® DAC811 For most current data sheet and other product information, visit www.burr-brown.com Microprocessor-Compatible 12-BIT DIGITAL-TO-ANALOG CONVERTER FEATURES ● SINGLE INTEGRATED CIRCUIT CHIP ● MICROCOMPUTER INTERFACE: DOUBLE-BUFFERED LATCH ● VOLTAGE OUTPUT: ±10V, ±5V, +10V ● MONOTONICITY GUARANTEED OVER TEMPERATURE ● ±1/2LSB MAXIMUM NONLINEARITY OVER TEMPERATURE ● GUARANTEED SPECIFICATIONS AT ±12V AND ±15V SUPPLIES ● TTL/5V CMOS-COMPATIBLE LOGIC INPUTS DESCRIPTION The DAC811 is a complete, single-chip integratedcircuit, microprocessor-compatible, 12-bit digital-toanalog converter. The chip combines a precision voltage reference, microcomputer interface logic, and double-buffered latch, in a 12-bit D/A converter with a voltage output amplifier. Fast current switches and a laser-trimmed thin-film resistor network provide a highly accurate and fast D/A converter. Input gating logic is designed so that loading the last nibble or byte of data can be accomplished simultaneously with the transfer of data (previously stored in adjacent latches) from adjacent input latches to the D/A latch. This feature avoids spurious analog output values while using an interface technique that saves computer instructions. The DAC811 is laser trimmed at the wafer level and is specified to ±1/4LSB maximum linearity error (B, K, and S grades) at 25°C and ±1/2LSB maximum over the temperature range. All grades are guaranteed monotonic over the specification temperature range. The DAC811 is available in six performance grades and three package types. DAC811J and K are specified over the temperature ranges of 0°C to +70°C; DAC811A and B are specified over –25°C to +85°C; DAC811R and S are specified over –55°C to +125°C. DAC811J and K are packaged in a reliable 28-pin plastic DIP or plastic SOIC package, while DAC811A, B, R and S are available in a 28-pin 0.6" wide dualinline hermetically sealed ceramic side-brazed package (H package). Microcomputer interfacing is facilitated by a doublebuffered latch. The input latch is divided into three 4-bit nibbles to permit interfacing to 4-, 8-, 12-, or 16-bit buses and to handle right-or left-justified data. The 12-bit data in the input latches is transferred to the D/A latch to hold the output value. 4 MSBs 4 LSBs SJ Input Latch Input Latch Input Latch RF 10V D/A Latch RF 12-Bit D/A Converter RBPO Voltage Reference VOUT BPO International Airport Industrial Park • Mailing Address: PO Box 11400, Tucson, AZ 85734 • Street Address: 6730 S. Tucson Blvd., Tucson, AZ 85706 • Tel: (520) 746-1111 Twx: 910-952-1111 • Internet: http://www.burr-brown.com/ • Cable: BBRCORP • Telex: 066-6491 • FAX: (520) 889-1510 • Immediate Product Info: (800) 548-6132 ® © 1983 Burr-Brown Corporation PDS-503K 1 Printed in U.S.A. January, 2000 DAC811 SPECIFICATIONS At TA = +25°C. ±VCC = 12V or 15V, unless otherwise noted. DAC811AH, JP, JU PARAMETER MIN DIGITAL INPUT Resolution Codes(1) Digital Inputs Over Temperature Range(2) VIH VIL IIH, VI = +2.7V IIL, VI = +0.4V Digital Interface Timing Over Temperature Range tWP, WR Pulse Width tAW1, NX and LDAC Valid to End of WR tDW, Data Valid to End of WR tDH, Data Valid Hold Time TYP MAX DAC811BH, KP, KU MIN TYP MAX ✻ ✻ +15 +0.8 +10 ±20 ✻ ✻ ✻ ✻ ✻ ✻ ✻ ✻ ✻ 50 50 80 0 ±1/8 ±1/4 ✻ ✻ ✻ ✻ ✻ ✻ ±1/4 ±1/2 ✻ ✻ DRIFT (Over Specification Temperature Range) Gain Unipolar Offset Bipolar Zero Linearity Error Over Temperature Range Monotonicity Over Temperature Range ±10 ±5 ±5 ±1/2 Guaranteed ±10 ±5 ±5 ±1/4 ✻ ✻ ✻ ✻ ✻ SETTLING TIME(6) (to within ±0.01% of FSR of Final Value; 2kΩ load) For Full Scale Range Change, 20V Range 3 4 10V Range 3 4 For 1LSB Change at Major Carry(7) 1 Slew Rate(6) 8 12 REFERENCE VOLTAGE Voltage Source Current Available for External Loads Temperature Coefficient Short Circuit to Common Duration POWER SUPPLY REQUIREMENTS Voltage: +VCC –VCC VDD Current (no load): +VCC –VCC VDD Potential at DCOM with Respect to ACOM(9) Power Dissipation ±5 ✻ +11.4 –11.4 +4.5 ±20 ±7 ±7 ±1/2 ±15 ±5 ±5 ±1/2 ✻ ✻ ✻ ✻ ✻ ✻ ✻ ✻ ✻ ✻ ✻ +6.4 ±10 Indefinite ±30 +15 –15 +5 +16 –23 +8 ±0.5 625 +16.5 –16.5 +5.5 +25 –35 +15 ✻ ✻ ✻ ✻ ✻ 800 ✻ ✻ ±10 ✻ ±20 ✻ ✻ ✻ ✻ ✻ ✻ ✻ ✻ ✻ ✻ ✻ ✻ ✻ ✻ ✻ ✻ ✻ ✻ TEMPERATURE RANGE Specification: J, K A, B R, S 0 –25 –65 +70 +85 +150 ✻ ✻ ✻ ✻ ✻ ✻ Storage: J, K A, B, R, S –60 –65 +100 +150 ✻ ✻ ✻ ✻ ✻ ✻ ✻ ✻ VDC VDC µA µA ns ns ns ✻ ✻ ✻ % of FSR/%VCC % of FSR/%VCC % of FSR/%VDD ±30 ±10 ±10 ±3/4 ±15 ±5 ±5 ±1/4 ✻ ±30 ±7 ±7 ±1/2 ppm/°C ppm of FSR/°C ppm of FSR/°C LSB ✻ ✻ ✻ ✻ ✻ ✻ ✻ ✻ µs µs µs V/µs ✻ ✻ ✻ ✻ ✻ ✻ V V mA Ω ✻ ✻ ✻ ✻ ✻ ±10 ✻ ±30 ✻ ✻ ✻ ✻ ✻ ✻ ✻ ✻ ✻ ✻ ✻ ✻ ✻ ✻ ✻ ✻ ✻ ✻ ✻ ✻ +125 ✻ ✻ ✻ ✻ ✻ ✻ ✻ ✻ ✻ ✻ ✻ ✻ –55 ✻ ✻ Bits LSB LSB % % of FSR(5) ✻ ✻ ✻ ✻ ✻ ±1/4 ±1/2 ✻ ✻ ✻ ✻ UNITS ±1/8 ±1/4 ✻ ✻ ✻ ✻ ✻ ✻ ✻ ✻ ✻ MAX ✻ ✻ ✻ ✻ ±1/2 ±3/4 ✻ ✻ ✻ ✻ +6.3 ✻ ✻ ✻ ✻ ±1/4 ±1/2 ✻ ✻ ✻ ✻ ✻ ✻ ✻ 0.2 Indefinite +6.2 +2 ✻ ✻ ✻ ✻ 0 to +10 ±5, ±10 TYP ✻ ✻ ✻ ✻ +10 ±1/4 ±1/2 ±1/2 ±3/4 ±0.1 ±0.2 ±0.05 ±0.15 Guaranteed ±0.001 ±0.003 ±0.002 ±0.006 ±0.0005 ±0.0015 ±30 ±10 ±10 ±3/4 DAC811SH MAX MIN ✻ ✻ ACCURACY Linearity Error Differential Linearity Error Gain Error(3) Offset Error(3, 4) Monotonicity Power Supply Sensitivity: +VCC –VCC VDD ANALOG OUTPUT Voltage Range (±VCC = 15V)(8): Unipolar Bipolar Output Current Output Impedance (at DC) Short Circuit to Common Duration TYP ✻ 12 USB, BOB +2 0 DAC811RH MIN ✻ ✻ ✻ ✻ ±10 ✻ ±20 V mA ppm/°C ✻ ✻ ✻ ✻ ✻ ✻ ✻ ✻ ✻ ✻ ✻ ✻ ✻ ✻ VDC VDC VDC mA mA mA V mW ✻ ✻ ✻ ✻ ✻ ✻ °C °C °C °C °C °C ✻ ✻ Specification same as DAC811AH. NOTES: (1) USB = unipolar straight binary; BOB = bipolar offset binary. (2) TTL, LSTTL and 54/74 HC compatible. (3) Adjustable to zero with external trim potentiometer. (4) Error at input code 00016 for both unipolar and bipolar ranges. (5) FSR means full scale range and is 20V for the ±10V range. (6) Maximum represents the 3σ limit. Not 100% tested for this parameter. (7) At the major carry, 7FF16 to 80016 and 80016 to 7FF16. (8) Minimum supply voltage required for ±10V output swing is ±13.5V. Output swing for ±11.4V supplies is at least –8V to +8V. (9) The maximum voltage at which ACOM and DCOM may be separated without affecting accuracy specifications. ® DAC811 2 PIN DESCRIPTIONS PIN ABSOLUTE MAXIMUM RATINGS NAME FUNCTION 1 +VDD Logic supply, +5V. 2 WR Write, command signal to load latches. Logic low loads latches. 3 LDAC Load D/A converter, enables WR to load the D/A latch. Logic low enables. 4 NA Nibble A, enables WR to load input latch A (the most significant nibble). Logic low enables. 5 NB Nibble B, enables WR to load input latch B. Logic low enables. 6 NC Nibble C, enables WR to load input latch C (the least significant nibble). Logic low enables. 7 D11 Data bit 12, MSB, positive true. 8 D10 Data bit 11. 9 D9 Data bit 10. 10 D8 Data bit 9. 11 D7 Data bit 8. 12 D6 Data bit 7. 13 D5 Data bit 6. +VCC ................................................................................................................................ 0 to +18V –VCC to ACOM .......................................................................... 0 to –18V VDD to DCOM .............................................................................. 0 to +7V VDD to ACOM ...................................................................................... ±7V ACOM to DCOM .................................................................................. ±7V Digital Inputs (Pins 2–14, 16–19) to DCOM ...................... –0.4V to +18V External Voltage Applied to 10V Range Resistor ............................ ±12V Ref Out ............................................................. Indefinite Short to ACOM External Voltage Applied to DAC Output ................................ –5V to +5V Power Dissipation ........................................................................ 1000mW Lead Temperature (soldering, 10s) ............................................... +300°C Max Junction Temperature ............................................................ +165°C Thermal Resistance, θJ-A: Plastic DIP and SOIC ....................... 100°C/W Ceramic DIP .................................................................................. 65°C/W NOTE: Stresses above those listed above may cause permanent damage to the device. Exposure to absolute maximum conditions for extended periods may affect device reliability. ELECTROSTATIC DISCHARGE SENSITIVITY 14 D4 Data bit 5. 15 DCOM Digital common, VDD supply return. 16 D0 Data bit 1, LSB. 17 18 19 20 21 22 23 24 25 26 27 D1 D2 D3 +VCC –VCC Gain Adj ACOM VOUT 10V Range SJ BPO Data bit 2. Data bit 3. Data bit 4. Analog supply input, +15V or +12V. Analog supply input, –15V or –12V. To externally adjust gain. Analog common, ±VCC supply return. D/A converter voltage output. Connect to pin 24 for 10V range. Summing junction of output amplifier. Bipolar offset. Connect to pin 26 for bipolar operation. 28 Ref Out 6.3V reference output. This integrated circuit can be damaged by ESD. Burr-Brown recommends that all integrated circuits be handled with appropriate precautions. Failure to observe proper handling and installation procedures can cause damage. ESD damage can range from subtle performance degradation to complete device failure. Precision integrated circuits may be more susceptible to damage because very small parametric changes could cause the device not to meet its published specifications. PACKAGE/ORDERING INFORMATION PRODUCT MINIMUM RELATIVE ACCURACY (LSB) DIFFERENTIAL LINEARITY (LSB) DAC811AH DAC811JP DAC811JU ±1/2 LSB ±1/2 LSB ±1/2 LSB 3/4 3/4 3/4 " DAC811KP DAC811KU PACKAGE PACKAGE DRAWING NUMBER SPECIFICATION TEMPERATURE RANGE ORDERING NUMBER(1) TRANSPORT MEDIA CerDIP-28 DIP-28 SOIC-28 149 215 217 –25°C to +85°C 0°C to +70°C 0°C to +70°C DAC811AH DAC811JP DAC811JU Rails Rails Rails DAC811JU/1K DAC811KP DAC811KU Tape and Reel Rails Rails " " " " " ±1/4 LSB ±1/4 LSB 1/2 1/2 DIP-28 SOIC-28 215 217 0°C to +70°C 0°C to +70°C NOTE: (1) Models with a slash (/) are available only in Tape and Reel in the quantities indicated (e.g., /1K indicates 1000 devices per reel). Ordering 1000 pieces of “DAC811JU/1K” will get a single 1000-piece Tape and Reel. The information provided herein is believed to be reliable; however, BURR-BROWN assumes no responsibility for inaccuracies or omissions. BURR-BROWN assumes no responsibility for the use of this information, and all use of such information shall be entirely at the user’s own risk. Prices and specifications are subject to change without notice. No patent rights or licenses to any of the circuits described herein are implied or granted to any third party. BURR-BROWN does not authorize or warrant any BURR-BROWN product for use in life support devices and/or systems. ® 3 DAC811 TIMING DIAGRAMS Write Cycle #2 Load second rank from first rank: NA , NB , N C = 1 Write Cycle #1 Load first rank from Data Bus: LDAC = 1 tAW tAW LDAC N A , NB , N C tWP tDW WR DB11 –DB0 tSET tWP tDH WR ±1/2LSB DISCUSSION OF SPECIFICATIONS DRIFT Gain drift is a measure of the change in the full scale range (FSR) output over the specification temperature range. Drift is expressed in parts per million per degree centigrade (ppm/°C). Gain drift is established by testing the full scale range value (e.g., +FS minus –FS) at high temperature, +25°C, and low temperature, calculating the error with respect to the +25°C value, and dividing by the temperature change. INPUT CODES The DAC811 accepts positive-true binary input codes. DAC811 may be connected by the user for any one of the following codes: USB (unipolar straight binary), BOB (bipolar offset binary) or, using an external inverter on the MSB line, BTC (binary two’s complement). See Table I. DIGITAL INPUT Unipolar offset drift is a measure of the change in output with all 0s on the input over the specification temperature range. Offset is measured at high temperature, +25°C, and low temperature. The offset drift is the maximum change in offset referred to the +25°C value, divided by the temperature change. It is expressed in parts per million of full scale range per degree centigrade (ppm of FSR/°C). ANALOG OUTPUT USB Unipolar Straight Binary BOB Bipolar Offset Binary BTC(1) Binary Two’s Complement + Full Scale + 1/2 Full Scale + 1/2 Full Scale – 1LSB Zero + Full Scale Zero –1LSB – Full Scale –1LSB – Full Scale + Full Scale Zero Bipolar zero drift is measured at a digital input of 80016, the code that gives zero volts output for bipolar operation. NOTE: (1) Invert MSB of the BOB code with external inverter to obtain BTC code. SETTLING TIME Settling time is the total time (including slew time) for the output to settle within an error band around its final value after a change in input. Three settling times are specified to ±0.01% of full scale range (FSR): two for maximum full scale range changes of 20V and 10V, and one for a 1LSB change. The 1LSB change is measured at the major carry (7FF16 to 80016 and 80016 to 7FF16), the input transition at which worst-case settling time occurs. MSB LSB ↓ ↓ 111111111111 100000000000 011111111111 000000000000 TABLE I. Digital Input Codes. LINEARITY ERROR Linearity error as used in D/A converter specifications by Burr-Brown is the deviation of the analog output from a straight line drawn between the end points (inputs all 1s and all 0s). The DAC811 linearity error is specified at ±1/4LSB (max) at +25°C for B and K grades, and ±1/2LSB (max) for A, J, and R grades. REFERENCE SUPPLY DAC811 contains an on-chip 6.3V reference. This voltage (pin 28) has a tolerance of ±0.1V. The reference output may be used to drive external loads, sourcing at least 2mA. This current should be constant for best performance of the D/A converter. DIFFERENTIAL LINEARITY ERROR Differential linearity error (DLE) is the deviation from a 1LSB output change from one adjacent state to the next. A DLE specification of 1/2LSB means that the output step size can range from 1/2LSB to 3/2LSB when the input changes from one state to the next. Monotonicity requires that DLE be less than 1LSB over the temperature range of interest. POWER SUPPLY SENSITIVITY Power supply sensitivity is a measure of the effect of a power supply change on the D/A converter output. It is defined as a percent of FSR output change per percent of change in either the positive, negative, or logic supply voltages about the nominal voltages. Figure 1 shows typical power supply rejection versus power supply ripple frequency. MONOTONICITY A D/A converter is monotonic if the output either increases or remains the same for increasing digital inputs. All grades of DAC811 are monotonic over their specification temperature range. ® DAC811 4 The D/A latch is controlled by LDAC and WR. LDAC and WR are internally NORed so that the latches transmit data to the D/A switches when both LDAC and WR are at logic 0. When either LDAC or WR are at logic 1, the data is latched in the D/A latch and held until LDAC and WR go to logic 0. Percent of FSR per Percent of Change of Power Supply Voltage 1 –VCC 0.1 V DD 0.01 All latches are level-triggered. Data present when the control signals are logic 0 will enter the latch. When any one of the control signals returns to logic 1, the data is latched. Table II is a truth table for all latches. +VCC 0.001 0.0001 10 100 1k 10k 1M 100k Frequency (Hz) FIGURE 1. Power Supply Rejection vs Power Supply Ripple Frequency. WR NA NB NC LDAC 1 0 0 0 0 0 X 0 1 1 1 0 X 1 0 1 1 0 X 1 1 0 1 0 X 1 1 1 0 0 OPERATION No operation Enables input latch 4MSBs Enables input latch 4 middle bits Enables input latch 4LSBs Loads D/A latch from input latches Makes all latches transparent “X” = Don’t care. OPERATION TABLE II. DAC813 Interface Logic Truth Table. DAC811 is a complete single IC chip 12-bit D/A converter. The chip contains a 12-bit D/A converter, voltage reference, output amplifier, and microcomputer-compatible input logic as shown in Figure 2. GAIN AND OFFSET ADJUSTMENTS Figures 3 and 4 illustrate the relationship of offset and gain adjustments to unipolar and bipolar D/A converter output. INTERFACE LOGIC Input latches A, B, and C hold data temporarily while a complete 12-bit word is assembled before loading into the D/A register. This double-buffered organization prevents the generation of spurious analog output values. Each register is independently addressable. OFFSET ADJUSTMENT For unipolar (USB) configurations, apply the digital input code that should produce zero voltage output, and adjust the offset potentiometer for zero output. For bipolar (BOB, BTC) configurations, apply the digital input code that should produce the maximum negative output voltage and adjust the offset potentiometer for minus full scale voltage. Example: If the full scale range is connected for 20V, the maximum negative output voltage is –10V. See Table III for corresponding codes. These input latches are controlled by NA, NB, NC, and WR. NA, NB, and NC are internally NORed with WR so that the input latches transmit data when both NA (or NB, NC ) and WR are at logic 0. When either NA, (NB, NC ) or WR go to logic 1, the input data is latched into the input registers and held until both NA (or NB, NC ) and WR go to logic 0. MSB D11 7 WR 8 9 D8 D7 10 11 12 13 D4 D3 14 19 D0 18 17 16 RBPO 2 4-Bit Latch, A NA 4 NB 5 LSB 4-Bit Latch, B 4-Bit Latch, C 27 BPO 26 SJ 25 10V Range 24 VOUT 23 ACOM RF NC 6 LDAC 3 12-Bit D/A Latch RF 12-Bit D/A Converter Reference Ref Out 28 FIGURE 2. DAC811 Block Diagram. ® 5 DAC811 ±12V OPERATION + Full Scale The DAC811 is fully specified for operation on ±12V power supplies. However, in order for the output to swing to ±10V, the power supplies must be ±13.5V or greater. When operating with ±12VB supplies, the output swing should be restricted to ±8V in order to meet specifications. Range of Gain Adjust Full Scale Range Analog Output 1LSB Range of Offset Adj. LOGIC INPUT COMPATIBILITY The DAC811 digital inputs are TTL, LSTTL, and 54/74HC CMOS-compatible over the operating range of VDD. The input switching threshold remains at the TLL threshold over the supply range. Gain Adjust Rotates the Line All Bits Logic 0 All Bits Logic 1 The logic input current over temperature is low enough to permit driving the DAC811 directly from the outputs of 4000B and 54/74C CMOS devices. Digital Input Offset Adjust Translates the Line Resistors of 47Ω should be placed in series with D0 through D11, WR, NA, NB, NC and LDAC if edges are <10ns or if the logic input is driven below ground by undershoot. FIGURE 3. Relationship of Offset and Gain Adjustments for a Unipolar D/A Converter. INSTALLATION + Full Scale POWER SUPPLY CONNECTIONS For optimum performance and noise rejection, power supply decoupling capacitors should be added as shown in Figure 5. Analog Output 1LSB Range of Gain Adjust Full Scale Range All Bits Logic 0 Bipolar V Offset These capacitors (1µF tantalum recommended) should be located close to the DAC811. Gain Adjust Rotates the Line MSB on All Others Off All Bits Logic 1 Range of Offset Adjust VDD – Full Scale Offset Adj. Translates the Line ≈ ±0.4% 1µF 1 28 V DD 2 BPO 27 3 Summing Junction 26 Digital Input 4 FIGURE 4. Relationship of Offset and Gain Adjustments for a Bipolar D/A Converter. ANALOG OUTPUT DIGITAL INPUT 0 to +10V ±5V ±10V MSB LSB ↓ ↓ 111111111111 100000000000 011111111111 000000000000 LSB +9.9976V +5V +4.9976V 0V 2.4mV +4.9976V 0V –0.0024V –5V 2.44mV +9.9951V 0V –0.0049V –10V 4.88mV GAIN ADJUSTMENT For either unipolar or bipolar configurations, apply the digital input that should give the maximum positive voltage output. Adjust the gain potentiometer for this positive full scale voltage. See Table III for positive full scale voltages. 10k Ω to 100kΩ 25 VOUT 24 6 ACOM 23 7 Gain Adjust 22 8 –VCC 21 –VCC 9 +VCC 20 +VCC +VCC 3.9MΩ 10 19 11 18 0.0022µF 12 17 1µF 13 16 DCOM 10k Ω to 100kΩ 1µF 15 FIGURE 5. Power Supply, Gain, and Offset Potentiometer Connections. ® DAC811 –VCC 1MΩ 5 14 TABLE III. Digital Input/Analog Output. Connect for Bipolar Operation 6 DAC811 features separate digital and analog power supply returns to permit optimum connections for low noise and high speed performance. The analog common (pin 23) and digital common (pin 15) should be connected together at one point. Separate returns minimize current flow in low level signal paths if properly connected. Logic return currents are not added into the analog signal return path. A ±0.5V difference between ACOM and DCOM is permitted for specified operation. High frequency noise on DCOM with respect to ACOM may permit noise to be coupled through to the analog output; therefore, some caution is required in applying these common connections. From Voltage Reference From D/A Converter 180kΩ 26 Summing Junction 25 10V Range 24 VOUT 23 Analog Common 4.26kΩ OUTPUT RANGE DIGITAL INPUT CODES CONNECT PIN 25 TO CONNECT PIN 27 TO 0 to +10V ±5 ±10V USB BOB or BTC BOB or BTC 24 24 NC 23 26 26 TABLE IV. Output Range Connections. APPLICATIONS MICROCOMPUTER BUS INTERFACING The DAC811 interface logic allows easy interface to microcomputer bus structures. The control signal WR is derived from external device select logic and the I/O Write or Memory Write (depending upon the system design) signals from the microcomputer. The latch enable lines NA, NB, NC and LDAC determine which of the latches are enabled. It is permissible to enable two or more latches simultaneously, as shown in some of the following examples. The double-buffered latch permits data to be loaded into the input latches of several DAC811s and later strobed into the D/A latch of all D/As, simultaneously updating all analog outputs. All the interface schemes shown below use a base address decoder. If blocks of memory are used, the base address decoder can be simplified or eliminated altogether. For instance, if half the memory space is unused, address line A15 of the microcomputer can be used as the chip select control. 100kΩ 12kΩ 3.9MΩ Bipolar Offset FIGURE 7. Output Amplifier Voltage Range Scaling Circuit. EXTERNAL OFFSET AND GAIN ADJUSTMENT Offset and Gain may be trimmed by installing external Offset and Gain potentiometers. Connect these potentiometers as shown in Figure 5. TCR of the potentiometers should be 100ppm/°C or less. The 1MΩ and 3.9MΩ resistors (20% carbon or better) should be located close to the DAC811 to prevent noise pickup. If it is not convenient to use these high value resistors, an equivalent “T” network, as shown in Figure 6, may be substituted in each case. The Gain Adjust (pin 22) is a high impedance point and a 0.001µF to 0.01µF ceramic capacitor should be connected from this pin to Analog Common to reduce noise pickup in all applications, including those not employing external gain adjustment. Excessive capacitance on the Gain Adjust or Offset Adjust pin may affect slew rate and settling time. 100kΩ 27 4.26kΩ The Analog Common is the high quality return for the D/A converter and should be connected directly to the analog reference point of the system. The load driven by the output amplifier should be returned to the Analog Common. 1MΩ 5.36kΩ 180kΩ 10kΩ 4-BIT INTERFACE An interface to a 4-bit microcomputer is shown in Figure 8. Each DAC811 occupies four address locations. A 74LS139 provides the two-to-four decoder and selects it with the base address. Memory Write (WR) of the microcomputer is connected directly to the WR pin of the DAC811. An 8205 decoder is an alternative to the 74LS139. FIGURE 6. Equivalent Resistances. OUTPUT RANGE CONNECTIONS Internal scaling resistors provided in the DAC811 may be connected to produce bipolar output voltage ranges of ±10V and ±5V or a unipolar output voltage range of 0 to +10V. The 20V range (±10V bipolar range) is internally connected. Refer to Figure 7. Connections for the output ranges are listed in Table IV. ® 7 DAC811 8-BIT INTERFACE The control logic of DAC811 permits interfacing to rightjustified data formats, as illustrated in Figure 9. When a 12-bit D/A converter is loaded from an 8-bit bus, two bytes of data are required. Figures 10 and 11 show an addressing scheme for right-justified and left-justified data respectively. The base address is decoded from the high-order address bits. A0 and A1 address the appropriate latches. Note that adjacent addresses are used. For the right-justified case, X1016 loads the 8LSBs, and X0116 loads the 4MSBs and simultaneously transfers input latch data to the D/A latch. Addresses X0016 and X1116 are not used. 16 D0 10 D8 17 D1 DB0 DB1 9 D9 18 D2 DB2 8 D10 19 D3 Left-justified data is handled in a similar manner, shown in Figure 11. The DAC811 still occupies two adjacent locations in the microcomputer's memory map. 7 D11 DB4 14 D4 DB5 13 D5 DB6 12 D6 DB7 11 D7 2 WR 3 LDAC 4 NA 5 NB 6 NC DAC811 Microcomputer DB3 WR A15 DB3 D4 10 D8 17 D1 13 D5 9 D9 18 D2 12 D6 8 D10 19 D3 11 D7 7 D11 2 WR WR AN Base Address Decoder A2 1 Y3 A1 3 A1 Y2 A0 2 A0 Y1 Y0 7 6 5 4 FIGURE 10. Right-Justified Data Bus Interface. X X D11 D10 D9 D8 3 LDAC 12 D6 11 D7 10 D8 16 D0 4 NA 5 NB 6 NC 9 D9 17 D1 DB4 8 D10 DB5 18 D2 DB6 7 D11 DB7 19 D3 2 WR 3 LDAC 4 NA 5 NB 6 NC DB3 WR A2 D7 D6 D5 D4 D3 D2 D1 D0 D3 D2 D1 D0 D5 DB2 A1 a. Right-Justified D11 D10 D9 D8 D7 D6 D5 D4 D4 13 DB1 A15 X 14 DB0 FIGURE 8. Addressing and Control for 4-Bit Microcomputer Interface. X CS A0 CS (Chip Select) EN 1/2 74LS139 A2 A1 Microcomputer Microcomputer DB2 D0 14 X X X X A0 Base Address Decoder CS b. Left-Justified FIGURE 11. Left-Justified Data Bus Interface. FIGURE 9. 12-Bit Data Format for 8-Bit Systems. ® DAC811 DAC811 DB1 16 DAC811 DB0 Base Address Decoder 8 INTERFACING MULTIPLE DAC811s IN 8-BIT SYSTEMS Many applications, such as automatic test systems, require that the outputs of several D/A converters be updated simultaneously. The interface shown in Figure 12 uses a 74LS138 decoder to decode a set of eight adjacent addresses, to load the input latches of four DAC811s. The example shows a right-justified data format. eight address spaces for other uses. Incorporate A3 into the base address decoder, remove the inverter, connect the common LDAC line to NC of D/A #4, and connect D1 of the 74LS138 to +5V. 12- AND 16-BIT MICROCOMPUTER INTERFACE For this application, the input latch enable lines, NA, NB and NC, are tied low, causing the latches to be transparent. The D/A latch, and therefore DAC811, is selected by the address decoder and strobed by WR. A ninth address using A3 causes all DAC811s to be updated simultaneously. If a particular DAC811 is always loaded last—for instance, D/A #4—A3 is not needed, thus saving WR A15 A4 WR Base Address Decoder LDAC CS NC DAC811 (1) NB NA A3 A3 Microcomputer 74LS138 4 5 6 15 G2A G2B G1 Y0 Y1 Y2 14 13 12 A2 A1 A0 3 0 0 0 0 Load 8 LSB – D/A #1 0 0 0 1 Load 4 MSB – D/A #1 LDAC 0 0 1 0 Load 8 MSB – D/A #2 0 0 1 1 Load 4 MSB – D/A #2 NB 0 1 0 0 Load 8 MSB – D/A #3 NA 0 1 0 1 Load 4 MSB – D/A #3 0 1 1 0 Load 8 MSB – D/A #4 0 1 1 1 Load 4 MSB – D/A #4 1 X X X Load D/A Latch—All D/A NC DAC811 (2) 2 1 B Y6 A Y7 WR LDAC Y5 C 9 7 OPERATION WR Y3 11 Y4 10 ADDRESS BUS A2 A1 A0 NC DAC811 (4) NB NA FIGURE 12. Interfacing Multiple DAC811s to an 8-Bit Bus. ® 9 DAC811