DAC7541A ® Low Cost 12-Bit CMOS Four-Quadrant Multiplying DIGITAL-TO-ANALOG CONVERTER FEATURES DESCRIPTION ● FULL FOUR-QUADRANT MULTIPLICATION ● 12-BIT END-POINT LINEARITY ● DIFFERENTIAL LINEARITY ±1/2LSB MAX OVER TEMPERATURE ● MONOTONICITY GUARANTEED OVER TEMPERATURE ● TTL-/CMOS-COMPATIBLE The Burr-Brown DAC7541A is a low cost 12-bit, four-quadrant multiplying digital-to-analog converter. Laser-trimmed thin-film resistors on a monolithic CMOS circuit provide true 12-bit integral and differential linearity over the full specified temperature range. DAC7541A is a direct, improved pin-for-pin replacement for 7521, 7541, and 7541A industry standard parts. In addition to a standard 18-pin plastic package, the DAC7541A is also available in a surface-mount plastic 18-pin SOIC. ● SINGLE +5V TO +15V SUPPLY ● LATCH-UP RESISTANT ● 7521/7541/7541A REPLACEMENT ● PACKAGES: Plastic DIP, Plastic SOIC ● LOW COST 10kΩ VREF 20kΩ 10kΩ 20kΩ 10kΩ 10kΩ 20kΩ 20kΩ 20kΩ 20kΩ SPDT NMOS Switches IOUT 2 IOUT 1 10kΩ Bit 1 (MSB) Bit 2 Bit 3 Bit 11 Digital Inputs (DTL-/TTL-/CMOS-compatible) Logic: A switch is closed to IOUT 1 for its digital input in a “HIGH” state. International Airport Industrial Park • Mailing Address: PO Box 11400 Tel: (520) 746-1111 • Twx: 910-952-1111 • Cable: BBRCORP • © 1987 Burr-Brown Corporation Bit 12 (LSB) RFB Switches shown for digital inputs “HIGH”. • Tucson, AZ 85734 • Street Address: 6730 S. Tucson Blvd. • Tucson, AZ 85706 Telex: 066-6491 • FAX: (520) 889-1510 • Immediate Product Info: (800) 548-6132 PDS-639C Printed in U.S.A. September, 1993 SPECIFICATIONS ELECTRICAL At +25°C, +VDD = +12V or +15V, VREF = +10V, VPIN 1 = V PIN 2 = 0V, unless otherwise specified. DAC7541A PARAMETER ACCURACY Resolution Relative Accuracy Differential Non-linearity Gain Error Gain Temperature Coefficient (∆Gain/∆Temperature) Output Leakage Current: Out1 (Pin 1) Out2 (Pin 2) REFERENCE INPUT Voltage (Pin 17 to GND) Input Resistance (Pin 17 to GND) GRADE TA = +25°C TA = TMAX, TMIN(1) UNITS All J K J K J K 12 ±1 ±1/2 ±1 ±1/2 ±6 ±1 12 ±1 ±1/2 ±1 ±1/2 ±8 ±3 Bits LSB max LSB max LSB max LSB max LSB max LSB max ALL J, K J, K ±5 ±5 5 ±10 ±10 ppm/°C max nA max nA max All All –10/+10 7-18 –10/+10 7-18 V min/max kΩ min/max TEST CONDITIONS/COMMENTS ±1LSB = ±0.024% of FSR. ±1/2LSB = ±0.012% of FSR. All grades guaranteed monotonic to 12 bits, TMIN to TMAX. Measured using internal RFB and includes effect of leakage current and gain T.C. Gain error can be trimmed to zero. Typical value is 2ppm/°C. All digital inputs = 0V. All digital inputs = VDD. Typical input resistance = 11kΩ. Typical input resistance temperature coefficient is –50ppm/°C. DIGITAL INPUTS VIN (Input HIGH Voltage) VIL (Input LOW Voltage) IIN (Input Current) All All All 2.4 0.8 ±1 2.4 0.8 ±1 V min V max µA max Capacitance)(2) CIN (Input All 8 8 pF max POWER SUPPLY REJECTION ∆Gain/∆VDD All ±0.01 ±0.02 % per % max POWER SUPPLY VDD Range All +5 to +16 +5 to +16 All All 2 100 2 500 V min to V max mA max µA max IDD Logic inputs are MOS gates. IIN typ (25°C) = 1nA VIN = 0V VDD = +11.4V to +16V Accuracy is not guaranteed over this range. All digital inputs VIL or VIN. All digital inputs 0V or VDD. NOTES: (1) Temperature ranges are: = 0°C to + 70°C for JP, KP, JU and KU versions. (2) Guaranteed by design but not production tested. AC PERFORMANCE CHARACTERISTICS These characteristics are included for design guidance only and are not production tested. VDD = +15V, VREF = +10V except where stated, VPIN 1 = VPIN 2 = 0V, output amp is OPA606 except where stated. DAC7541A GRADE TA = +25°C TA = TMAX, TMIN(1) UNITS TEST CONDITIONS/COMMENTS PROPAGATION DELAY (from Digital Input change to 90% of final Analog Output) All 100 — ns typ Out1 Load = 100Ω, CEXT = 13pF. Digital Inputs = 0V to VDD or VDD to 0V. DIGITAL-TO-ANALOG GLITCH IMPULSE All 1000 — nV-s typ MULTIPLYING FEEDTHROUGH ERROR (VREF to Out1) All 1.0 — mVp-p max All 0.6 — µs typ All 1.0 — µs max To 0.01% of Full Scale Range. Out1 Load = 100Ω, CEXT = 13pF. Digital Inputs: 0V to VDD or VDD to 0V. All All All All 100 60 70 100 100 60 70 100 pF max pF max pF max pF max Digital Inputs = VIH Digital Inputs = VIH Digital Inputs = VIL Digital Inputs = VIL PARAMETER VREF = 0V, all digital inputs 0V to VDD or VDD to 0V. Measured using OPA606 as output amplifier. VREF = ±10V, 10kHz sine wave. OUTPUT CURRENT SETTLING TIME OUTPUT CAPACITANCE COUT 1 (Pin 1) COUT 2 (Pin 2) COUT 1 (Pin 1) COUT 2 (Pin 2) NOTE: (1) Temperature ranges are: = 0°C to + 70°C for JP, KP, JU and KU versions. ® DAC7541A 2 ABSOLUTE MAXIMUM RATINGS(1) PIN CONNECTIONS VDD (Pin 16) to Ground ...................................................................... +17V VREF (Pin 17) to Ground ..................................................................... +25V VRPB (Pin 18) to Ground ..................................................................... ±25V Digital Input Voltage (pins 4-15) to Ground ............................... –0.4V, VDD VPIN 1, VPIN 2 to Ground ............................................................. –0.4V, VDD Power Dissipation (any Package): To +75°C ..................................................................................... 450mW Derates above +75°C .............................................................. –6mW/°C Lead Temperature (soldering, 10s) ................................................ +300°C Storage Temperature: Plastic Package ......................................... +125°C Top View DIP/SOIC IOUT 1 1 18 RFB IOUT 2 2 17 VREF GND 3 16 +VDD Bit 1 (MSB) 4 15 Bit 12 (LSB) DAC7541A NOTE: (1) Stresses above those listed above may cause permanent damage to the device. This is a stress rating only and functional operation of the device at these or any other condition above those indicated in the operational sections of this specification is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability. ELECTROSTATIC DISCHARGE SENSITIVITY Bit 2 5 14 Bit 11 Bit 3 6 13 Bit 10 Bit 4 7 12 Bit 9 Bit 5 8 11 Bit 8 Bit 6 9 10 Bit 7 PACKAGE INFORMATION The DAC7541A is an ESD (electrostatic discharge) sensitive device. The digital control inputs have a special FET structure, which turns on when the input exceeds the supply by 18V, to minimize ESD damage. However, permanent damage may occur on unconnected devices subject to high energy electrostatic fields. When not in use, devices must be stored in conductive foam or shunts. The protective foam should be discharged to the destination socket before devices are removed. MODEL PACKAGE PACKAGE DRAWING NUMBER(1) DAC7541JP DAC7541KP Plastic DIP Plastic DIP 218 218 DAC7541JU DAC7541KU Plastic SOIC Plastic SOIC 219 219 Plastic DIP Plastic DIP 218 218 DAC7541JP-BI DAC7541KP-BI NOTE: (1) For detailed drawing and dimension table, please see end of data sheet, or Appendix D of Burr-Brown IC Data Book. BURN-IN SCREENING Burn-in screening is an option available for the models in the Ordering Information table. Burn-in duration is 160 hours at the indicated temperature (or equivalent combination of time and temperature). All units are tested after burn-in to ensure that grade specifications are met. To order burn-in, add “-BI” to the base model number. ORDERING INFORMATION MODEL DAC7541AJP DAC7541AKP DAC7541AJU DAC7541AKU PACKAGE TEMPERATURE RANGE RELATIVE ACCURACY (LSB) Plastic DIP Plastic DIP Plastic SOIC Plastic SOIC 0°C to +70°C 0°C to +70°C 0°C to +70°C 0°C to +70°C ±1 ±1/2 ±1 ±1/2 GAIN ERROR (LSB) ±6 ±1 ±6 ±1 BURN-IN SCREENING OPTION See text for details. MODEL PACKAGE TEMPERATURE RANGE RELATIVE ACCURACY (LSB) BURN-IN TEMP. (160 Hours)(1) DAC7541AJP-BI DAC7541AKP-BI Plastic DIP Plastic DIP 0°C to +70°C 0°C to +70°C ±1 ±1/2 +85°C +85°C 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 DAC7541A PAD FUNCTION PAD FUNCTION 1 2 3 4 5 6 7 8 9 IOUT1 IOUT2 GND Bit 1 (MSB) Bit 2 Bit 3 Bit 4 Bit 5 Bit 6 10 11 12 13 14 15 16 17 18 Bit 7 Bit 8 Bit 9 Bit 10 Bit 11 Bit 12 (LSB) +VDD VREF RFEEDBACK Substrate Bias: Isolated. NC: No Connection. MECHANICAL INFORMATION Die Size Die Thickness Min. Pad Size MILS (0.001") MILLIMETERS 104 x 105 ±5 20 ±3 4x4 2.64 x 2.67 ±0.13 0.51 ±0.08 0.10 x 0.10 Metalization Aluminum DIE TOPOLOGY DAC7541A TYPICAL PERFORMANCE CURVES TA = +25°C, V DD = +15V, unless otherwise noted. GAIN ERROR vs SUPPLY VOLTAGE FEEDTHROUGH ERROR vs FREQUENCY 3 10 Feedthrough (% FSR) Gain Error (LSB) 5/2 2 3/2 1 1 0.10 0.010 1/2 0 0.001 5 0 10 15 100 1k 10k Supply Voltage (V) 5/4 5/4 Supply Current (µA) Linearity Error (LSB) 3/2 1 3/4 1/2 1 3/4 VIH = +2.4V 1/2 1/4 1/4 0 0 5 10 15 VIH = VDD 0 Supply Voltage (V) 5 10 Supply Voltage (V) ® DAC7541A 1M SUPPLY CURRENT vs SUPPLY VOLTAGE LINEARITY vs SUPPLY VOLTAGE 3/2 0 100k Frequency (Hz) 4 15 DISCUSSION OF SPECIFICATIONS CIRCUIT DESCRIPTION The DAC7541A is a 12-bit multiplying D/A converter consisting of a highly stable thin-film R-2R ladder network and 12 pairs of current steering switches on a monolithic chip. Most applications require the addition of a voltage or current reference and an output operational amplifier. A simplified circuit of the DAC7541A is shown in Figure 1. The R-2R inverted ladder binarily divides the input currents that are switched between IOUT 1 and IOUT 2 bus lines. This switching allows a constant current to be maintained in each ladder leg independent of the input code. RELATIVE ACCURACY This term (also known as linearity) describes the transfer function of analog output to digital input code. The linearity error describes the deviation from a straight line between zero and full scale. DIFFERENTIAL NONLINEARITY Differential nonlinearity is the deviation from an ideal 1LSB change in the output, from one adjacent output state to the next. A differential nonlinearity specification of ±1.0LSB guarantees monotonicity. The input resistance at VREF (Figure 1) is always equal to RLDR (RLDR is the R/2R ladder characteristic resistance and is equal to value “R”). Since RIN at the VREF pin is constant, the reference terminal can be driven by a reference voltage or a reference current, AC or DC, of positive or negative polarity. GAIN ERROR Gain error is the difference in measure of full-scale output versus the ideal DAC output. The ideal output for the DAC7541A is –(4095/4096) X (VREF). Gain error may be adjusted to zero using external trims. 10kΩ VREF OUTPUT LEAKAGE CURRENT The measure of current which appears at Out1 with the DAC loaded with all zeros, or at Out2 with the DAC loaded with all ones. 20kΩ S1 10kΩ 20kΩ S2 10kΩ 20kΩ 20kΩ S3 20kΩ S12 IOUT 2 MULTIPLYING FEEDTHROUGH ERROR This is the AC error output due to capacitive feedthrough from VREF to Out1 with the DAC loaded with all zeros. This test is performed at 10kHz. IOUT 1 RFB Bit 1 (MSB) Bit 2 Bit 3 Bit 12 (LSB) Digital Inputs (DTL-/TTL-/CMOS-compatible) Switches shown for digital inputs “HIGH”. OUTPUT CURRENT SETTLING TIME This is the time required for the output to settle to a tolerance of ±0.5LSB of final value from a change in code of all zeros to all ones, or all ones to all zeros. FIGURE 1. Simplified DAC Circuit. EQUIVALENT CIRCUIT ANALYSIS Figures 2 and 3 show the equivalent circuits for all digital inputs low and high, respectively. The reference current is switched to IOUT 2 when all inputs are low and IOUT 1 when inputs are high. The IL current source is the combination of surface and junction leakages to the substrate; the 1/4096 current source represents the constant one-bit current drain through the ladder terminal. PROPAGATION DELAY This is the measure of the delay of the internal circuitry and is measured as the time from a digital code change to the point at which the output reaches 90% of final value. DIGITAL-TO-ANALOG GLITCH IMPULSE This is the measure of the area of the glitch energy measured in nV-seconds. Key contributions to glitch energy are digital word-bit timing differences, internal circuitry timing differences, and charge injected from digital logic. DYNAMIC PERFORMANCE Output Impedance The output resistance, as in the case of the output capacitance, is also modulated by the digital input code. The resistance looking back into the IOUT 1 terminal may be anywhere between 10kΩ (the feedback resistor alone when all digital inputs are low) and 7.5kΩ (the feedback resistor in parallel with approximately 30kΩ of the R-2R ladder network resistance when any single bit logic is high). The static accuracy and dynamic performance will be affected by this modulation. The gain and phase stability of the output MONOTONICITY Monotonicity assures that the analog output will increase or stay the same for increasing digital input codes. The DAC7541A is guaranteed monotonic to 12 bits. POWER SUPPLY REJECTION Power supply rejection is the measure of the sensitivity of the output (full scale) to a change in the power supply voltage. ® 5 DAC7541A RFB RFB R = 10kΩ IREF IOUT 1 IL IREF R = 10kΩ R ≈ 10kΩ IOUT 1 VREF 1/4096 60pF IL 90pF R ≈ 10kΩ IOUT 2 IOUT 2 VREF 1/4096 IL IL 90pF FIGURE 2. DAC7541A Equivalent Circuit (All inputs LOW). FIGURE 3. DAC7541A Equivalent Circuit (All inputs HIGH). amplifier, board layout, and power supply decoupling will all affect the dynamic performance of the DAC7541A. The use of a compensation capacitor may be required when highspeed operational amplifiers are used. It may be connected across the amplifier’s feedback resistor to provide the necessary phase compensation to critically dampen the output. See Figures 4 and 6. BINARY INPUT ANALOG OUTPUT MSB LSB 1111 1111 1111 1000 0000 0000 0000 0000 0001 0000 0000 0000 –VREF (4095/4096) –VREF (2048/4096) –VREF (1/4096) 0V TABLE I. Unipolar Codes. C1 phase compensation (10 to 25pF) in Figure 4 may be required for stability when using high speed amplifiers. C1 is used to cancel the pole formed by the DAC internal feedback resistance and output capacitance at Out1. R1 in Figure 5 provides full scale trim capability—load the DAC register to 1111 1111 1111, adjust R1 for VOUT = – VREF (4095/4096). Alternatively, full scale can be adjusted by omitting R1 and R2 and trimming the reference voltage magnitude. APPLICATIONS OP AMP CONSIDERATIONS The input bias current of the op amp flows through the feedback resistor, creating an error voltage at the output of the op amp. This will show up as an offset through all codes of the transfer characteristics. A low bias current op amp such as the OPA606 is recommended. Low offset voltage and VOS drift are also important. The output impedance of the DAC is modulated with the digital code. This impedance change (approximately 10kΩ to 30kΩ) is a change in closed-loop gain to the op amp. The result is that VOS will be multiplied by a factor of one to two depending on the code. This shows up as a linearity error. Offset can be adjusted out using Figure 4. Gain may be adjusted using Figure 5. BIPOLAR FOUR-QUADRANT OPERATION Figure 6 shows the connections for bipolar four-quadrant operation. Offset can be adjusted with the A1 to A2 summing resistor, with the input code set to 1000 0000 0000. Gain may be adjusted by varying the feedback resistor of A2. The input/output relationship is shown in Table II. UNIPOLAR BINARY OPERATION (Two-Quadrant Multiplication) Figure 4 shows the analog circuit connections required for unipolar binary (two-quadrant multiplication) operation. With a DC reference voltage or current (positive or negative polarity) applied at pin 17, the circuit is a unipolar D/A converter. With an AC reference voltage or current, the circuit provides two-quadrant multiplication (digitally controlled attenuation). The input/output relationship is shown in Table I. BINARY INPUT ANALOG OUTPUT MSB LSB 1111 1111 1111 1000 0000 0000 0111 1111 1111 0000 0000 0000 +VREF (2047/2048) 0V –VREF (1/2048) –VREF (2048/2048) TABLE II. Bipolar Codes. ® DAC7541A 55pF 6 MSB B1 • • • • • • • • • • B12 VOUT = –VREF 16 17 4 5 6 7 8 9 10 11 12 13 14 15 C1 RF 18 1 +15V DAC7541A Out1 Out2 VREF B1 2 + B2 4 + B3 8 +•••+ B12 4096 ) –10V ≤ VREF ≤ +10V VOUT OPA604 2 ( 3 0 ≤ VOUT ≤ – 4095 V 4096 REF Where: BN = 1 if the BN digital input is HIGH. BN = 0 if the BN digital input is LOW. 10kΩ Single-Point Ground +VCC FIGURE 4. Basic Connection With Op Amp VOS Adjust: Unipolar (two-quadrant) Multiplying Configuration. MSB B1 • 4 16 • 5 • 6 • 7 • 8 • 9 • • • R1 200Ω • B12 18 1 +15V DAC7541A 17 R2 200kΩ 10 11 12 13 14 15 OPA604 VREF 2 3 10kΩ +VCC FIGURE 5. Basic Connection With Gain Adjust (allows adjustment up or down). 47Ω +VDD 16 18 1 VREF 17 20kΩ 10kΩ A1 DAC7541A 4...15 20kΩ OPA604 or 1/2 OPA2604 C1 33pF VOUT A2 2 3 5kΩ OPA604 or 1/2 OPA2604 Bits 1-12 VOUT = +VREF ( B1 1 + B2 2 + B3 4 +•••+ B12 2048 ) –1 FIGURE 6. Bipolar Four-Quadrant Multiplier. ® 7 DAC7541A DIGITALLY CONTROLLED GAIN BLOCK The DAC7541A may be used in a digitally controlled gain block as shown in Figure 7. This circuit gives a range of gain from one (all bits = one) to 4096 (LSB = one). The transfer function is: –VIN VOUT = B1 B2 B3 B12 + + +•••+ 2 4 8 4096 ( Bits 1 to 12 VIN 18 16 VDD DAC7541A ) 1 17 2 All bits off is an illegal state, as division by zero is impossible (no op amp feedback). Also, errors increase as gain increases, and errors are minimized at major carries (only one bit on at a time). 3 VOUT OPA604 FIGURE 7. Digitally Programmable Gain Block. ® DAC7541A 8