® DAC701 DAC702 DAC703 DAC 701 DAC 702 DAC 703 Monolithic 16-Bit DIGITAL-TO-ANALOG CONVERTERS FEATURES ● VOUT AND IOUT MODELS ● HIGH ACCURACY: Linearity Error ±0.0015% of FSR max Differential Linearity Error ±0.003% of FSR max ● MONOTONIC (at 15 bits) OVER FULL SPECIFICATION TEMPERATURE RANGE ● PIN-COMPATIBLE WITH DAC70, DAC71, DAC72 DESCRIPTION Digital inputs are complementary binary coded and are TTL-, LSTTL-, 54/74C- and 54/74HC-compatible over the entire temperature range. Outputs of 0 to +10V, ±10V, 0 to –2mA, and ±1mA are available. The DAC70X family comprise of complete 16-bit digital-to-analog converters that includes a precision buried-zener voltage reference and a low-noise, fastsettling output operational amplifier (voltage output models), all on one small monolithic chip. A combination of current-switch design techniques accomplishes not only 15-bit monotonicity over the entire specified temperature range, but also a maximum end-point linearity error of ±0.0015% of full-scale range. Total full-scale gain drift is limited to ±10ppm/°C maximum (LH and CH grades). Digital Inputs 16-Bit Ladder Resistor Network And Current Switches ● DUAL-IN-LINE PLASTIC AND HERMETIC CERAMIC AND SOIC These D/A converters are packaged in hermetic 24-pin ceramic side-brazed or molded plastic. The DIP-packaged parts are pin-compatible with the voltage and current output DAC71 and DAC72 model families. The DAC702 is also pin-compatible with the DAC70 model family. In addition, the DAC703 is offered in a 24-pin SOIC package for surface mount applications. Reference Circuit Reference Output Common Summing Junction Output Voltage Models Only Gain Adjust +V CC –V CC V DD 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/ • FAXLine: (800) 548-6133 (US/Canada Only) • Cable: BBRCORP • Telex: 066-6491 • FAX: (520) 889-1510 • Immediate Product Info: (800) 548-6132 ® © 1983 Burr-Brown Corporation SBAS143 PDS-494M 1 DAC701, 702, 703 Printed in U.S.A. March, 1998 SPECIFICATIONS At +25°C and rated power supplies, unless otherwise noted. DAC702/703J PARAMETER MIN TYP DAC701/702/703K MAX MIN TYP DAC701/702/703B, S MAX MIN TYP MAX DAC701/702/703L, C MIN TYP MAX UNITS ✻ Bits ✻ ✻ ✻ ✻ V V µA mA INPUT DIGITAL INPUT Resolution Digital Inputs (1) VIH VIL IIH, VI = +2.7V IIL, VI = +0.4V ✻ 16 ✻ ✻ ✻ ✻ ✻ ±0.006 ✻ ±0.003 ±0.012 ±0.07 ±0.05 ±0.30 ±0.10 +2.4 –1.0 –0.35 +VCC +0.8 +40 –0.5 ±0.0015 ✻ ✻ ✻ ✻ ✻ ✻ ✻ ✻ ✻ ✻ ✻ ✻ ±0.003 ✻ ✻ ±0.00075 ±0.0015 ✻ ±0.006 ✻ ✻ ±0.0015 ±0.003 % of FSR ±0.003 ✻ ✻ ±0.006 ±0.15 ✻ ±0.0015 ±0.05 ✻ ±0.003 ±0.10 ✻ ✻ ✻ ✻ ✻ ✻ ✻ % of FSR % % of FSR ✻ TRANSFER CHARACTERISTICS ACCURACY(2) Linearity Error(4) Differential Linearity Error(4) Differential Linearity Error at Bipolar Zero (DAC702/703)(4) Gain Error(5) Zero Error(5, 6) Monotonicity Over Spec. Temp Range 13 DRIFT (over specification temperature range) Total Error Over Temperature Range (all models)(7) Total Full Scale Drift: DAC701 DAC702/703 Gain Drift (all models) Zero Drift: DAC701 DAC702/703 Differential Linearity Over Temp.(4) 15 Bits ±0.08 ✻ ±0.15 ±0.05 ±0.10 ✻ ✻ % of FSR ±10 ±10 ±10 ±30 ✻ ✻ ✻ ±30 ±25 ±25 ±8.5 ±7 ±7 ±18 ±15 ±15 ±6 ✻ ±5 ±13 ✻ ±10 ppm of FSR/°C ppm of FSR/°C ppm/°C ±5 ±15 ±2.5 ✻ ±5 ±12 ±1.5 ±4 ±3 ±10 ✻ ±2.5 ✻ ±5 ppm of FSR/°C ppm of FSR/°C Linearity Error Over Temp.(4) SETTLING TIME (to ±0.003% of FSR)(8) DAC701/703 (VOUT Models) Full Scale Step, 2kΩ Load 1LSB Step at Worst-Case Code(9) Slew Rate DAC702 (IOUT Models) Full Scale Step (2mA), 10 to 100Ω Load 1kΩ Load ✻ 14 % of FSR(3) ±0.012 +0.009, –0.006 ✻ +0.006, –0.003 % of FSR ±0.012 ±0.006 ✻ ±0.003 % of FSR ✻ µs 4 ✻ 2.5 10 ✻ ✻ 350 1 ✻ ✻ ±10 0 to +10 ✻ ✻ 8 ✻ ✻ ✻ ✻ ✻ ✻ 1000 3 µs V/µs ✻ ✻ ✻ ✻ ✻ ✻ ✻ ✻ ns µs OUTPUT VOLTAGE OUTPUT MODELS DAC701 (CSB Code) DAC703 (COB Code) Output Current Output Impedance Short Circuit to Common Duration CURRENT OUTPUT MODELS DAC702 (COB Code)(10) Output Impedance(10) Compliance Voltage ±5 ✻ ✻ ✻ ✻ ✻ ✻ 0.15 ✻ ✻ ✻ Indefinite ✻ ✻ ✻ ±1 2.45 ±2.5 ✻ ✻ ✻ ✻ ✻ ✻ ✻ ✻ ✻ ® DAC701, 702, 703 2 V V mA Ω mA kΩ V SPECIFICATIONS (CONT) At +25°C and rated power supplies, unless otherwise noted. DAC702/703J PARAMETER MIN REFERENCE VOLTAGE Voltage Source Current Available for External Loads Temperature Coefficient Short Circuit to Common Duration TYP DAC701/702/703K MAX DAC701/702/703B, S DAC701/702/703L, C MIN TYP MAX MIN TYP MAX MIN TYP MAX UNITS +6.3 +6.0 +6.3 +6.6 +6.24 +6.3 +6.36 ✻ ✻ ✻ V +2.5 ±10 +1.5 ✻ ✻ ✻ ✻ ✻ ✻ ±25 ±15 ✻ ✻ ✻ mA ppm/°C ✻ ✻ ✻ ✻ ✻ ✻ V V V ✻ Indefinite ✻ ✻ POWER SUPPLY REQUIREMENTS Voltage: +VCC –VCC VDD Current (No Load): DAC702 (IOUT Models) +VCC –VCC VDD DAC701/703 (VOUT Models) +VCC –VCC VDD Power Dissipation: (VDD = +5.0V)(11) DAC702 DAC701/703 Power Supply Rejection: +VCC –VCC VDD 13.5 13.5 +4.5 ✻ ✻ ✻ ✻ ✻ ✻ +25 –25 +8 ✻ ✻ ✻ +30 –30 +8 15 15 +5 16.5 16.5 +16.5 +10 –13 +4 +16 –18 +4 ✻ ✻ ✻ 365 530 ±0.0015 ±0.0015 ±0.0001 ±0.006 ±0.006 ±0.001 ✻ ✻ ✻ ✻ ✻ ✻ ✻ ✻ ✻ ✻ ✻ ✻ ✻ ✻ ✻ ✻ ✻ ✻ ✻ ✻ ✻ ✻ ✻ ✻ ✻ ✻ ✻ mA mA mA ✻ ✻ ✻ ✻ ✻ ✻ ✻ ✻ ✻ ✻ ✻ ✻ ✻ ✻ ✻ ✻ ✻ ✻ mA mA mA ✻ ✻ 790 940 ✻ ✻ 630 780 ✻ ✻ ✻ ✻ mW mW ✻ ✻ ✻ ✻ ✻ ✻ ✻ ✻ ✻ ±0.003 ±0.003 ✻ ✻ ✻ ✻ ✻ ✻ ✻ % of FSR/%VCC % of FSR/%VCC % of FSR/%VDD ✻ ✻ 0 ✻ +70 ✻ °C °C °C °C °C TEMPERATURE RANGE Specification: B, C Grades S Grades J, K, L Grades Storage: Ceramic Plastic, SOIC 0 –60 +70 +100 ✻ –60 ✻ ✻ +150 ✻ –25 –55 +85 +125 ✻ ✻ ✻ Specification same as model to the left. NOTES: (1) Digital inputs are TTL, LSTTL, 54/74C, 54/74HC, and 54/74HTC compatible over the operating voltage range of VDD = +5V to +15V and over the specified temperature range. The input switching threshold remains at the TTL threshold of 1.4V over the supply range of VDD = +5V to +15V. As logic “0” and logic “1” inputs vary over 0V to +0.8V and +2.4V to +10V respectively, the change in the D/A converter output voltage will not exceed ±0.0015% of FSR for the LH and CH grades, ±0.003% of FSR for the BH grade and ±0.006% of FSR for the KG grade. (2) DAC702 (current-output models) is specified and tested with an external output operational amplifier connected using the internal feedback resistor in all parameters except settling time. (3) FSR means full-scale range and is 20V for the ±10V range (DAC703), 10V for the 0 to +10V range (DAC701). FSR is 2mA for the ±1mA range (DAC702). (4) ±0.0015% of full-scale range is equivalent to 1LSB in 15-bit resolution. ±0.003% of full-scale range is equivalent to 1LSB in 14-bit resolution. ±0.006% of full-scale range is equivalent to 1LSB in 13-bit resolution. (5) Adjustable to zero with external trim potentiometer. Adjusting the gain potentiometer rotates the transfer function around the zero point. (6) Error at input code FFFFH for DAC701, 7FFFH for DAC702 and DAC703. (7) With gain and zero errors adjusted to zero at +25°C. (8) Maximum represents the 3σ limit. Not 100% tested for this parameter. (9) At the major carry, 7FFFH to 8000H and 8000H to 7FFFH. (10) Tolerance on output impedance and output current is ±30%. (11) Power dissipation is an additional 40mW when VDD is operated at +15V. 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 DAC701, 702, 703 CONNECTION DIAGRAMS MSB Reference Circuit 1 24 2 (2) +VCC 23 270kΩ 3 (3) 22 0.0022µF 4 21 5 20 3.9MΩ (3) Digital Inputs 6 7 8 9 16-Bit Ladder Resistor Network and Current Switches 10 RF (4) –V CC 19 (2) 18 V DD (1) 17 LSB Voltage Models Only (2) 16 15 11 14 12 13 Digital Inputs NOTES: (1) Can be tied to +VCC instead of having separate VDD supply. (2) Decoupling capacitors are 0.1µF to 1.0µF. (3) Potentiometers are 10kΩ to 100kΩ. (4) 5kΩ (DAC701), 10kΩ (DAC702/703). ABSOLUTE MAXIMUM RATINGS(1) PIN ASSIGNMENTS ALL PACKAGES PIN # DAC702 DAC701/703 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 Bit 1 (MSB) Bit 2 Bit 3 Bit 4 Bit 5 Bit 6 Bit 7 Bit 8 Bit 9 Bit 10 Bit 11 Bit 12 Bit 13 Bit 14 Bit 15 Bit 16 (LSB) RFEEDBACK VDD –VCC Common IOUT Gain Adjust +VCC +6.3V Reference Output Bit 1 (MSB) Bit 2 Bit 3 Bit 4 Bit 5 Bit 6 Bit 7 Bit 8 Bit 9 Bit 10 Bit 11 Bit 12 Bit 13 Bit 14 Bit 15 Bit 16 (LSB) VOUT VDD –VCC Common Summing Junction (Zero Adjust) Gain Adjust +VCC +6.3V Reference Output +VCC to Common ........................................................................ 0V, +18V –VCC to Common ........................................................................ 0V, –18V VDD to Common .......................................................................... 0V, +18V Digital Data Inputs to Common ................................................ –1V, +18V Reference Out to Common ........................... Indefinite Short to Common External Voltage Applied to RF (DAC702) ......................................... ±18V External Voltage Applied to D/A Output (DAC701/703) .......... –5V to +5V VOUT (DAC701/703) ....................................... Indefinite Short to Common Power Dissipation ................................................................................. 1W Storage Temperature ...................................................... –60°C to +150°C Lead Temperature (soldering, 10s) ................................................. 300°C NOTE: (1) Stresses above those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. Exposure to absolute maximum conditions for extended periods may affect device reliability. ELECTROSTATIC DISCHARGE SENSITIVITY 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. ® DAC701, 702, 703 4 PACKAGE/ORDERING INFORMATION TEMPERATURE RANGE LINEARITY ERROR, MAX AT+25°C (% of FSR) GAIN DRIFT, MAX (ppm/°C) PRODUCT PACKAGE PACKAGE DRAWING NUMBER(1) DAC703JP DAC703KP 24-Pin Plastic DIP 24-Pin Plastic DIP 167 167 ±1mA, ±10V ±1mA, ±10V 0°C to +70°C 0°C to +70°C ±0.006 ±0.003 ±30 ±25 DAC701KH DAC702KH DAC703KH 24-Pin Ceramic DIP 24-Pin Ceramic DIP 24-Pin Ceramic DIP 165 165 165 0 to –2mA, 0 to +10V ±1mA, ±10V ±1mA, ±10V 0°C to +70°C 0°C to +70°C 0°C to +70°C ±0.003 ±0.003 ±0.003 ±25 ±25 ±25 DAC701BH DAC702BH DAC703BH 24-Pin Ceramic DIP 24-Pin Ceramic DIP 24-Pin Ceramic DIP 165 165 165 0 to –2mA, 0 to +10V ±1mA, ±10V ±1mA, ±10V –25°C to +85°C –25°C to +85°C –25°C to +85°C ±0.003 ±0.003 ±0.003 ±15 ±15 ±15 DAC701LH DAC702LH DAC703LH 24-Pin Ceramic DIP 24-Pin Ceramic DIP 24-Pin Ceramic DIP 165 165 165 0 to –2mA, 0 to +10V ±1mA, ±10V ±1mA, ±10V 0°C to +70°C 0°C to +70°C 0°C to +70°C ±0.0015 ±0.0015 ±0.0015 ±10 ±10 ±10 DAC701CH DAC702CH DAC703CH 24-Pin Ceramic DIP 24-Pin Ceramic DIP 24-Pin Ceramic DIP 165 165 165 0 to –2mA, 0 to +10V ±1mA, ±10V ±1mA, ±10V –25°C to +85°C –25°C to +85°C –25°C to +85°C ±0.0015 ±0.0015 ±0.0015 ±10 ±10 ±10 DAC701SH DAC702SH DAC703SH 24-Pin Ceramic DIP 24-Pin Ceramic DIP 24-Pin Ceramic DIP 165 165 165 0 to –2mA, 0 to +10V ±1mA, ±10V ±1mA, ±10V –55°C to +125°C –55°C to +125°C –55°C to +125°C ±0.003 ±0.003 ±0.003 ±15 ±15 ±15 DAC703JU DAC703KU 24-Pin SOIC 24-Pin SOIC 239 239 ±10V ±10V 0°C to +70°C 0°C to +70°C ±0.006 ±0.003 ±30 ±25 OUTPUT CONFIGURATION NOTE: (1) For detailed drawing and dimension table, please see end of data sheet, or Appendix C of Burr-Brown IC Data Book. ® 5 DAC701, 702, 703 DISCUSSION OF SPECIFICATIONS Zero Drift Zero drift is a measure of the change in the output with FFFFH (DAC701) applied to the digital inputs over the specified temperature range. For the bipolar models, zero is measured at 7FFFH (bipolar zero) applied to the digital inputs. This code corresponds to zero volts (DAC703) or zero milliamps (DAC702) at the analog output. The maximum change in offset at tMIN or tMAX is referenced to the zero error at +25°C and is divided by the temperature change. This drift is expressed in parts per million of full scale range per degree centigrade (ppm of FSR/°C). DIGITAL INPUT CODES The DAC701/702/703 accept complementary digital input codes in either binary format (CSB, unipolar or COB, bipolar). The COB models DAC702/703 may be connected by the user for either complementary offset binary (COB) or complementary two’s complement (CTC) codes (see Table I). ANALOG OUTPUT DIGITAL INPUT CODES 0000H 7FFFH 8000H FFFFH DAC701 Complementary Straight Binary (CSB) DAC702/703 Complementary Offset Binary (COB) DAC702/703 Complementary Two’s Complement (CTC)* + Full Scale +1/2 Full Scale +1/2 Full Scale –1LSB Zero + Full Scale Bipolar Zero –1LSB –1LSB – Full Scale + Full Scale – Full Scale Bipolar Zero SETTLING TIME Settling time of the D/A is the total time required for the analog output to settle within an error band around its final value after a change in digital input. Refer to Figure 1 for typical values for this family of products. Voltage Output Settling times are specified to ±0.003% of FSR (±1/2LSB for 14 bits) for two input conditions: a full-scale range change of 20V (DAC703) or 10V (DAC701) and a 1LSB change at the “major carry,” the point at which the worstcase settling time occurs. (This is the worst-case point since all of the input bits change when going from one code to the next). * Invert the MSB of the COB code with an external inverter to obtain CTC code. TABLE I. Digital Input Codes. ACCURACY Linearity This specification describes one of the most important measures of performance of a D/A converter. Linearity error is the deviation of the analog output from a straight line drawn through the end points (all bits ON point and all bits OFF point). Current Output Settling times are specified to ±0.003% of FSR for a fullscale range change for two output load conditions: one for 10Ω to 100Ω and one for 1000Ω. It is specified this way because the output RC time constant becomes the dominant factor in determining settling time for large resistive loads. Differential Linearity Error Differential linearity error (DLE) of a D/A converter is the deviation from an ideal 1LSB change in the output from one adjacent output state to the next. A differential linearity error specification of ±1/2LSB means that the output step sizes can be between 1/2LSB and 3/2LSB when the input changes from one adjacent input state to the next. A negative DLE specification of no more than –1LSB (–0.006% for 14-bit resolution) insures monotonicity. Final-Value Error Band, Percent of Full-Scale Range (±% of FSR) 1 Monotonicity Monotonicity assures that the analog output will increase or remain the same for increasing input digital codes. The DAC701/702/703 are specified to be monotonic to 14 bits over the entire specification temperature range. DAC701 DAC703 0.1 0.01 0.001 0.01 RL = 100Ω RL = 1kΩ 0.1 1 10 Settling Time (µs) FIGURE 1. Final-Value Error Band vs Full-Scale Range Settling Time. DRIFT Gain Drift Gain drift is a measure of the change in the full-scale range output over temperature expressed in parts per million per degree centigrade (ppm/°C). Gain drift is established by: (1) testing the end point differences for each D/A at tMIN, +25°C and tMAX; (2) calculating the gain error with respect to the +25°C value; and (3) dividing by the temperature change. COMPLIANCE VOLTAGE Compliance voltage applies only to current output models. It is the maximum voltage swing allowed on the output current pin while still being able to maintain specified accuracy. ® DAC701, 702, 703 DAC702 6 POWER SUPPLY SENSITIVITY Power supply sensitivity is a measure of the effect of a change in a power supply voltage on the D/A converter output. It is defined as a percent of FSR change in the output per percent of change in either the positive supply (+VCC), negative supply (–VCC) or logic supply (VDD) about the nominal power supply voltages (see Figure 2). less. The 3.9MΩ and 270kΩ resistors (±20% carbon or better) should be located close to the D/A converter to prevent noise pickup. If it is not convenient to use these high-value resistors, an equivalent “T” network, as shown in Figure 3, may be substituted in place of the 3.9MΩ part. A 0.001µF to 0.01µF ceramic capacitor should be connected from Gain Adjust to Common to prevent noise pickup. Refer to Figures 4 and 5 for the relationship of zero and gain adjustments to unipolar and bipolar D/A converters. 0.030 ≡ 3.9MΩ 180kΩ 180kΩ 10kΩ 0.025 0.020 FIGURE 3. Equivalent Resistances. 0.015 +15V Supply 0.005 + Full Scale 0 1LSB 1 10 100 1k 10k 100k Power Supply Ripple Frequency (Hz) FIGURE 2. Power Supply Rejection vs Power Supply Ripple Frequency. Range of Zero Adjust REFERENCE SUPPLY All models have an internal low-noise +6.3V reference voltage derived from an on-chip buried zener diode. This reference voltage, available to the user, has a tolerance of ±5% (KH models) and ±1% (BH models). A minimum of 1.5mA is available for external loads. Since the output impedance of the reference output is typically 1W, the external load should remain constant. Gain Adjust Rotates the Line Input = FFFFH Range of Gain Adjust Input = 0000 H Zero Adjust Translates the Line Digital Input FIGURE 4. Relationship of Zero and Gain Adjustments for Unipolar D/A Converters, DAC701. 1LSB If a varying load is to be driven by the reference supply, an external buffer amplifier is recommended to drive the load in order to isolate the bipolar offset (connected internally to the reference) from load variations. Range of Gain Adjust + Full Scale Analog Output OPERATING INSTRUCTIONS POWER SUPPLY CONNECTIONS For optimum performance and noise rejection, power supply decoupling capacitors should be added as shown in the Connection Diagram. 1µF tantalum capacitors should be located close to the D/A converter. EXTERNAL ZERO AND GAIN ADJUSTMENT Zero and gain may be trimmed by installing external zero and gain potentiometers. Connect these potentiometers as shown in the Connection Diagram and adjust as described below. TCR of the potentiometers should be 100ppm/°C or Input = FFFFH Gain Adjust Rotates the Line Full Scale Range +5V Supply Full Scale Range –15V Supply 0.01 Analog Output % of FSR Error Per % of Change in VSUPPLY It is specified for DC or low frequency changes. The typical performance curve in Figure 2 shows the effect of high frequency changes in power supply voltages. Input = 0000 H MSB on All Others Off 7FFF H – Full Scale Offset Adjust Translates the Line Range and Offset Adjust Digital Input FIGURE 5. Relationship of Zero and Gain Adjustments for Bipolar D/A Converters, DAC702 and DAC703. ® 7 DAC701, 702, 703 In many applications it is impractical to sense the output voltage at the output pin. Sensing the output voltage at the system ground point is permissible with the DAC700 family because the D/A converter is designed to have a constant return current of approximately 2mA flowing from Common. The variation in this current is under 20µA (with changing input codes), therefore R4 can be as large as 3Ω without adversely affecting the linearity of the D/A converter. The voltage drop across R4 (R4 x 2mA) appears as a zero error and can be removed with the zero calibration adjustment. This alternate sensing point (the system ground point) is shown in Figures 6, 7, and 8. Zero Adjustment For unipolar (CSB) configurations, apply the digital input code that produces zero voltage or zero current output and adjust the zero potentiometer for zero output. For bipolar (COB, CTC) configurations, apply the digital input code that produces zero output voltage or current. See Table II for corresponding codes and the Connection Diagram for zero adjustment circuit connections. Zero calibration should be made before gain calibration. Gain Adjustment Apply the digital input that gives the maximum positive output voltage. Adjust the gain potentiometer for this positive full scale voltage. See Table II for positive full scale voltages and the Connection Diagram for gain adjustment circuit connections. Figures 7 and 8 show two methods of connecting the current output models (DAC702) with external precision output op amps. By sensing the output voltage at the load resistor (ie, by connecting RF to the output of A1 at RL), the effect of R1 and R2 is greatly reduced. R1 will cause a gain error but is independent of the value of RL and can be eliminated by initial calibration adjustments. The effect of R2 is negligible because it is inside the feedback loop of the output op amp and is therefore greatly reduced by the loop gain. INSTALLATION CONSIDERATIONS This D/A converter family is laser-trimmed to 14-bit linearity. The design of the device makes the 16-bit resolution available. If 16-bit resolution is not required, bit 15 and bit 16 should be connected to VDD through a single 1kΩ resistor. DAC701 Due to the extremely high resolution and linearity of the D/A converter, system design problems such as grounding and contact resistance become very important. For a 16-bit converter with a 10V full-scale range, 1LSB is 153µV. With a load current of 5mA, series wiring and connector resistance of only 30mΩ will cause the output to be in error by 1LSB. To understand what this means in terms of a system layout, the resistance of #23 wire is about 0.021Ω/ft. Neglecting contact resistance, less than 18 inches of wire will produce a 1LSB error in the analog output voltage! RF RDAC A1 4kΩ VOUT R2 RB * RL R3 Common Alternate Ground Sense Connection R4 Sense Output +V To +VCC 1µF In Figures 6, 7, and 8, lead and contact resistances are represented by R1 through R5. As long as the load resistance RL is constant, R2 simply introduces a gain error and can be removed during initial calibration. R3 is part of RL, if the output voltage is sensed at Common, and therefore introduces no error. If RL is variable, then R2 should be less than RL MIN/216 to reduce voltage drops due to wiring to less than 1LSB. For example, if RL MIN is 5kΩ, then R2 should be less than 0.08Ω. RL should be located as close as possible to the D/A converter for optimum performance. The effect of R4 is negligible. COM 1µF To –VCC ±15VDC Supply –V System Ground Point +V To VDD 1µF COM +5VDC Supply * RB = 2kΩ (DAC701 and DAC703) FIGURE 6. Output Circuit for Voltage Models. ® DAC701, 702, 703 5kΩ 8 VOLTAGE OUTPUT MODELS ANALOG OUTPUT DAC701 UNIPOLAR DIGITAL INPUT CODE 1LSB 0000H FFFFH (µV) (V) (V) DAC703 BIPOLAR 16-BIT 15-BIT 14-BIT 16-BIT 15-BIT 14-BIT 153 +9.99985 0 305 +9.99969 0 610 +9.99939 0 305 +9.99960 –10.0000 610 +9.99939 –10.0000 1224 +9.99878 –10.0000 ANALOG OUTPUT MODEL ANALOG OUTPUT DAC702 BIPOLAR DIGITAL INPUT CODE 1LSB 0000H FFFFH (µA) (mA) (mA) 16-BIT 15-BIT 14-BIT 0.031 –0.99997 +1.00000 0.061 –0.99994 +1.00000 0.122 –0.99988 +1.00000 TABLE II. Digital Input and Analog Output Relationships. If the output cannot be sensed at Common or the system ground point as mentioned above, the differential output circuit shown in Figure 8 is recommended. In this circuit the output voltage is sensed at the load common and not at the D/A converter common as in the previous circuits. The value of R6 and R7 must be adjusted for maximum common-mode rejection at RL. Note that if R3 is negligible, the circuit of Figure 8 can be reduced to the one shown in Figure 7. Again the effect of R4 is negligible. DAC702 The D/A converter and the wiring to its connectors should be located to provide optimum isolation from sources of RFI and EMI. The key concept in elimination of RF radiation or pickup is loop area; therefore, signal leads and their return conductors should be kept close together. This reduces the external magnetic field along with any radiation. Also, if a single lead and its return conductor are wired close together, they present a small flux-capture cross section for any external field. This reduces radiation pickup in the circuit. R1 RF DAC702 RF * I OUT A1 RDAC * Common RF * RB ‡ R1 RF R2 RL I OUT RDAC * R3 R2 A1 RL Common R7 Alternate Ground Sense Connection R6 R4 Sense Output +V To +VCC 1µF COM 1µF –V To –VCC 1µF COM R3 Alternate Ground Sense Connection ±15VDC Supply R4 +V To +VCC 1µF System Ground Point +V To VDD COM 1µF +5VDC Supply DAC702 RB RF RDAC 2.45kΩ 10k Ω 2.45kΩ System Ground Point +V To VDD DAC702 ‡ R should be equal to the output impedance at the current output B to compensate for the bias current drift of A1. Use standard 10%, 1/4W carbon composition or equivalent resistors. FIGURE 7. Preferred External Op Amp Configuration. ±15VDC Supply –V To –VCC 1µF * R5 Sense Output COM RF RDAC 10k Ω 2.45kΩ +5VDC Supply R5 + R7 = RF + R1 R6 = RDAC FIGURE 8. Differential Sensing Output Op Amp Configuration. ® 9 DAC701, 702, 703 APPLICATIONS RF DRIVING AN EXTERNAL OP AMP WITH CURRENT OUTPUT D/AS 5k Ω DAC702 is current output devices and will drive the summing junction of an op amp to produce an output voltage as shown in Figure 9. Use of the internal feedback resistor is required to obtain specified gain accuracy and low gain drift. I OUT 0 to 2mA 4k Ω VOUT Common DAC702 can be scaled for any desired voltage range with an external feedback resistor, but at the expense of increased drifts of up to ±50ppm/°C. The resistors in the DAC702 ratio track to ±1ppm/°C but their absolute TCR may be as high as ±50ppm/°C. FIGURE 9. External Op Amp Using Internal Feedback Resistors. An alternative method of scaling the output voltage of the D/A converter and preserving the low gain drift is shown in Figure 10. RF 5k Ω 0 to 2mA OUTPUTS LARGER THAN 20V RANGE For output voltage ranges larger than ±10V, a high voltage op amp may be employed with an external feedback resistor. Use IOUT values of ±1mA for bipolar voltage ranges and –2mA for unipolar voltage ranges (see Figure 11). Use protection diodes as shown when a high voltage op amp is used. I OUT 4k Ω R1 * VOUT I R2 * Common * R1 , R2 TCR < ±10ppm/°C FIGURE 10. External Op Amp Using Internal and External Feedback Resistors to Maintain Low Gain Drift. RF RF 0 to 2mA BB3584 4k Ω VOUT FIGURE 11. External Op Amp Using External Feedback Resistors. ® DAC701, 702, 703 10 IMPORTANT NOTICE Texas Instruments and its subsidiaries (TI) reserve the right to make changes to their products or to discontinue any product or service without notice, and advise customers to obtain the latest version of relevant information to verify, before placing orders, that information being relied on is current and complete. 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