CMOS Dual 8-Bit a Buffered Multiplying DAC AD7628 FEATURES FUNCTIONAL BLOCK DIAGRAM On-Chip Latches for Both DACs +12 V to +15 V Operation DACs Matched to 1% Four Quadrant Multiplication TTL/CMOS Compatible from +12 V to +15 V Latch Free (Protection Schottkys not Required) APPLICATIONS Disk Drives Programmable Filters X-Y Graphics Gain/Attenuation GENERAL DESCRIPTION PRODUCT HIGHLIGHTS The AD7628 is a monolithic dual 8-bit digital/analog converter 1. DAC to DAC matching: since both of the AD7628 DACs featuring excellent DAC-to-DAC matching. It is available in are fabricated at the same time on the same chip, precise small 0.3 wide 20-pin DIPs and in 20-terminal surface mount matching and tracking between DAC A and DAC B is inher- packages. ent. The AD7628s matched CMOS DACs make a whole new range of applications circuits possible, particularly in the Separate on-chip latches are provided for each DAC to allow audio, graphics and process control areas. easy microprocessor interface. 2. Small package size: combining the inputs to the on-chip Data is transferred into either of the two DAC data latches via a DAC latches into a common data bus and adding a DAC A/ common 8-bit TTL/CMOS compatible input port. Control in- DAC B select line has allowed the AD7628 to be packaged in put DAC A/DAC B determines which DAC is to be loaded. a small 20-pin 0.3 wide DIP, 20-pin SOIC, 20-terminal The AD7628s load cycle is similar to the write cycle of a ran- PLCC and 20-terminal LCC. dom access memory, and the device is bus compatible with most 8-bit microprocessors, including 6502, 6809, 8085, Z80. 3. TTL-Compatibility: All digital inputs are TTL-compatible over a +12 V to +15 V power supply range. The device operates from a +12 V to +15 V power supply and is TTL-compatible over this range. Power dissipation is a low 20 mW. Both DACs offer excellent four quadrant multiplication charac- teristics with a separate reference input and feedback resistor for each DAC. REV. A Information furnished by Analog Devices is believed to be accurate and reliable. However, no responsibility is assumed by Analog Devices for its One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A. use, nor for any infringements of patents or other rights of third parties Tel: 617/329-4700 World Wide Web Site: (V = +10.8 V to +15.75 V, V A = V B = +10 V OUT A = OUT B = 0 V unless DD REF REF AD7628SPECIFICATIONS otherwise noted) T = 408CT = 558C A A 1 1 Parameter T = +258C to +858C to +1258C Units Test Conditions/Comments A 2 STATIC PERFORMANCE Resolution 8 8 8 Bits Relative Accuracy 1/2 1/2 1/2 LSB max This is an Endpoint Linearity Specification Differential Nonlinearity 1 1 l LSB max All Grades Guaranteed Monotonic Over Full Operating Temperature Range Gain Error 2 3 3 LSB max Measured Using Internal RFB A and RFB B. Both DAC Latches Loaded with 11111111. Gain Error is Adjustable Using Circuits of Figures 4 and 5. 3 Gain Temperature Coefficient Gain/Temperature 0.0035 0.0035 %/C max Output Leakage Current OUT A (Pin 2) 50 200 200 nA max DAC Latches Loaded with 00000000 OUT B (Pin 20) 50 200 200 nA max Input Resistance (V A, VB) 88 8k min Input Resistance TC = 300 ppm/C, Typical REF REF 15 15 15 k max Input Resistance is 11 k V A/V B Input Resistance REF REF Match 1 1 1 % max 4 DIGITAL INPUTS Input High Voltage (V ) 2.4 2.4 2.4 V min IH Input Low Voltage (V ) 0.8 0.8 0.8 V max IL Input Current (I ) 1 10 10 A max V = 0 or V IN IN DD Input Capacitance DB0DB7 10 10 10 pF max WR, CS, DACA/DACB 15 15 15 pF max 3 SWITCHING CHARACTERISTICS See Timing Diagram Chip Select to Write Set Up Time (t ) 160 160 210 ns min CS Chip Select to Write Hold Time (t ) 10 10 10 ns min CH DAC Select to Write Set Up Time (t ) 160 160 210 ns min AS DAC Select to Write Hold Time (t ) 10 10 10 ns min AH Data Valid to Write Set Up Time (t ) 160 160 210 ns min DS Data Valid to Write Hold Time (t ) 10 10 10 ns min DH Write Pulse Width (t ) 150 170 210 ns min WR POWER SUPPLY See Figure 3 I , K Grade 2 2 mA All Digital Inputs V or V DD IL IH B, T Grades 2 2.5 2.5 mA All Digital Inputs V or V IL IH All Grades 100 500 500 A All Digital Inputs 0 V or V DD Specifications subject to change without notice. AC PERFORMANCE CHARACTERISTICS These characteristics are included for Design Guidance only and are not subject to test. V = +10.8 V to +15.75 V. (Measured Using Recommended PC Board Layout (Figure 7) and AD644 as Output Amplifiers) DD T = 408CT = 558C A A 1 1 1 Parameter T = +258C to +858C to +1258C Units Test Conditions/Comments A DC SUPPLY REJECTION (GAIN/V ) 0.01 0.02 0.02 % per % max V = 5% DD DD CURRENT SETTLING TIME 350 400 400 ns max To 1/2 LSB OutA/OutB Load = 100 . WR = CS = 0 V. DB0DB7 = 0 V to V or V to 0 V DD DD DIGITAL-TO-ANALOG GLITCH IMPULSE 330 nV sec typ For Code Transition 00000000 to 11111111 OUTPUT CAPACITANCE C A 25 25 25 pF max DAC Latches Loaded with 00000000 OUT C B 25 25 25 pF max OUT C A 60 60 60 pF max DAC Latches Loaded with 11111111 OUT C B 60 60 60 pF max OUT AC FEEDTHROUGH V A to OUT A 70 65 65 dB max V A, V B = 20 V p-p Sine Wave REF REF REF V B to OUT B 70 65 65 dB max 10 kHz REF CHANNEL-TO-CHANNEL ISOLATION Both DAC Latches Loaded with 11111111. V A to OUT B 80 dB typ V A = 20 V p-p Sine Wave 10 kHz REF REF V B = 0 V See Figure 6. REF V B to OUTA 80 dB typ V B = 20 V p-p Sine Wave 10 kHz REF REF V A = 0 V See Figure 6. REF DIGITAL CROSSTALK 60 nV sec typ Measured for Code Transition 00000000 to 11111111 HARMONIC DISTORTION 85 dB typ V = 6 V rms 1 kHz IN NOTES 1 Temperature Ranges are K Version 40C to +85C B Version 40C to +85C T Version 55C to +125C. 2 Specification applies to both DACs in AD7628. 3 Guaranteed by design but not production tested. 4 Logic inputs are MOS Gates. Typical input current (+25C) is less than 1 nA. Specifications subject to change without notice. 2 REV. A