/x rolloff. Note 7: Guaranteed by design and characterization. Note 8: Parameter defined as the change in midscale output caused by a 5% variation in the nominal supply voltage.
6
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16-Bit, 500Msps Interpolating and Modulating Dual DAC with CMOS Inputs MAX5895
Typical Operating Characteristics
(DVDD1.8 = AVDD1.8 = 1.8V, AVCLK = AVDD3.3 = DVDD3.3 = 3.3V, modulator off, 2x interpolation, output is transformer-coupled to 50 load, TA = +25C, unless otherwise noted.)
SFDR vs. OUTPUT FREQUENCY fDATA = 125MWps, NO INTERPOLATION
MAX5895 toc01
IN-BAND SFDR vs. OUTPUT FREQUENCY fDATA = 125MWps, 2x INTERPOLATION
MAX5895 toc02
0UT-OF-BAND SFDR vs. OUTPUT FREQUENCY fDATA = 125MWps, 2x INTERPOLATION
90 80 70 SFDR (dBc) 60 50 40 30 20 -6dBFS -12dBFS
MAX5895 toc03
120 -0.1dBFS 100 80 SFDR (dBc) 60 40 20 0 0 10 20 30 40 50 -6dBFS
120 100 80 SFDR (dBc) -6dBFS -0.1dBFS
100 -0.1dBFS
-12dBFS
-0.1dBFS
60 40 20 0
-12dBFS
SPURS MEASURED BETWEEN 0MHz AND 62.5MHz 0 10 20 30 40 50
10 0 0
SPURS MEASURED BETWEEN 62.5MHz AND 125MHz 10 20 30 40 50
60
OUTPUT FREQUENCY (MHz)
OUTPUT FREQUENCY (MHz)
OUTPUT FREQUENCY (MHz)
IN-BAND SFDR vs. OUTPUT FREQUENCY fDATA = 125MWps, 2x INTERPOLATION
MAX5895 toc04
IN-BAND SFDR vs. OUTPUT FREQUENCY fDATA = 125MWps, 4x INTERPOLATION
MAX5895 toc05
OUT-OF-BAND SFDR vs. OUTPUT FREQUENCY fDATA = 125MWps, 4x INTERPOLATION
-6dBFS 80 70 60 SFDR (dBc) 50 40 30 20 -12dBFS -0.1dBFS
MAX5895 toc06
90 80 70 60 SFDR (dBc) 50 40 30 20 10 0
-6dBFS
120 100 80 SFDR (dBc) -6dBFS -0.1dBFS
90
-0.1dBFS
-12dBFS
60 40
-12dBFS
UPPER SIDEBAND MODULATION SPURS MEASURED BETWEEN 62.5MHz AND 125MHz 62.5 72.5 82.5 92.5 102.5 112.5
20 0 0 SPURS MEASURED BETWEEN 0MHz AND 62.5MHz 10 20 30 40 50 10 0 0
SPURS MEASURED BETWEEN 62.5MHz AND 250MHz 10 20 30 40 50
OUTPUT FREQUENCY (MHz)
OUTPUT FREQUENCY (MHz)
OUTPUT FREQUENCY (MHz)
IN-BAND SFDR vs. OUTPUT FREQUENCY fDATA = 125MWps, 4x INTERPOLATION
MAX5895 toc07
IN-BAND SFDR vs. OUTPUT FREQUENCY fDATA = 125MWps, 4x INTERPOLATION
MAX5895 toc08
90 80 70
-0.1dBFS
80 70 60 SFDR (dBc)
-6dBFS
-0.1dBFS
-12dBFS 100 TWO-TONE IMD (-dBc) 80 60 40 20 1MHz CARRIER SPACING 0 0 10 20 30 40
SFDR (dBc)
60 50 40 30 20 10 0 75
-6dBFS -12dBFS
50 40 30 20
-9dBFS -6dBFS
-12dBFS
LOWER SIDEBAND MODULATION SPURS MEASURED BETWEEN 62.5MHz AND 125MHz 85 95 105 115 125
10 0 125
UPPER SIDEBAND MODULATION SPURS MEASURED BETWEEN 62.5MHz AND 187.5MHz 135 145 155 165 175
50
OUTPUT FREQUENCY (MHz)
OUTPUT FREQUENCY (MHz)
CENTER FREQUENCY (MHz)
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MAX5895 toc09
100
90
TWO-TONE IMD vs. OUTPUT FREQUENCY fDATA = 125MWps, NO INTERPOLATION
120
7
16-Bit, 500Msps Interpolating and Modulating Dual DAC with CMOS Inputs MAX5895
Typical Operating Characteristics (continued)
(DVDD1.8 = AVDD1.8 = 1.8V, AVCLK = AVDD3.3 = DVDD3.3 = 3.3V, modulator off, 2x interpolation, output is transformer-coupled to 50 load, TA = +25C, unless otherwise noted.)
TWO-TONE IMD vs. OUTPUT FREQUENCY fDATA = 125MWps, 2x INTERPOLATION
MAX5895 toc10
TWO-TONE IMD vs. OUTPUT FREQUENCY fDATA = 125MWps, 4x INTERPOLATION
MAX5895 toc11
GAIN MISMATCH vs. TEMPERATURE fDATA = 125MWps, 2x INTERPOLATION
fOUT = 22.7MHz AOUT = -6dBFS GAIN MISMATCH (dB) 0.075
MAX5895 toc12
120 100 TWO-TONE IMD (-dBc) 80 60 40 20 0 0 1MHz CARRIER SPACING COMPLEX MODULATION FOR OUTPUT FREQUENCIES GREATER THAN 50MHz 25 50 75 100 -9dBFS -6dBFS -12dBFS
120
-6dBFS -12dBFS
0.100
TWO-TONE IMD (-dBc)
90
60 -9dBFS 30 1MHz CARRIER SPACING COMPLEX MODULATION FOR OUTPUT FREQUENCIES GREATER THAN 50MHz 0 30 60 90 120 150
0.050
0.025
0
0 -40 -15 10 35 60 85 CENTER FREQUENCY (MHz) TEMPERATURE (C)
CENTER FREQUENCY (MHz)
MULTITONE POWER RATIO PLOT fDATA = 125MWps, 2x INTERPOLATION
-20 OUTPUT POWER (dBm) -30 -40 DNL (LSB) -50 -60 -70 -80 -90 -100 -110 fCENTER = 35.7MHz, 1MHz TONE SPACING -1 AOUT1 THROUGH AOUT8 = -18dBFS, SPAN = 25MHz
MAX5895 toc13
DIFFERENTIAL NONLINEARITY vs. DIGITAL INPUT CODE
MAX5895 toc14
INTEGRAL NONLINEARITY vs. DIGITAL INPUT CODE
4 3 2 INL (LSB) 1 0 -1 -2 -3 -4 -5
MAX5895 toc15
-10
5 4 3 2 1 0
5
8192 0
24586 40960 57344 65536 16384 32768 49152 DIGITAL INPUT CODE
8192 0 16384
24576 32768
40960
57344 65536
49152 DIGITAL INPUT CODE
SUPPLY CURRENTS vs. DAC UPDATE RATE 2x INTERPOLATION, fOUT = 5MHz
MAX5895 toc16
SUPPLY CURRENTS vs. DAC UPDATE RATE 4x INTERPOLATION, fOUT = 5MHz
MAX5895 toc17
SUPPLY CURRENTS vs. DAC UPDATE RATE 8x INTERPOLATION, fOUT = 5MHz
450 400 SUPPLY CURRENT (mA) 350 300 250 200 150 100 50 0 3.3V TOTAL 1.8V TOTAL
MAX5895 toc18
500 450 400 SUPPLY CURRENT (mA) 350 300 250 200 150 100 50 0 100 150 200 fDAC (MHz) 250 3.3V TOTAL 1.8V TOTAL
500 450 400 SUPPLY CURRENT (mA) 350 300 250 200 150 100 50 0 3.3V TOTAL 1.8V TOTAL
500
300
100
200
300 fDAC (MHz)
400
500
100
200
300 fDAC (MHz)
400
500
8
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16-Bit, 500Msps Interpolating and Modulating Dual DAC with CMOS Inputs MAX5895
Typical Operating Characteristics (continued)
(DVDD1.8 = AVDD1.8 = 1.8V, AVCLK = AVDD3.3 = DVDD3.3 = 3.3V, modulator off, 2x interpolation, output is transformer-coupled to 50 load, TA = +25C, unless otherwise noted.)
NOISE DENSITY vs. DAC UPDATE RATE fOUT = 16MHz, 10MHz OFFSET
MAX5895 toc19
WCDMA ACLR vs. OUTPUT FREQUENCY fDATA = 122.88MWps, 4x INTERPOLATION
MAX5895 toc20
WCDMA ACLR vs. OUTPUT FREQUENCY fDATA = 76.8MWps, 4x INTERPOLATION
SINGLE-CARRIER ALTERNATE CHANNEL SINGLE-CARRIER ADJACENT CHANNEL
MAX5895 toc21
-100 -110 NOISE DENSITY (dBFS/Hz) -120 2x, 4x, AND 8x INTERPOLATION AOUT = -12dBFS
100 90 80 ACLR (dB) 70 60 50 40 FOUR-CARRIER ALTERNATE CHANNEL FOUR-CARRIER ADJACENT CHANNEL SINGLE-CARRIER ALTERNATE CHANNEL SINGLE-CARRIER ADJACENT CHANNEL
100 90 80 ACLR (dB) 70 60 50 40 FOUR-CARRIER ALTERNATE CHANNEL FOUR-CARRIER ADJACENT CHANNEL
-130 -140 -150 -160 -170 -180 100 200 300 fDAC (MHz) 400 500
0
40
80 fCENTER (MHz)
120
160
0
40 fCENTER (MHz)
80
WCDMA ACLR SPECTRAL PLOT fDATA = 61.44MWps, 8x INTERPOLATION
MAX5895 toc22
FOUR-CARRIER WCDMA ACLR SPECTRAL PLO fDATA = 61.44MWps, 8x INTERPOLATION
-30 -40 OUTPUT POWER (dBm) -50 CARRIER = -17dBm -60 ACLR2 = 74dB ACLR1 = 73dB -70 -80 -90 -100 -110 -120
MAX5895 toc23
-20 -30 -40 OUTPUT POWER (dBm) -50 CARRIER = -11dBm -60 ACLR2 = 77dB ACLR1 = 76dB -70 -80 -90 -100 -110 -120 fCENTER = 61.44MHz, SPAN = 25.5MHz
-20
ACLR1 = 75dB
ACLR2 = 76dB
ACLR1 = 72dB
fCENTER = 61.44MHz, SPAN = 40.6MHz
WCDMA ACLR SPECTRAL PLOT fDATA = 122.88MWps, 4x INTERPOLATION
MAX5895 toc24
FOUR-CARRIER WCDMA ACLR SPECTRAL PLOT fDATA = 122.88MWps, 4x INTERPOLATION
-30 -40 OUTPUT POWER (dBm) -50 CARRIER = -20dBm -60 ACLR2 = 67dB ACLR1 = 66dB -70 -80 -90 -100 -110 -120
MAX5895 toc25
-20 -30 -40 OUTPUT POWER (dBm) -50 CARRIER = -14dBm -60 ACLR2 = 73dB ACLR1 = 71dB -70 -80 -90 -100 -110 -120 fCENTER = 122.88MHz, SPAN = 25.5MHz
-20
ACLR1 = 66dB
ACLR1 = 70dB
ACLR2 = 72dB
fCENTER = 122.88MHz, SPAN = 40.6MHz
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ACLR2 = 67dB
ACLR2 = 72dB
9
16-Bit, 500Msps Interpolating and Modulating Dual DAC with CMOS Inputs MAX5895
Pin Description
PIN 1 2 3, 4, 5 6, 21, 30, 37 NAME CLKP CLKN N.C. DVDD1.8 Noninverting Differential Clock Input Inverting Differential Clock Input Internally Connected. Do not connect. Digital Power Supply. Accepts a 1.71V to 1.89V supply range. Bypass each pin to ground with a 0.1F capacitor as close to the pin as possible. A-Port Data Inputs. Dual-port mode: I-channel data input. Data is latched on the rising/falling edge (programmable) of the DATACLK. Single-port mode: I-channel and Q-channel data input, with SELIQ. CMOS I/O Power Supply. Accepts a 3.0V to 3.6V supply range. Bypass each pin to ground with a 0.1F capacitor as close to the pin as possible. Programmable Data Clock Input/Output. See the DATACLK Modes section for details. Select I/Q-Channel Input or B-Port MSB Input. Single-port mode: If SELIQ = LOW, data is latched into Q-channel on the rising/falling edge (programmable) of the DATACLK. If SELIQ = HIGH, data is latched into I-channel on the rising/falling edge (programmable) of the DATACLK. Dual-port mode: Q-channel MSB input. FUNCTION
7-12, 15-20, 22-25
A15-A0
13, 44 14
DVDD3.3 DATACLK
26
SELIQ/B15
27
Alternate DATACLK Input/Output or B-Port Bit 14 Input. Single-port mode: See the DATACLK Modes section for details. DATACLK/B14 Dual-port mode: Q-channel bit 14 input. If unused connect to GND. B-Port Data Bits 13-0. Dual-port mode: Q-channel inputs. Data is latched on the rising/falling (programmable) edge of the DATACLK. Single-port mode: Connect to GND. Serial-Port Data Output Serial-Port Data Input Serial-Port Clock Input. Data on SDI is latched on the rising edge of SCLK. Serial-Port Interface Select. Drive CS low to enable serial-port interface. Reset Input. Set RESET low during power-up. Reference Input/Output. Bypass to ground with a 1F capacitor as close to the pin as possible. Current-Set Resistor Return Path. For a 20mA full-scale output current, connect a 2k resistor between FSADJ and DACREF. Internally connected to GND. Do not use as an external ground connection. Full-Scale Adjust Input. This input sets the full-scale output current of the DAC. For a 20mA fullscale output current, connect a 2k resistor between FSADJ and DACREF.
28, 29, 31-36, 38-43
B13-B0
45 46 47 48 49 50 51
SDO SDI SCLK CS RESET REFIO DACREF
52
FSADJ
10
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16-Bit, 500Msps Interpolating and Modulating Dual DAC with CMOS Inputs
Pin Description (continued)
PIN 53, 67 54, 56, 59, 61, 64, 66 55, 60, 65 57 58 62 63 68 EP NAME AVDD1.8 GND AVDD3.3 OUTQN OUTQP OUTIN OUTIP AVCLK GND FUNCTION Low Analog Power Supply. Accepts a 1.71V to 1.89V supply range. Bypass each pin to GND with a 0.1F capacitor as close to the pin as possible. Ground Analog Power Supply. Accepts a 3.135V to 3.465V supply range. Bypass each pin to GND with a 0.1F capacitor as close to the pin as possible. Inverting Differential DAC Current Output for Q-Channel Noninverting Differential DAC Current Output for Q-Channel Inverting Differential DAC Current Output for I-Channel Noninverting Differential DAC Current Output for I-Channel Clock Power Supply. Accepts a 3.135V to 3.465V supply range. Bypass to ground with a 0.1F capacitor as close to the pin as possible. Exposed Pad. Must be connected to GND through a low-impedance path.
MAX5895
Functional Diagram
MODULATOR
DIGITAL OFFSET ADJUST
DIGITAL GAIN ADJUST OUTIP
2x INTERPOLATING FILTER
2x INTERPOLATING FILTER
2x INTERPOLATING FILTER
MUX
MUX
IDAC OUTIN fDAC
A0-A15
DATA SYNCH AND DEMUX
DATACLK B0-B15 SELIQ
I Q fIM / 2, fIM / 4 I Q
MAX5895
DIGITAL OFFSET ADJUST
DIGITAL GAIN ADJUST OUTQP
MUX
2x INTERPOLATING FILTER
/2
CONTROL REGISTERS RESET SERIAL INTERFACE REFERENCE
2x INTERPOLATING FILTER
/2
MUX
2x INTERPOLATING FILTER
/2 CLKN
QDAC OUTQN
fDAC
/2
fCLK CLOCK BUFFERS AND DIVIDERS
SDO
SDI
CS
SCLK
DACREF
FSADJ
REFIO
CLKP
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11
16-Bit, 500Msps Interpolating and Modulating Dual DAC with CMOS Inputs MAX5895
Detailed Description
The MAX5895 dual, 500Msps, high-speed, 16-bit, current-output DAC provides superior performance in communication systems requiring low-distortion analog-signal reconstruction. The MAX5895 combines two DAC cores with 8x/4x/2x/1x programmable digital interpolation filters, a digital quadrature modulator, an SPIcompatible serial interface for programming the device, and an on-chip 1.20V reference. The full-scale output current range is programmable from 2mA to 20mA to optimize power dissipation and gain control. Each channel contains three selectable interpolating filters making the MAX5895 capable of 1x, 2x, 4x, or 8x interpolation, which allows for low-input and high-output data rates. When operating in 8x interpolation mode, the interpolator increases the DAC conversion rate by a factor of eight, providing an eight-fold increase in separation between the reconstructed waveform spectrum and its first image. The MAX5895 accepts either two's complement or offset binary input data format and can operate from either a single- or dual-port input bus. The MAX5895 includes modulation modes at fIM / 2 and fIM / 4, where fIM is the data rate at the input of the modulator. If 2x interpolation is used, this data rate is 2x the input data rate. If 4x or 8x interpolation is used, this data rate is 4x the input data rate. Table 1 summarizes the modulator operating data rates for dual-port mode. The power-down modes can be used to turn off each DAC's output current or the entire digital section. Programming both DACs into power-down simultaneously will automatically power down the digital interpolator filters. Note the SPI section is always active. The analog and digital sections of the MAX5895 have separate power-supply inputs (AV DD3.3 , AV DD1.8 , AVCLK, DVDD3.3, and DVDD1.8), which minimize noise coupling from one supply to the other. AVDD1.8 and DVDD1.8 operate from a typical 1.8V supply, and all other supply inputs operate from a typical 3.3V supply.
Serial Interface
The SPI-compatible serial interface programs the MAX5895 registers. The serial interface consists of the CS, SDI, SCLK, and SDO. Data is shifted into SDI on the rising edge of the SCLK when CS is low. When CS is high, data presented at SDI is ignored and SDO is in high-impedance mode. Note: CS must transition high after each read/write operation. SDO is the serial data output for reading registers to facilitate easy debugging during development. SDI and SDO can be connected together to form a 3-wire serial interface bus or remain separate and form a 4-wire SPI bus. The serial interface supports two-byte transfer in a communication cycle. The first byte is a control byte written to the MAX5895 only. The second byte is a data byte and can be written to or read from the MAX5895.
Table 1. Quadrature Modulator Operating Data Rates (fIM is the Data Rate at the Input of the Modulator) for Dual-Port Mode
INTERPOLATION RATE 1x 2x 4x 8x MODULATION MODE (fLO) fIM / 2 fIM / 4 fIM / 2 fIM / 4 fIM / 2 fIM / 4 fIM / 2 fIM / 4 MODULATION FREQUENCY RELATIVE TO fDAC fDAC / 2 fDAC / 4 fDAC / 2 fDAC / 4 fDAC / 2 fDAC / 4 fDAC / 4 fDAC / 8 MODULATION FREQUENCY RELATIVE TO fDATA fDATA / 2 fDATA / 4 fDATA fDATA / 2 2 x fDATA fDATA 2 x fDATA fDATA
12
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16-Bit, 500Msps Interpolating and Modulating Dual DAC with CMOS Inputs
When writing to the MAX5895, data is shifted into SDI; data is shifted out of SDO in a read operation. Bits 0 to 3 of the control byte are the address bits. These bits set the address of the register to be written to or read from. Bits 4 to 6 of the control byte must always be set to 0. Bit 7 is a read/write bit: 0 for write operation and 1 for read operation. The most significant bit (MSB) is shifted in first in default mode. If the serial port is set to LSBfirst mode, both the control byte and data byte are shifted LSB in first. Figures 1 and 2 show the SPI serial interface operation in the default write and read mode, respectively. Figure 3 is a timing diagram for the SPI serial interface.
MAX5895
CS
SCLK
SDI
0
0
0
0
A3
A2
A1
A0
D7
D6
D5
D4
D3
D2
D1
D0
SDO
HIGH IMPEDANCE
Figure 1. SPI Serial Interface Write Cycle, MSB-First Mode
CS
READ CYCLE N - 1
READ CYCLE N
READ CYCLE N + 1
SCLK ADDRESS 10003210 HIGH IMPEDANCE DATA IGNORED ADDRESS 10003210 HIGH IMPEDANCE DATA IGNORED ADDRESS 10003210 HIGH IMPEDANCE DATA IGNORED
SDI
SDO
DATA N - 2
DATA N - 1
DATA N
Figure 2. SPI Serial Interface Read Cycle, MSB-First Mode
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13
16-Bit, 500Msps Interpolating and Modulating Dual DAC with CMOS Inputs MAX5895
tSS
CS
SCLK tSDS tSDH
SDI
tSDV
SDO
Figure 3. SPI Serial-Interface Timing Diagram
14
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16-Bit, 500Msps Interpolating and Modulating Dual DAC with CMOS Inputs
Programming Registers
Programming its registers with the SPI serial interface sets the MAX5895 operation modes. Table 2 shows all of the registers. The following are descriptions of each register.
MAX5895
Table 2. MAX5895 Programmable Registers
ADD BIT 7 BIT 6 0 = MSB first 1 = LSB first BIT 5 Software Reset 0 = Normal 1 = Reset all registers Third Interpolation Filter Configuration 0 = Lowpass 1 = Highpass BIT 4 Interpolator Power-Down 0 = Normal 1 = Power-down BIT 3 IDAC PowerDown 0 = Normal 1 = Power-down BIT 2 QDAC PowerDown 0 = Normal 1 = Power-down Mixer Modulation Mode 0 = Complex 1 = Real BIT 1 BIT 0
00h
Unused
Unused
01h
Interpolation Rate (Bit 7, Bit 6) 00 = No interpolation 01 = 2x interpolation 10 = 4x interpolation 11 = 8x interpolation 0 = Two's complement input data 1 = Offset binary input data Unused 0 = Single port (A), interleaved I/Q 1 = Dual port I/Q input
Modulation Mode (Bit 4, Bit 3) 00 = Modulation off 01 = fIM / 2 10 = fIM / 4 11 = fIM / 4
Modulation Sign 0 = e-j 1 = e+j
Unused
02h
0 = Input data latched on 0 = Clock output rising clock on DATACLK edge 1 = Clock output 1 = Input data on DATA CLK/B14 latched on falling clock edge
0 = Data clock input enabled 1 = Data clock output enabled
Data Synchronizer 0 = Enabled 1 = Disabled
Unused
03h 04h 05h 06h
8-Bit IDAC Fine-Gain Adjustment (see the Gain Adjustment section). Bit 7 is MSB and bit 0 is LSB. Default: 00h Unused 4-Bit IDAC Coarse-Gain Adjustment (see the Gain Adjustment section). Bit 3 is MSB and bit 0 is LSB. Default: Fh
10-Bit IDAC Offset Adjustment (see the Offset Adjustment section). Bits 7 to 0 of the 06h register are the MSB bits. Bit 1 and bit 0 are the LSB bits in 07h register. Default: 000h IDAC IOFFSET IDAC Offset Direction Adjustment 0 = Current on Unused Bit 1 OUTIN (see 06h 1 = Current on register) OUTIP 8-Bit QDAC Fine-Gain Adjustment (see the Gain Adjustment section). Bit 7 is MSB and bit 0 is LSB. Default: 00h Unused IDAC Offset Adjustment Bit 0 (see 06h register)
07h
08h 09h 0Ah
4-Bit QDAC Coarse-Gain Adjustment (see the Gain Adjustment section). Bit 3 is MSB and bit 0 is LSB. Default: Fh
10-Bit QDAC Offset Adjustment (see the Offset Adjustment section). Bits 7 to 0 of the 0Ah register are the MSB bits. Bit 1 and bit 0 are the LSB bits in 0Bh register. Default: 000h QDAC IOFFSET Direction 0 = Current on OUTQN 1 = Current on OUTQP QDAC Offset Adjustment Bit 1 (see 0Ah register) QDAC Offset Adjustment Bit 0 (see 0Ah register)
0Bh
Unused
0Ch 0Dh 0Eh
Reserved, do not write to these bits. Reserved, do not write to these bits. Reserved, do not write to these bits.
Conditions in bold are default states after reset.
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15
16-Bit, 500Msps Interpolating and Modulating Dual DAC with CMOS Inputs MAX5895
Address 00h Bit 6 Logic 0 (default) causes the serial port to use MSB first address/data format. When set to a logic 1, the serial port will use LSB first address/data format. Bit 5 Bit 4 When set to a logic 1, all registers reset to their default state (this bit included). Logic 1 stops the clock to the digital interpolators. DAC outputs hold last value prior to interpolator power-down. IDAC power-down mode. A logic 1 to this bit powers down the IDAC. to be e+jw, cancelling the lower image when used with an external quadrature modulator. Address 02h Bit 7 Logic 0 (default) configures the data port for two's complement. A logic 1 configures the data ports for offset binary. Bit 6 Logic 0 (default) configures the data bus for single-port, interleaved I/Q data. I and Q data enter through one 16-bit bus. Logic 1 configures the data bus for dual-port I/Q data. I and Q data enter on separate buses. Bit 5 Logic 0 (default) configures the data clock for pin 14. A logic 1 configures the data clock for pin 27 (DATACLK/B14). Bit 4 Logic 0 (default) sets the internal latches to latch the data on the rising edge of DATACLK. A logic 1 sets the internal latches to latch the data on the falling edge of DATACLK. Logic 0 (default) configures the DATACLK pin (pin 14 or pin 27) to be an input. A logic 1 configures the DATACLK pin to be an output. Logic 0 (default) enables the data synchronizer circuitry. A logic 1 disables the data synchronizer circuitry.
Bit 3 Bit 2
QDAC power-down mode. A logic 1 to this bit powers down the QDAC. Note: If both bit 2 and bit 3 are 1, the MAX5895 is in full-power-down mode, leaving only the serial interface active. Address 01h Bits 7, 6 Configure the interpolation filters according to the following table: 00 1x (no interpolation) 01 10 11 Bit 5 2x 4x 8x (default)
Bit 3
Bit 2
Logic 0 configures FIR3 as a lowpass digital filter (default). A logic 1 configures FIR3 as a highpass digital filter.
Address 03h Bits 7-0 Unused. Address 04h Bits 7-0 These 8 bits define the binary number for fine-gain adjustment of the IDAC full-scale current (see the Gain Adjustment section). Bit 7 is the MSB. Default is all zeros. Address 05h Bits 3-0 These four bits define the binary number for the coarse-gain adjustment of the IDAC fullscale current (see the Gain Adjustment section). Bit 3 is the MSB. Default is all ones. Address 06h, Bits 7 to 0; Address 07h, Bit 1 and Bit 0 These 10 bits represent a binary number that defines the magnitude of the offset added to the IDAC output (see the Offset Adjustment section). Default is all zeros.
Bits 4, 3 Configure the modulation frequency according to the following table: 00 No modulation 01 fIM / 2 modulation 10 fIM / 4 modulation (default) 11 fIM / 4 modulation where fIM is the data rate at the input of the modulator. Configures the modulation mode for either real or complex (image reject) modulation. Logic 1 sets the modulator to the real mode (default). Complex modulation is only available for fIM / 4 modulation. Quadrature modulator sign inversion. With Ichannel data leading Q-channel data by 90, logic 0 sets the complex modulation to be e -jw (default), cancelling the upper image when used with an external quadrature modulator. A logic 1 sets the complex modulation
Bit 2
Bit 1
16
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16-Bit, 500Msps Interpolating and Modulating Dual DAC with CMOS Inputs
Address 07h Bit 7 Logic 0 (default) adds the 10 bits offset current to OUTIN. A logic 1 adds the 10 bits offset current to OUTIP. Address 08h Bits 7-0 These 8 bits define the binary number for fine-gain adjustment of the QDAC full-scale current (see the Gain Adjustment section). Bit 7 is the MSB. Default is all zeros. Address 09h Bits 3-0 These four bits define the binary number for the coarse-gain adjustment of the QDAC fullscale current (see the Gain Adjustment section). Bit 3 is the MSB. Default is all ones. Address 0Ah, Bits 7 to 0; Address 0Bh, Bit 1 and Bit 0 These 10 bits represent a binary number that defines the magnitude of the offset added to the QDAC output (see the Offset Adjustment section). Default is all zeros. Address 0Bh Bit 7 Logic 0 (default) adds the 10 bits offset to OUTQN. A logic 1 adds the 10 bits offset to OUTQP. Offset Adjustment Offset adjustment is achieved by adding a digital code to the DAC inputs. The code OFFSET (see equation below), as stored in the relevant control registers, has a range from 0 to 1023 and a sign bit. The applied DAC offset is 4 times the code stored in the register, providing an offset adjustment range of 4092 LSB codes. The resolution is 4 LSB. IOFFSET = 4 x OFFSET 2
16
tively. FINE is the register content of register 04h and 08h for the I- and Q-channel, respectively. The range of coarse is from 0 to 15, with 15 being the default. The range for FINE is from 0 to 255 with 0 being the default. Given this, the gain can be adjusted in steps of approximately 0.01dB.
MAX5895
Single-Port/Dual-Port Data Input Modes
The MAX5895 is capable of capturing data in singleport and dual-port modes (selected through bit 6, address 02h). In single-port mode, the data for both channels is input through the A port (A15-A0). The channel for the input data is determined through the state of the SELIQ/B15 (pin 26) bit. When SELIQ is set to logic-high, the input data is presented to the I-channel, when set to logic-low, the input data is presented to the Q-channel. The unused B-port inputs (DATACLK/B14, B13-B0) should be grounded when running in single-port mode. Dual-port mode, as the name implies, requires that each channel receives its data from a separate data bus. SELIQ/B15 and DATACLK/B14 revert to data bit inputs for the Q-channel in dual-port mode. The MAX5895 control registers can be programmed to allow either signed or unsigned binary format (bit 7, address 02h) data in either single-port or dual-port mode. Table 3 shows the corresponding DAC output levels when using signed or unsigned data modes.
Table 3. DAC Output Code Table
DIGITAL INPUT CODE OFFSET BINARY (UNSIGNED) TWO'S COMPLEMENT (SIGNED) OUT_P OUT_N
x IOUTFS
0000 0000 0000 0000 1000 0000 0000 0000 0111 1111 1111 1111 0000 0000 0000 0000 1111 1111 1111 1111 0111 1111 1111 1111
0
IOUTFS
IOUTFS IOUTFS /2 /2 IOUTFS 0
Gain Trim Gain trimming is done by varying the full-scale current according to the following formula:
Data Synchronization Modes
Data synchronization circuitry is provided to allow operation with an input data clock. The data clock must be frequency locked to the DAC clock (f DAC), but can have arbitrary phase with respect to the DAC clock. The synchronization circuitry allows for phase jitter on the input data clock of up to 1 data clock cycles. Synchronization is initially established when the reset pin is asynchronously deasserted and the input data clock has been running for at least 4 clock cycles. Subsequently, the MAX5895 monitors the phase rela17
3 x IREF COARSE + 1 3 x IREF FINE IOUTFS = - 32 256 4 16
1024 24
where IREF is the reference current (see the Internal Reference section). COARSE is the register content of registers 05h and 09h for the I- and Q-channel, respec-
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16-Bit, 500Msps Interpolating and Modulating Dual DAC with CMOS Inputs MAX5895
tionship and detects if the phase drifts more than 1 data clock cycle. If this occurs, the synchronizer automatically reestablishes synchronization. However, during the resynchronization phase, up to 8 data words may be lost or repeated. Bit 2 of register 02h disables or enables (default) the automatic data clock phase detection. Disabling the data synchronization circuitry requires the data clock and the DAC clock phase to be locked.
Table 4. Clock Frequency Ratios in Various Modes
INPUT MODE INTERPOLATION RATE 1x Single Port 2x 4x 8x 1x Dual Port 2x 4x 8x fDATA:fCLK 1:1 1:1 1:2 1:4 1:1 1:2 1:4 1:8 fDAC:fCLK 1:2 1:1 1:1 1:1 1:1 1:1 1:1 1:1
DATACLK Modes
The MAX5895 has a main DATACLK available at pin 14. An alternate DATACLK is available at pin 27 (DATACLK/B14) when configured in single-port data input mode (bit 5, address 02h). The DATACLK can be configured to accept an input clock signal for latching the input data, or to source a clock signal that can drive up to 10pF load while latching the input data (bit 3, address 02h). If DATACLK is configured as an output, it
is frequency divided from the CLKP/CLKN input, depending on the operating mode, see Table 4.
CLKP-CLKN tCLK
DATACLK tD tDS tDH
A0-A15/B0-B15
Figure 4. Data Input Timing Diagram
18
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16-Bit, 500Msps Interpolating and Modulating Dual DAC with CMOS Inputs
The MAX5895 can be configured to latch the input data on either the rising edge or falling edge of the DATACLK signal (bit 4, address 02h). Figure 4 shows the timing requirements between the DATACLK signal and the input data bus with latching on the rising edge.
Interpolating Filter
The MAX5895 features three cascaded FIR half-band filters. The interpolating filters are enabled or disabled in combinations to support 1x (no interpolation), 2x, 4x, or 8x interpolation. Bits 7 and 6 of register 01h set the interpolation rate (see Table 2). The last interpolation fil-
MAX5895
0 -20 GAIN (dBFS) GAIN (dBFS) -40 -60 -80 -100 -120 0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 fOUT - NORMALIZED TO INPUT DATA RATE
PASSBAND DETAIL 0 -0.0002 -0.0004
0 -20 -40 -60 -80 -100 -120 0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 fOUT - NORMALIZED TO INPUT DATA RATE
PASSBAND DETAIL 0 -0.0002 -0.0004
0
0.1
0.2
0.3
0.4
0
0.1
0.2
0.3
0.4
Figure 5. Interpolation Filter Frequency Response, 2x Interpolation Mode
Figure 6. Interpolation Filter Frequency Response, 4x Interpolation Mode
0
0 -20 GAIN (dBFS) GAIN (dBFS) -40 -60 -80 -100 -120 0 1 2 3 4 5 6 7 8 fOUT - NORMALIZED TO INPUT DATA RATE
PASSBAND DETAIL 0 -0.0002 -0.0004
0 -20 -40 -60
-0.0004 3.6 3.8 4.0 4.2 4.4 PASSBAND DETAIL 0 -0.0002
-0.0002
-0.0004
0
0
0.1
0.2
0.3
0.4
-80 -100 -120 0 1 2 3 4 5 6 7 8 fOUT - NORMALIZED TO INPUT DATA RATE
Figure 7. Interpolation Filter Frequency Response, 8x Interpolation Mode (FIR3 Lowpass Mode)
Figure 8. Interpolation Filter Frequency Response, 8x Interpolation Mode (FIR3 Highpass Mode) 19
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16-Bit, 500Msps Interpolating and Modulating Dual DAC with CMOS Inputs MAX5895
ter is located after the modulator. In the 8x interpolation mode, the last filter (FIR3) can be configured as lowpass or highpass (bit 5, address 01h) to select the lower or upper sideband from the modulation output. The frequency responses of these three filters are plotted in Figures 5-8. The programmable interpolation filters multiply the MAX5895 input data rate by a factor of 2x, 4x, or 8x to separate the reconstructed waveform spectrum and the
FILTER RESPONSE
DAC image. The original spectral images, appearing at around multiples of the input data rate, are attenuated by the internal digital filters. This feature provides three benefits: 1) Image separation reduces complexity of analog reconstruction filters. 2) Lower input data rates eliminate board-level highspeed data transmission.
INPUT SPECTRUM AND FIRST FILTER RESPONSE
SIGNAL
IMAGE
NO INTERPOLATION
fS
2fS
3fS
4fS
5fS
6fS
7fS
8fS
OUTPUT SPECTRUM OF THE FIRST FILTER
SIGNAL
IMAGE
2x INTERPOLATION
fS
2fS
3fS
4fS
5fS FILTER RESPONSE
6fS
7fS
8fS
INPUT SPECTRUM AND SECOND FILTER RESPONSE
SIGNAL
IMAGE
fS
2fS
3fS
4fS
5fS
6fS
7fS
8fS
OUTPUT SPECTRUM OF THE SECOND FILTER
SIGNAL IMAGE
4x INTERPOLATION
fS
2fS
3fS
4fS
5fS
6fS
7fS
8fS
INPUT SPECTRUM AND THIRD FILTER RESPONSE
SIGNAL FILTER RESPONSE
IMAGE
fS
2fS
3fS
4fS
5fS
6fS
7fS
8fS
OUTPUT SPECTRUM OF THE THIRD FILTER
SIGNAL
IMAGE
8x INTERPOLATION
fS
2fS
3fS
4fS
5fS
6fS
7fS
8fS
Figure 9. Spectral Representation of Interpolating Filter Responses (Output Frequencies are Relative to the Data Input Frequency, fS) 20 ______________________________________________________________________________________
16-Bit, 500Msps Interpolating and Modulating Dual DAC with CMOS Inputs
3) Sin(x)/x rolloff is reduced over the effective bandwidth. Figure 9 illustrates a practical example of the benefits when using the MAX5895 in 2x, 4x, and 8x interpolation modes with the third filter configured as a lowpass filter. With no interpolation filter, the first image signal appears in the second Nyquist zone between fS / 2 and fS. The first interpolating filter removes this image. In fact, all of the images at odd numbers of fS are filtered. At the output of the first filter, the images are at 2fS, 4fS, etc. This signal is then passed to the second interpolating filter, which is
MAX5895
INPUT SPECTRUM AND FIRST FILTER RESPONSE
SIGNAL
IMAGE
FILTER RESPONSE
NO INTERPOLATION
fS
2fS
3fS
4fS
OUTPUT SPECTRUM OF THE FIRST FILTER
SIGNAL
IMAGE
2x INTERPOLATION
fS
2fS
3fS
4fS
INPUT SPECTRUM AND SECOND FILTER RESPONSE
SIGNAL
FILTER RESPONSE
IMAGE
fS
2fS
3fS
4fS
OUTPUT SPECTRUM OF THE SECOND FILTER
SIGNAL
IMAGE
4x INTERPOLATION
fS
2fS
3fS
4fS
OUTPUT SPECTRUM OF THE MODULATOR
LOWER SIDEBAND
SIGNAL
UPPER SIDEBAND
IMAGE
fS
2fS
3fS
4fS
FOR COMPLEX MODULATION THE MODULATION SIGN (BIT 1, ADDRESS 01h) SELECTS UPPER OR LOWER SIDEBAND
Figure 10. Spectral Representation of 4x Interpolation Filter with fIM / 4 Modulation (Output Frequencies are Relative to the Data Input Frequency, fS)
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21
16-Bit, 500Msps Interpolating and Modulating Dual DAC with CMOS Inputs MAX5895
SIGNAL FILTER RESPONSE NO INTERPOLATION
INPUT SPECTRUM AND FIRST FILTER RESPONSE
IMAGE
fS
2fS
3fS
4fS
5fS
6fS
7fS
8fS
OUTPUT SPECTRUM OF THE FIRST FILTER
SIGNAL
IMAGE
2x INTERPOLATION
fS
2fS
3fS
4fS FILTER RESPONSE
5fS
6fS
7fS
8fS
INPUT SPECTRUM AND SECOND FILTER RESPONSE
SIGNAL
IMAGE
fS
2fS
3fS
4fS
5fS
6fS
7fS
8fS
OUTPUT SPECTRUM OF THE SECOND FILTER
SIGNAL IMAGE
4x INTERPOLATION
fS SIGNAL UPPER SIDEBAND
2fS
3fS
4fS
5fS
6fS
7fS
8fS
OUTPUT SPECTRUM OF THE MODULATOR
LOWER SIDEBAND
IMAGE
fS 2fS 3fS 4fS 5fS 6fS FOR COMPLEX MODULATION THE MODULATION SIGN (BIT 1, ADDRESS 01h) SELECTS UPPER OR LOWER SIDEBAND INPUT SPECTRUM AND THIRD FILTER RESPONSE fS SIGNAL FILTER RESPONSE IMAGE
7fS
8fS
2fS
3fS
4fS
5fS
6fS
7fS
8fS
OUTPUT SPECTRUM OF THE THIRD FILTER fS
SIGNAL
IMAGE
8x INTERPOLATION
2fS
3fS
4fS
5fS
6fS
7fS
8fS
Figure 11. Spectral Representation of 8x Interpolation Filter with fIM / 4 Modulation and Lowpass Mode Enabled (Output Frequencies are Relative to the Data Input Frequency, fS) 22 ______________________________________________________________________________________
16-Bit, 500Msps Interpolating and Modulating Dual DAC with CMOS Inputs MAX5895
SIGNAL FILTER RESPONSE NO INTERPOLATION
INPUT SPECTRUM AND FIRST FILTER RESPONSE
IMAGE
fS
2fS
3fS
4fS
5fS
6fS
7fS
8fS
OUTPUT SPECTRUM OF THE FIRST FILTER
SIGNAL
IMAGE
2x INTERPOLATION
fS
2fS
3fS
4fS
5fS FILTER RESPONSE
6fS
7fS
8fS
INPUT SPECTRUM AND SECOND FILTER RESPONSE
SIGNAL
IMAGE
fS
2fS
3fS
4fS
5fS
6fS
7fS
8fS
OUTPUT SPECTRUM OF THE SECOND FILTER
SIGNAL IMAGE
4x INTERPOLATION
fS SIGNAL UPPER SIDEBAND
2fS
3fS
4fS
5fS
6fS
7fS
8fS
OUTPUT SPECTRUM OF THE MODULATOR
LOWER SIDEBAND
IMAGE
fS 2fS 3fS 4fS 5fS 6fS FOR COMPLEX MODULATION THE MODULATION SIGN (BIT 1, ADDRESS 01h) SELECTS UPPER OR LOWER SIDEBAND INPUT SPECTRUM AND THIRD FILTER RESPONSE fS SIGNAL IMAGE FILTER RESPONSE
7fS
8fS
2fS
3fS
4fS
5fS
6fS
7fS
8fS
OUTPUT SPECTRUM OF THE THIRD FILTER fS 2fS 3fS
SIGNAL
IMAGE
8x INTERPOLATION
4fS
5fS
6fS
7fS
8fS
Figure 12. Spectral Representation of 8x Interpolation Filter with fIM / 4 Modulation and Highpass Mode Enabled (Output Frequencies are Relative to the Data Input Frequency, fS) ______________________________________________________________________________________ 23
16-Bit, 500Msps Interpolating and Modulating Dual DAC with CMOS Inputs MAX5895
similar to the first filter and removes the images at 2fS, 6fS, 10fS, etc. Finally, the third filter removes images at 4fS, 12fS, 20fS, etc. Figures 10, 11, and 12 similarly illustrate the spectral responses when using the interpolating filters combined with the digital modulator. When fIM / 2 is chosen as the LO frequency, the input signal is multiplied by [-1, 1] on both channels. This produces images around fIM / 2. The complex image-reject modulation mode is not available for this LO frequency. The outputs of the modulator can be expressed as: I ( t) = A( t) x cos(t) - B( t) x sin(t) Q ( t) = A( t) x sin(t) + B( t) x cos(t) in complex modulation, e+jwt I ( t) = A( t) x cos(t) + B( t) x sin(t) Q ( t) = A( t) x sin(t) + B( t) x cos(t) in complex modulation, e-jwt where = 2 x x fLO. For real modulation, The outputs of the modulator can be expressed as: I ( t) = A( t) x cos(t) Q ( t) = A( t) x cos(t) If more than one MAX5895 is used, their LO phases can be synchronized by simultaneously releasing RESET. This sets the MAX5895 to its predefined initial phase.
Digital Modulator
The MAX5895 features digital modulation at frequencies of fIM / 2 and fIM / 4, where fIM is the data rate at the input to the modulator. fIM equals fDAC in 1x, 2x, and 4x interpolation modes. In 8x interpolation mode, fIM equals fDAC / 2. The output rate of the modulator is always the same as the input data rate to the modulator, fIM. In complex modulation mode, data from the second interpolation filter is frequency mixed with the on-chip in-phase and quadrature (I/Q) local oscillator (LO). Complex modulation provides the benefit of image sideband rejection when combined with an external quadrature modulator commonly found in wireless communication systems. In the fLO = fIM / 4 mode, real or complex modulation can be used. The modulator multiplies successive input data samples by the sequence [1, 0, -1, 0] for a cos(t). The modulator modulates the input signal up to fIM / 4, creating upper and lower images around fIM / 4. The quadrature LO sin(t) is realized by delaying the cos(t) sequence by one clock cycle. Using complex modulation, complex IF is generated. The complex IF combined with an external quadrature modulator provides image rejection. The sign of the LO can be changed to allow the user to select whether the upper or the lower image should be rejected (bit 1 of register 01h).
I-CHANNEL INPUT DATA
Device Reset
The MAX5895 can be reset by holding the RESET pin low for 10ns. This will program the control registers to
I-CHANNEL INPUT DATA
cos(t)
I-CHANNEL OUTPUT DATA
cos(t)
I-CHANNEL OUTPUT DATA
sin(t)
TO FIR3
sin(t)
TO FIR3
sin(t)
sin(t)
Q-CHANNEL INPUT DATA cos(t) (a)
Q-CHANNEL OUTPUT DATA
Q-CHANNEL INPUT DATA cos(t) (b)
Q-CHANNEL OUTPUT DATA
Figure 13. (a) Modulator in Complex Modulation Mode; (b) Modulator in Real Modulation Mode 24 ______________________________________________________________________________________
16-Bit, 500Msps Interpolating and Modulating Dual DAC with CMOS Inputs
their default values in Table 2. During power-on, RESET must be held low until all power supplies have stabilized. Alternately, programming bit 5 of address 00h to a logic-high also resets the MAX5895 after power-up.
Data Clock
The MAX5895 features synchronizers that allow for arbitrary phase alignment between DATACLK and CLKP/CLKN. The DATACLK causes internal switching in the MAX5895 and the phase between DATACLK (input mode) to CLKP/CLKN will influence the images at DATACLK. Optimum image rejection is achieved when DATACLK transitions are aligned with the falling edge of CLKP. Figure 14 shows the image level near DATACLK as a function of the DATACLK (input mode) to CLKP/CLKN phase at 500Msps, 4x interpolation for a 10MHz, -6dBFS output signal.
MAX5895
Power-Down Mode
The MAX5895 features three power-saving modes. Each DAC can be individually powered down through bits 2 and 3 of address 00h. The interpolation filters can also be powered down through bit 4 of address 00h, preserving the output level of each DAC (the DACs remain powered). Powering down both DACs will automatically put the MAX5895 into full power-down, including the interpolation filters.
Clock Interface
The MAX5895 features a flexible differential clock input (CLKP, CLKN) with a separate supply (AV CLK ) to achieve optimum jitter performance. It uses an ultra-low jitter clock to achieve the required noise density. Clock jitter must be less than 0.5psRMS to meet the specified noise density. For that reason, the CLKP/CLKN input source must be designed carefully. The differential clock (CLKN and CLKP) input can be driven from a single-ended or a differential clock source. Differential clock drive is required to achieve the best dynamic performance from the DAC. For single-ended operation, drive CLKP with a low noise source and bypass CLKN to GND with a 0.1F capacitor. The CLKP and CLKN pins are internally biased to AV CLK / 2. This allows the user to AC-couple clock
Applications Information
Frequency Planning
System designers need to take the DAC into account during frequency planning for high-performance applications. Proper frequency planning can ensure that optimal system performance is achieved. The MAX5895 is designed to deliver excellent dynamic performance across wide bandwidths, as required for communication systems and, in particular, for multicarrier applications. As with all DACs, some combinations of output frequency and update rate produce better performance than others. Harmonics are often folded down into the band of interest. Specifically, if the DAC outputs a frequency close to fS / N, the Mth harmonic of the output signal will be aliased down to: N - M f = fS - M x fOUT = fS N Thus, if N (M + 1), the Mth harmonic will be close to the output frequency. SFDR performance of a currentsteering DAC is often dominated by third-order harmonic distortion. If this is a concern, placing the output signal at a different frequency other than fS / 4 should be considered. Common to interpolating DACs are images near the divided clocks. In a DAC configured for 4x interpolation this applies to images around fS / 4 and fS / 2. In a DAC configured for 8x interpolation this applies to images around fS / 8, fS / 4, and fS / 2. Most of these images are not part of the in-band (0 to fDATA / 2) SFDR specification, though they are a consideration for out-of-band (fDATA / 2 - fDAC / 2) SFDR and may depend on the relationship of the DATACLK to DAC update clock (see the Data Clock section). When specifying the output reconstruction filter for other than baseband signals, these images should not be ignored.
fS / 4 IMAGES vs. CLKP/CLKN to DATACLK DELAY fDATA = 125MWps, 4x INTERPOLATION
-50 -60 IMAGE LEVEL (dBc) -70 -80 -90 fS / 4 + fOUT -100 -110 0 2.0 4.0 6.0 8.0 CLKP/CLKN DELAY (ns) fOUT = 10MHz AOUT = -6dBFS fS / 4 - fOUT
Figure 14. Effect of CLKP/CLKN to DATACLK Phase on fS / 4 Images
______________________________________________________________________________________
25
16-Bit, 500Msps Interpolating and Modulating Dual DAC with CMOS Inputs MAX5895
sources directly to the device without external resistors to define the DC level. The input resistance of CLKP and CLKN is 5k. A convenient way to apply a differential signal is with a balun transformer as shown in Figure 15. Alternatively, these inputs may be driven from a CMOS-compatible clock source, however it is recommended to use sine-wave or AC-coupled differential ECL/PECL drive for best dynamic performance.
100nF CLKP MINI-CIRCUITS ADTL1-12 24.9 MAX5895 1:1 RATIO 24.9 100nF CLKN
Output Interface (OUTI, OUTQ)
The MAX5895 outputs complementary currents (OUTIP, OUTIN) and (OUTQP, OUTQN), that can be utilized in a differential configuration. Load resistors convert these two output currents into a differential output voltage. The differential output between OUTIP (OUTQP) and OUTIN (OUTQN) can be converted to a single-ended output using a transformer or a differential amplifier. Figure 16 shows a typical transformer-based application circuit for generation of IF output signals. In this configuration, the MAX5895 operates in differential mode, which reduces even-order harmonics, and increases the available output power. Pay close attention to the transformer core saturation characteristics when selecting a transformer. Transformer core saturation can introduce strong second harmonic distortion,
SINGLE-ENDED IINPUT
Figure 15. Single-Ended-to-Differential Clock Conversion Using a Balun Transformer
50 OUTIP 1:1
VIOUT, SINGLE-ENDED
IDAC 16 OUTIN
100 1:1 50
MAX5895
50 OUTQP QDAC 16 OUTQN 50 100 1:1 1:1
VQOUT, SINGLE-ENDED
Figure 16. Differential-to-Single-Ended Conversion Using Wideband RF Transformers 26 ______________________________________________________________________________________
16-Bit, 500Msps Interpolating and Modulating Dual DAC with CMOS Inputs
especially at low output frequencies and high signal amplitudes. It is recommended to connect the transformer center tap to ground. If a transformer is not used, the outputs must have a resistive termination to ground. Figure 17 shows the MAX5895 output configured for differential DC-coupled mode. The DC-coupled configuration can be used to eliminate waveform distortion due to highpass filter effects. Applications include communication systems employing analog quadrature upconverters and requiring a high-speed DAC for baseband I/Q synthesis. If a single-ended DC-coupled unipolar output is desirable, OUTIP (OUTQP) should be selected as the output, and connect OUTIN (OUTQN) to ground. Using the MAX5895 output single-ended is not recommended because it introduces additional noise and distortion. The distortion performance of the DAC also depends on the load impedance. The MAX5895 is optimized for a 50 double termination. It can be used with a transformer output as shown in Figure 16 or just one 25 resistor from each output to ground and one 50 resistor between the outputs (Figure 17). Higher output termination resistors may be used, as long as each output voltage does not exceed +1V with respect to GND, but at the cost of degraded distortion performance and increased output noise voltage.
MAX5895
25 OUTIP
IDAC 16 OUTIN
50
25
MAX5895
25 OUTQP QDAC 16 OUTQN 25 50
Figure 17. The DC-Coupled Differential Output Configuration
______________________________________________________________________________________
27
16-Bit, 500Msps Interpolating and Modulating Dual DAC with CMOS Inputs MAX5895
Reference Input/Output
The MAX5895 supports operation with the on-chip 1.2V bandgap reference or an external reference voltage source. REFIO serves as the input for an external, lowimpedance reference source, and as the output if the DAC is operating with the internal reference. For stable operation with the internal reference, REFIO should be decoupled to GND with a 1F capacitor. REFIO must be buffered with an external amplifier, if heavy loading is required, due to its 10k output resistance. Alternatively, apply a temperature-stable external reference to REFIO (Figure 18). The internal reference is overdriven by the external reference. For improved accuracy and drift performance, choose a fixed output voltage reference such as the MAX6520 bandgap reference. The MAX5895's reference circuit (Figure 19) employs a control amplifier, designed to regulate the full-scale current IOUT for the differential current outputs of the DAC. The output current can be calculated as: IOUTFS = 32 x IREFIO - 1LSB IOUTFS = 32 x IREFIO - (IOUT / 216) where IREFIO is the reference output current (IREFIO = VREFIO / RSET) and IOUT is the full-scale output current of the DAC. Located between FSADJ and DACREF, RSET is the reference resistor, which determines the amplifier's output current for the DAC. Use Table 5 for a matrix of different IOUTFS and RSET selections.
1.2V REFERENCE MAX5895 10k EXTERNAL 1.25V REFERENCE REFIO 1F 1F REFIO
1.2V REFERENCE MAX5895 10k
FSADJ IREF RSET DACREF
CURRENTSOURCE ARRAY DAC
FSADJ IREF RSET DACREF
CURRENTSOURCE ARRAY DAC
Figure 18. Typical External Reference Circuit
Figure 19. MAX5895 Internal Reference Architecture
Table 5. IOUTFS and RSET Selection Matrix Based on a Typical 1.20V Reference Voltage
FULL-SCALE CURRENT IOUTFS (mA) 2 5 10 15 20 REFERENCE CURRENT IREF (A) 62.50 156.26 312.50 468.75 625.00 19.2k 7.68k 3.84k 2.56k 1.92k RSET () CALCULATED 1% EIA STD 19.1k 7.5k 3.83k 2.55k 1.91k OUTPUT VOLTAGE VIOUTP/N* (mVP-P) 100 250 500 750 1000
*Terminated into a 50 load. 28 ______________________________________________________________________________________
16-Bit, 500Msps Interpolating and Modulating Dual DAC with CMOS Inputs
Power Supplies, Bypassing, Decoupling, and Layout
Grounding and power-supply decoupling strongly influence the MAX5895 performance. Unwanted digital crosstalk can couple through the input, reference, power-supply, and ground connections, which can affect dynamic specifications like signal-to-noise ratio or spurious-free dynamic range. In addition, electromagnetic interference (EMI) can either couple into or be generated by the MAX5895. Observe the grounding and power-supply decoupling guidelines for highspeed, high-frequency applications. Follow the powersupply and filter configuration guidelines to achieve optimum dynamic performance. Using a multilayer printed circuit (PC) board with separate ground and power-supply planes, run high-speed signals on lines directly above the ground plane. Since the MAX5895 has separate analog and digital sections, the PC board should include separate analog and digital ground sections with only one point connecting the three planes at the exposed paddle under the MAX5895. Run digital signals above the digital ground plane and analog/clock signals above the analog/clock ground plane. Keep digital signals as far away from sensitive analog inputs, reference lines, and clock inputs as practical. Use a symmetric design of clock input and the analog output lines to minimize 2nd-order harmonic distortion components, thus optimizing the dynamic performance of the DAC. Keep digital signal paths short and run lengths matched to avoid propagation delay and data skew mismatches. The MAX5895 requires five separate power-supply inputs for the analog (AVDD1.8 and AVDD3.3), digital (DVDD1.8 and DVDD3.3), and clock (AVCLK) circuitry. Decouple each voltage supply pin with a separate 0.1F capacitor as close to the device as possible and with the shortest possible connection to the appropriate ground plane. Minimize the analog and digital load capacitances for optimized operation. Decouple all power-supply voltages at the point they enter the PC board with tantalum or electrolytic capacitors. Ferrite beads with additional decoupling capacitors forming a pi-network could also improve performance. The exposed paddle (EP) MUST be soldered to the ground. Use multiple vias, an array of at least 4 x 4 vias, directly under the EP to provide a low thermal and electrical impedance path for the IC.
Static Performance Parameter Definitions
Integral Nonlinearity (INL)
Integral nonlinearity is the deviation of the values on an actual transfer function from either a best straight-line fit (closest approximation to the actual transfer curve) or a line drawn between the end points of the transfer function, once offset and gain errors have been nullified. For a DAC, the deviations are measured at every individual step.
MAX5895
Differential Nonlinearity (DNL)
Differential nonlinearity is the difference between an actual step height 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.
Offset Error
The offset error is the difference between the ideal and the actual offset current. For a DAC, the offset point is the average value at the output for the two midscale digital input codes with respect to the full-scale of the DAC. This error affects all codes by the same amount.
Gain Error
A gain error is the difference between the ideal and the actual full-scale output voltage on the transfer curve, after nullifying the offset error. This error alters the slope of the transfer function and corresponds to the same percentage error in each step.
Dynamic Performance Parameter Definitions
Settling Time
The settling time is the amount of time required from the start of a transition until the DAC output settles its new output value to within the specified accuracy.
Noise Spectral Density
The DAC output noise is the sum of the quantization noise and thermal noise. Noise spectral density is the noise power in 1Hz bandwidth, specified in dBFS/Hz.
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 output (RMS value) to the RMS quantization error (residual error). The ideal, theoretical maximum SNR can be derived from the DAC's resolution (N bits): SNRdB = 6.02dB x N + 1.76dB
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29
16-Bit, 500Msps Interpolating and Modulating Dual DAC with CMOS Inputs MAX5895
However, noise sources such as thermal noise, reference noise, clock jitter, etc. affect the ideal reading. Therefore, SNR is computed by taking the ratio of the RMS signal to the RMS noise, which includes all spectral components minus the fundamental, the first four harmonics, and the DC offset.
Two-/Four-Tone Intermodulation Distortion (IMD)
The two-tone IMD is the ratio expressed in dBc (or dBFS) of the worst 3rd-order (or higher) IMD products to either output tone.
Spurious-Free Dynamic Range (SFDR)
SFDR is the ratio of the RMS amplitude of the carrier frequency (maximum signal components) to the RMS value of their next largest distortion component. SFDR is usually measured in dBc and with respect to the carrier frequency amplitude or in dBFS with respect to the DAC's full-scale range. Depending on its test condition, SFDR is observed within a predefined window or to Nyquist.
Adjacent Channel Leakage Power Ratio (ACLR)
Commonly used in combination with WCDMA (wideband code-division multiple-access), ACLR reflects the leakage power ratio in dB between the measured powers within a channel relative to its adjacent channel. ACLR provides a quantifiable method of determining out-of-band spectral energy and its influence on an adjacent channel when a bandwidth-limited RF signal passes through a nonlinear device.
Pin Configuration
TOP VIEW
AVDD1.8 AVDD3.3 AVDD3.3 AVDD3.3 AVDD1.8 OUTQN OUTQP FSADJ
51 DACREF 50 REFIO 49 RESET 48 CS 47 SCLK 46 SDI 45 SDO 44 DVDD3.3 43 B0 42 B1 41 B2 40 B3 39 B4 38 B5 37 DVDD1.8 36 B6 35 B7
OUTIP
OUTIN
AVCLK
GND
GND
GND
GND
GND DVDD1.8
68
67 66 65 64
63 62 61 60 59 58
57 56 55 54 53 52
CLKP CLKN N.C. N.C. N.C. DVDD1.8 A15 A14 A13
1 2 3 4 5 6 7 8 9
EXPOSED PADDLE
MAX5895
A12 10 A11 11 A10 12 DVDD3.3 13 DATACLK 14 A9 15 A8 16 A7 17
18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34
A5
A4
DATACLK/B14
SELIQ/B15
B13
B12
B11
DVDD1.8
B10
A3
A2
A1
A0
GND
B9
A6
QFN
30
______________________________________________________________________________________
B8
16-Bit, 500Msps Interpolating and Modulating Dual DAC with CMOS Inputs MAX5895
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.)
PACKAGE OUTLINE, 68L QFN, 10x10x0.9 MM 1 C 21-0122 2
______________________________________________________________________________________
68L QFN.EPS
31
16-Bit, 500Msps Interpolating and Modulating Dual DAC with CMOS Inputs MAX5895
Package Information (continued)
(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.)
PACKAGE OUTLINE, 68L QFN, 10x10x0.9 MM 1 C 21-0122 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.
32 ____________________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.

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