DAC ® 761 DAC DAC7611 1 761 1 12-Bit Serial Input DIGITAL-TO-ANALOG CONVERTER FEATURES DESCRIPTION ● LOW POWER: 2.5mW ● FAST SETTLING: 7µs to 1 LSB ● 1mV LSB WITH 4.095V FULL-SCALE RANGE ● COMPLETE WITH REFERENCE The DAC7611 is a 12-bit digital-to-analog converter (DAC) with guaranteed 12-bit monotonicity performance over the industrial temperature range. It requires a single +5V supply and contains an input shift register, latch, 2.435V reference, DAC, and high speed rail-to-rail output amplifier. For a full-scale step, the output will settle to 1 LSB within 7µs. The device consumes 2.5mW (0.5mA at 5V). ● 12-BIT LINEARITY AND MONOTONICITY OVER INDUSTRIAL TEMP RANGE The synchronous serial interface is compatible with a wide variety of DSPs and microcontrollers. Clock (CLK), serial data in (SDI), and load strobe (LD) comprise the serial interface. In addition, two control pins provide a chip select (CS) function and an asynchronous clear (CLR) input. The CLR input can be used to ensure that the DAC7611 output is 0V on power-up or as required by the application. ● ASYNCHRONOUS RESET TO 0V ● 3-WIRE INTERFACE: Up to 20MHz Clock ● ALTERNATE SOURCE TO DAC8512 APPLICATIONS ● PROCESS CONTROL ● DATA ACQUISITION SYSTEMS The DAC7611 is available in an 8-lead SOIC or 8-pin plastic DIP package and is fully specified over the industrial temperature range of –40°C to +85°C. ● CLOSED-LOOP SERVO-CONTROL ● PC PERIPHERALS ● PORTABLE INSTRUMENTATION VDD DAC7611 Ref 12-Bit DAC VOUT 12 CLR DAC Register LD CS CLK 12 Serial Shift Register SDI GND 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 ® © 1997 Burr-Brown Corporation PDS-1402A 1 Printed in U.S.A. April, 1998 DAC7611 SPECIFICATIONS ELECTRICAL At TA = –40°C to +85°C, and VDD = +5V, unless otherwise noted. DAC7611P, U PARAMETER ACCURACY Resolution Relative Accuracy(1) Differential Nonlinearity Zero-Scale Error Full Scale Voltage ANALOG OUTPUT Output Current Load Regulation Capacitive Load Short Circuit Current Short Circuit Duration DAC7611PB, UB CONDITIONS MIN TYP MAX MIN TYP MAX UNITS Guaranteed Monotonic Code 000H Code FFFH 12 –2 –1 –1 4.079 ±1/2 ±1/2 +1 4.095 +2 +1 +3 4.111 ✻ –1 –1 ✻ 4.087 ±1/4 ±1/4 ✻ 4.095 +1 +1 ✻ 4.103 Bits LSB LSB LSB V Code 800H RLOAD ≥ 402Ω, Code 800H No Oscillation ±5 GND or VDD DIGITAL INPUT Data Format Data Coding Logic Family Logic Levels VIH VIL IIH IIL ±7 1 500 ±70 Indefinite ✻ 3 ✻ ✻ ✻ ✻ ✻ ✻ 2.4 ✻ ✻ ✻ 0.8 ±10 ±10 POWER SUPPLY VDD IDD Power Dissipation Power Supply Sensitivity To ±1 LSB of Final Value +4.75 TEMPERATURE RANGE Specified Performance –40 +5.0 0.5 2.5 0.001 +5.25 1 5 0.004 ✻ +85 ✻ ✻ ✻ ✻ ✻ V V µA µA µs nV-s nV-s ✻ ✻ ✻ 7 15 2 VIH = 5V, VIL = 0V, No Load, at Code 000H VIH = 5V, VIL = 0V, No Load ∆VDD = ±5% mA LSB pF mA ✻ ✻ ✻ Serial Straight Binary TTL DYNAMIC PERFORMANCE Settling Time(2) (tS) DAC Glitch Digital Feedthrough ✻ ✻ ✻ ✻ ✻ V mA mW %/% ✻ °C ✻ Same specification as for DAC7611P, U. NOTES: (1) This term is sometimes referred to as Linearity Error or Integral Nonlinearity (INL). (2) Specification does not apply to negative-going transitions where the final output voltage will be within 3 LSBs of ground. In this region, settling time may be double the value indicated. 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. ® DAC7611 2 PIN CONFIGURATION PIN DESCRIPTION Top View DIP VDD 1 CS 2 CLK 3 SDI 4 8 DAC7611 VOUT 7 GND 6 CLR 5 LD PIN LABEL DESCRIPTION 1 VDD Power Supply 2 CS Chip Select (active LOW). 3 CLK Synchronous Clock for the Serial Data Input. 4 SDI Serial Data Input. Data is clocked into the internal serial register on the rising edge of CLK. 5 LD Loads the Internal DAC Register. NOTE: The DAC register is a transparent latch and is transparent when LD is LOW (regardless of the state of CS or CLK). 6 CLR Asynchronous Input to Clear the DAC Register. When CLR is strobbed LOW, the DAC register is set to 000H and the output voltage to 0V. 7 GND Ground 8 VOUT Voltage Output. Fixed output voltage range of approximately 0V to 4.095V (1mV/LSB). The internal reference maintains this output range over time, temperature, and power supply variations (within the values defined in the specifications section). PIN CONFIGURATION Top View SOIC VDD 1 CS 2 CLK 3 SDI 4 DAC7611 8 VOUT 7 GND 6 CLR 5 LD 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. ABSOLUTE MAXIMUM RATINGS(1) VDD to GND .......................................................................... –0.3V to 6V Digital Inputs to GND ............................................. –0.3V to VDD + 0.3V VOUT to GND ........................................................... –0.3V to VDD + 0.3V Power Dissipation ........................................................................ 325mW Thermal Resistance, θJA ............................................................ 150°C/W Maximum Junction Temperature ................................................. +150°C Operating Temperature Range ...................................... –40°C to +85°C Storage Temperature Range ........................................ –65°C to +150°C Lead Temperature (soldering, 10s) ............................................. +300°C 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. 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. PACKAGE/ORDERING INFORMATION PRODUCT MINIMUM RELATIVE ACCURACY (LSB) DIFFERENTIAL NONLINEARITY (LSB) SPECIFICATION TEMPERATURE RANGE PACKAGE PACKAGE DRAWING NUMBER(1) DAC7611P DAC7611U ±2 ±2 ±1 ±1 –40°C to +85°C –40°C to +85°C 8-Pin DIP 8-Lead SOIC 006 182 ±1 ±1 ±1 ±1 " " " DAC7611PB DAC7611UB " " " –40°C to +85°C –40°C to +85°C 8-Pin DIP 8-Lead SOIC 006 182 " " " " " " ORDERING NUMBER(2) TRANSPORT MEDIA DAC7611P DAC7611U DAC7611U/2K5 DAC7611PB DAC7611UB DAC7611UB/2K5 Rails Rails Tape and Reel Rails Rails Tape and Reel NOTES: (1) For detailed drawing and dimension table, please see end of data sheet, or Appendix C of Burr-Brown IC Data Book. (2) Models with a slash (/) are available only in Tape and Reel in the quantities indicated (e.g., /2K5 indicates 2500 devices per reel). Ordering 2500 pieces of “DAC7611/2K5” will get a single 2500-piece Tape and Reel. For detailed Tape and Reel mechanical information, refer to Appendix B of Burr-Brown IC Data Book. ® 3 DAC7611 EQUIVALENT INPUT LOGIC ESD protection diodes to VDD and GND DAC Switches 12 CLR Force to 000H DAC Register LD Latched Transparent 12 Data SDI Serial Shift Register CS CLK ® DAC7611 4 TIMING DIAGRAMS (MSB) SDI (LSB) D11 D10 D9 D8 D7 D6 D5 D4 D3 D2 D1 D0 CLK tCSS tCSH CS tLD1 tLD2 LD tDS tDH SDI tCL tCH CLK tLDW LD tCLRW CLR tS FS VOUT ZS TIMING SPECIFICATIONS LOGIC TRUTH TABLE CS(1) CLK(1) CLR LD tS ±1 LSB Error Band SERIAL SHIFT REGISTER TA = –40°C to +85°C and V DD = +5V. DAC REGISTER H X H H No Change No Change L L H H No Change No Change L H H H No Change No Change SYMBOL DESCRIPTION tCH Clock Width HIGH MIN TYP MAX UNITS 30 tCL Clock Width LOW 30 ns Load Pulse Width 20 ns ns L ↑ H H Advanced One Bit No Change tLDW ↑ L H H Advanced One Bit No Change tDS Data Setup 15 ns H(2) X H ↓ No Change Changes to Value of Serial Shift Register tDH Data Hold 15 ns tCLRW Clear Pulse Width 30 ns H(2) X H L(3) No Change Transparent tLD1 Load Setup 15 ns H X L X No Change Loaded with 000H Load Hold 10 ns H X ↑ tLD2 H No Change Latched with 000H ↑ Positive Logic Transition; ↓ Negative Logic Transition; X = Don’t Care. NOTES: (1) CS and CLK are interchangeable. (2) A HIGH value is suggested in order to avoid to “false clock” from advancing the shift register and changing the DAC voltage. (3) If data is clocked into the serial register while LD is LOW, the DAC output voltage will change, reflecting the current value of the serial shift register. tCSS Select 30 ns tCSH Deselect 20 ns NOTE: All input control signals are specified with tR = tF = 5ns (10% to 90% of +5V) and timed from a voltage level of 1.6V. These parameters are guaranteed by design and are not subject to production testing. ® 5 DAC7611 TYPICAL PERFORMANCE CURVES At TA = +25°, and VDD = 5V, unless otherwise specified. PULL-DOWN VOLTAGE vs OUTPUT SINK CURRENT OUTPUT SWING vs LOAD 1k 5 100 RL tied to AGND Data = FFFH Delta VOUT (mV) Output Voltage (V) 4 3 2 25°C 10 1 RL tied to +5V Data = 000H 1 85°C (mV) –40°C 0.1 Data = 000H 0.01 0.001 0 10 100 1k 10k 100k 0.01 0.1 1 10 100 Current (mA) Load Resistance (Ω) SUPPLY CURRENT vs LOGIC INPUT VOLTAGE BROADBAND NOISE 4.0 No Load Supply Current (mA) Noise Voltage (500µV/div) 3.2 Code = FFFH BW = 2MHz 2.4 1.6 0.8 0 0 Time (2ms/div) 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 Logic Voltage (V) POWER SUPPLY REJECTION vs FREQUENCY MINIMUM SUPPLY VOLTAGE vs LOAD 70 5.0 Data = FFFH VDD = 5V ±200mV AC 60 4.8 VDD Minimum (V) 50 PSR (dB) ∆VFS = 1 LSB Data = FFFH 40 30 20 4.6 4.4 4.2 10 0 10 100 1k 10k 100k 4.0 0.010 1M Frequency (Hz) ® DAC7611 0.100 1.000 Output Load Current (mA) 6 10.000 TYPICAL PERFORMANCE CURVES (CONT) At TA = +25°, and VDD = 5V, unless otherwise specified. SHORT-CIRCUIT CURRENT vs OUTPUT VOLTAGE SUPPLY CURRENT vs TEMPERATURE 80 4.0 Positive Current Limit Supply Current (mA) 40 VLOGIC = 2.4V Data = FFFH No Load 3.5 Data = 800H Output tied to ISOURCE 20 0 –20 –40 Negative Current Limit –60 3.0 2.5 2.0 VDD = 5.25V VDD = 5.0V 1.5 1.0 0.5 –80 VDD = 4.75V 0 0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 –50 –25 0 25 50 75 100 Output Voltage (V) Temperature (°C) MIDSCALE GLITCH PERFORMANCE MIDSCALE GLITCH PERFORMANCE 125 LD VOUT (10mV/div) VOUT (10mV/div) LD VOUT VOUT 800H to 7FFH 7FFH to 800H Time (500ns/div) Time (500ns/div) LARGE-SIGNAL SETTLING TIME RISE TIME DETAIL CL = 110pF RL = No Load Output Voltage (1mV/div) LD 1V/div Output Current (mA) 60 VOUT LD Time (20µs/div) VOUT Time (10µs/div) ® 7 DAC7611 TYPICAL PERFORMANCE CURVES (CONT) At TA = +25°, and VDD = 5V, unless otherwise specified. FALL TIME DETAIL OUTPUT VOLTAGE NOISE vs FREQUENCY 10.000 Noise (µV/√Hz) Output Voltage (1mV/div) Data = FFFH VOUT LD 1.000 0.100 0.010 Time (10µs/div) 10 100 1k 10k 100k Frequency (Hz) LONG-TERM DRIFT ACCELERATED BY BURN-IN 5 TOTAL UNADJUSTED ERROR HISTOGRAM 60 120 Units T.U.E = ΣINL = ZS + FS Sample Size = 300 Units TA = +25°C 50 3 2 1 min 0 avg –1 Number of Units Output Voltage Change (mV) 4 max –2 –3 40 30 20 10 –4 –5 0 200 400 600 800 1000 0 –12 1200 –8 –4 0 4 8 12 Hours of Operation at +150°C FULL-SCALE VOLTAGE vs TEMPERATURE ZERO-SCALE VOLTAGE vs TEMPERATURE 4.115 3 4.105 2 Zero-Scale (mV) Full-Scale Output (V) No Load Sample Size = 300 Avg + 3σ 4.110 4.100 4.095 Avg 4.090 4.085 1 0 4.080 Avg – 3σ 4.075 –1 –50 –25 0 25 50 75 100 125 –50 Temperature (°C) 0 25 50 Temperature (°C) ® DAC7611 –25 8 75 100 125 TYPICAL PERFORMANCE CURVES (CONT) At TA = +25°, and VDD = 5V, unless otherwise specified. LINEARITY ERROR vs DIGITAL CODE (at +25°C) 2.0 1.5 1.5 Linearity Error (LSBs) 2.0 1.0 0.5 0 –0.5 –1.0 1.0 0.5 0 –0.5 –1.0 –1.5 –1.5 –2.0 –2.0 0 512 1024 1536 2048 2560 3072 3584 0 4096 512 1024 1536 2048 2560 3072 3584 4096 Code Code LINEARITY ERROR vs DIGITAL CODE (at –40°C) 2.0 1.5 Linearity Error (LSBs) Linearity Error (LSBs) LINEARITY ERROR vs DIGITAL CODE (at +85°C) 1.0 0.5 0 –0.5 –1.0 –1.5 –2.0 0 512 1024 1536 2048 2560 3072 3584 4096 Code ® 9 DAC7611 OPERATION clear input (CLR) is provided to simplify start-up or periodic resets. Table I shows the relationship between input code and output voltage. The digital data into the DAC7611 is double-buffered. This means that new data can be entered into the DAC without disturbing the old data and the analog output of the converter. At some point after the data has been entered into the serial shift register, this data can be transferred into the DAC register. This transfer is accomplished with a HIGH to LOW transition of the LD pin. However, the LD pin makes the DAC register transparent. If new data is shifted into the shift register while LD is LOW, the DAC output voltage will change as each new bit is entered. To prevent this, LD must be returned HIGH prior to shifting in new serial data. At any time, the contents of the DAC register can be set to 000H (analog output equals 0V) by taking the CLR input LOW. The DAC register will remain at this value until CLR is returned HIGH and LD is taken LOW to allow the contents of the shift register to be transferred to the DAC register. If LD is LOW when CLR is taken LOW, the DAC register will be set to 000H and the analog output driven to 0V. When CLR is returned HIGH, the DAC register will be set to the current value in the serial shift register and the analog output will respond accordingly. The DAC7611 is a 12-bit digital-to-analog converter (DAC) complete with a serial-to-parallel shift register, DAC register, laser-trimmed 12-bit DAC, on-board reference, and a rail-to-rail output amplifier. Figure 1 shows the basic operation of the DAC7611. INTERFACE Figure 1 shows the basic connection between a microcontroller and the DAC7611. The interface consists of a serial clock (CLK), serial data (SDI), and a load strobe signal (LD). In addition, a chip select (CS) input is available to enable serial communication when there are multiple serial devices. The data format is Straight Binary and is loaded MSB-first into the shift registers. An asynchronous DAC7611 Full-Scale Range = 4.095V Least Significant Bit = 1mV DIGITAL INPUT CODE STRAIGHT BINARY ANALOG OUTPUT (V) FFFH 801H 800H 7FFH 000H DESCRIPTION +4.095 +2.049 +2.048 +2.047 0 Full Scale Midscale + 1 LSB Midscale Midscale – 1 LSB Zero Scale DIGITAL-TO-ANALOG CONVERTER The internal DAC section is a 12-bit voltage output device that swings between ground and the internal reference voltage. The DAC is realized by a laser-trimmed R-2R ladder network which is switched by N-channel MOSFETs. The DAC output is internally connected to the rail-to-rail output operational amplifier. TABLE I. Digital Input Code and Corresponding Ideal Analog Output. +5V DAC7611 1 VDD VOUT 8 2 CS GND 7 Serial Clock 3 CLK CLR 6 Serial Data 4 SDI LD 5 10µF From µC + 0.1µF 0V to +4.095V OUTPUT AMPLIFIER A precision, low-power amplifier buffers the output of the DAC section and provides additional gain to achieve a 0 to 4.095V range. The amplifier has low offset voltage, low noise, and a set gain of 1.682V/V (4.095/2.435). See Figure 2 for an equivalent circuit schematic of the analog portion of the DAC7611. Load Strobe FIGURE 1. Basic Operation of the DAC7611. R-2R DAC 2R Output Amplifier R Buffer Bandgap Reference 2R R2 2.435V R R1 2R R 2R 2R FIGURE 2. Simplified Schematic of Analog Portion. ® DAC7611 10 The output amplifier has a 7µs typical settling time to ±1 LSB of the final value. Note that there are differences in the settling time for negative-going signals versus positivegoing signals. The DAC7611 power supply should be bypassed as shown in Figure 1. The bypass capacitors should be placed as close to the device as possible, with the 0.1uF capacitor taking priority in this regard. The Power Supply Rejection vs Frequency graph in the Typical Performance Curves section shows the PSRR performance of the DAC7611. This should be taken into account when using switching power supplies or DC/DC converters. The rail-to-rail output stage of the amplifier provides the full-scale range of 0V to 4.095V while operating on a supply voltage as low as 4.75V. In addition to its ability to drive resistive loads, the amplifier will remain stable while driving capacitive loads of up to 500pF. See Figure 3 for an equivalent circuit schematic of the amplifier’s output driver and the Typical Performance Curves section for more information regarding settling time, load driving capability, and output noise. In addition to offering guaranteed performance with VDD in the 4.75V to 5.25V range, the DAC7611 will operate with reduced performance down to 4.5V. Operation between 4.5V and 4.75V will result in longer settling time, reduced performance, and current sourcing capability. Consult the VDD vs Load Current graph in the Typical Performance Curves section for more information. APPLICATIONS VDD POWER AND GROUNDING P-Channel The DAC7611 can be used in a wide variety of situations— from low power, battery operated systems to large-scale industrial process control systems. In addition, some applications require better performance than others, or are particularly sensitive to one or two specific parameters. This diversity makes it difficult to define definite rules to follow concerning the power supply, bypassing, and grounding. The following discussion must be considered in relation to the desired performance and needs of the particular system. A precision analog component requires careful layout, adequate bypassing, and a clean, well-regulated power supply. As the DAC7611 is a single-supply, +5V component, it will often be used in conjunction with digital logic, microcontrollers, microprocessors, and digital signal processors. The more digital logic present in the design and the higher the switching speed, the more difficult it will be to achieve good performance. Because the DAC7611 has a single ground pin, all return currents, including digital and analog return currents, must flow through this pin. The GND pin is also the ground reference point for the internal bandgap reference. Ideally, GND would be connected directly to an analog ground plane. This plane would be separate from the ground connection for the digital components until they are connected at the power entry point of the system (see Figure 4). VOUT N-Channel AGND FIGURE 3. Simplified Driver Section of Output Amplifier. POWER SUPPLY A BiCMOS process and careful design of the bipolar and CMOS sections of the DAC7611 result in a very low power device. Bipolar transistors are used where tight matching and low noise are needed to achieve analog accuracy, and CMOS transistors are used for logic, switching functions and for other low power stages. If power consumption is critical, it is important to keep the logic levels on the digital inputs (SDI, CLK, CS, LD, CLR) as close as possible to either VDD or ground. This will keep the CMOS inputs (see “Supply Current vs Logic Input Voltages” in the Typical Performance Curves) from shunting current between VDD and ground. Thus, CMOS logic levels rather than TTL logic levels, are strongly recommended for driving the DAC7611. The power applied to VDD should be well regulated and lownoise. Switching power supplies and DC/DC converters will often have high-frequency glitches or spikes riding on the output voltage. In addition, digital components can create similar high frequency spikes as their internal logic switches states. This noise can easily couple into the DAC output voltage through various paths between VDD and VOUT. ® 11 DAC7611 OFFSET ERROR MEASUREMENT As with most DACs, the DAC7611 can have an offset error (or zero scale error) which is either negative or positive. If the error is positive, the output voltage for an input code of 000H will be greater than 0V. If the error is negative, the output voltage is below 0V. However, since the DAC7611 is a single-supply device and cannot swing below ground, the output voltage will be 0V, giving the impression that the offset error is zero. Since measuring the offset error on a DAC is such a common task, a method is needed to reliably measure the offset error of the DAC7611. This can easily be done as shown in Figure 5. The resistor between VOUT and a negative voltage provides the output amplifier some ability to swing below ground. As with the GND connection, VDD should be connected to a +5V power supply plane or trace that is separate from the connection for digital logic until they are connected at the power entry point. In addition, the 10µF and 0.1µF capacitors shown in Figure 4 are strongly recommended and should be installed as close to VDD and ground as possible. In some situations, additional bypassing may be required such as a 100µF electrolytic capacitor or even a “Pi” filter made up of inductors and capacitors—all designed to essentially lowpass filter the +5V supply, removing the high frequency noise (see Figure 4). Digital Circuits +5V Power Supply +5V +5V GND DAC7611 GND + 100µF + VDD 0.1µF 10µF GND Optional Other Analog Components FIGURE 4. Suggested Power and Ground Connections for a DAC7611 Sharing a +5V Supply with a Digital System. +5V DAC7611 10µF + 1 VDD VOUT 8 2 CS GND 7 3 CLK CLR 6 4 SDI LD 5 0.1µF i ≤ 200µA R –V FIGURE 5. Offset Error Measurement Circuit. ® DAC7611 12