® DAC7612 DAC 761 2 Dual, 12-Bit Serial Input DIGITAL-TO-ANALOG CONVERTER FEATURES DESCRIPTION ● LOW POWER: 3.7mW ● FAST SETTLING: 7µs to 1 LSB The DAC7612 is a dual, 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, a dual DAC, and high speed rail-to-rail output amplifiers. For a fullscale step, each output will settle to 1 LSB within 7µs while only consuming 3.7mW. ● 1mV LSB WITH 4.095V FULL-SCALE RANGE ● COMPLETE WITH REFERENCE ● 12-BIT LINEARITY AND MONOTONICITY OVER INDUSTRIAL TEMP RANGE ● 3-WIRE INTERFACE: Up to 20MHz Clock The synchronous serial interface is compatible with a wide variety of DSPs and microcontrollers. Clock (CLK), Serial Data In (SDI), Chip Select (CS) and Load DACs (LOADDACS) comprise the serial interface. ● SMALL PACKAGE: 8-Lead SOIC APPLICATIONS ● PROCESS CONTROL The DAC7612 is available in an 8-lead SOIC package and is fully specified over the industrial temperature range of –40°C to +85°C. ● DATA ACQUISITION SYSTEMS ● CLOSED-LOOP SERVO-CONTROL ● PC PERIPHERALS ● PORTABLE INSTRUMENTATION VDD 12-Bit DAC A VOUTA 12 DAC Register A LOADDACS 12 CS CLK 14-Bit Serial Shift Register SDI 12 Ref DAC Register B 12 12-Bit DAC B VOUTB DAC7612 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/ • Cable: BBRCORP • Telex: 066-6491 • FAX: (520) 889-1510 • Immediate Product Info: (800) 548-6132 © 1999 Burr-Brown Corporation PDS-1501A Printed in U.S.A. June, 1999 SPECIFICATIONS At TA = –40°C to +85°C, and VDD = +5V, unless otherwise noted. DAC7612U PARAMETER CONDITIONS RESOLUTION MIN DAC7612UB TYP MAX Guaranteed Monotonic Code 000H Code 000H Code FFFH Code FFFH ANALOG OUTPUT Output Current Load Regulation Capacitive Load Short-Circuit Current Short-Circuit Duration Code 800H RLOAD ≥ 402Ω, Code 800H No Oscillation ±1/2 ±1/2 +1 1/2 4.095 1/2 –2 –1 –1 4.079 ±5 ±7 1 500 ±15 Indefinite GND or VDD DIGITAL INPUT Data Format Data Coding Logic Family Logic Levels VIH VIL IIH IIL TYP +2 +1 +3 –1 –1 ✻ 4.111 4.087 ✻ 3 Bits ±1/4 ±1/4 ✻ 1/2 4.095 1/2 ✻ ✻ ✻ ✻ ✻ +4.75 TEMPERATURE RANGE Specified Performance –40 +5.0 0.75 3.5 0.0025 LSB LSB LSB LSB V LSB mA LSB pF mA +5.25 1.5 7.5 0.002 ✻ +85 ✻ ✻ ✻ ✻ ✻ V V µA µA µs nV-s nV-s ✻ ✻ ✻ 7 2.5 0.5 V IH = 5V, VIL = 0V, No Load, at Code 000H VIH = 5V, VIL = 0V, No Load ∆VDD = ±5% ✻ ✻ ✻ ✻ 0.3 • VDD ±10 ±10 POWER SUPPLY VDD IDD Power Dissipation Power Supply Sensitivity +1 +1 ✻ 2 4.103 2 ✻ 0.7 • VDD To ±1 LSB of Final Value UNITS ✻ ✻ ✻ Serial Straight Binary CMOS DYNAMIC PERFORMANCE Settling Time(2) (tS) DAC Glitch Digital Feedthrough MAX ✻ 12 ACCURACY Relative Accuracy(1) Differential Nonlinearity Zero-Scale Error Zero Scale Match Full-Scale Voltage Full-Scale Match MIN ✻ ✻ ✻ ✻ V mA mW %/% ✻ °C ✻ Same specification as for DAC7612U. 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. ® DAC7612 2 PIN CONFIGURATION PIN DESCRIPTIONS Top View PIN SO-8 LABEL 1 SDI 1 CLK 2 LOADDACS 3 CS 4 DAC7612U 8 VOUTA 7 VDD 6 GND 5 VOUTB DESCRIPTION SDI Serial Data Input. Data is clocked into the internal serial register on the rising edge of CLK. 2 CLK 3 LOADDACS Synchronous Clock for the Serial Data Input. Loads the internal DAC registers. All DAC registers are transparent latches and are transparent when LOADDACS is LOW (regardless of the state of CS or CLK). 4 CS 5 VOUTB DAC B Output Voltage 6 GND Ground 7 VDD Positive Power Supply 8 VOUTA DAC A Output Voltage ABSOLUTE MAXIMUM RATINGS(1) Chip Select. Active LOW. ELECTROSTATIC DISCHARGE SENSITIVITY 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 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. 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) DAC7612U ±2 ±1 –40°C to +85°C SO-8 182 " " " " " " DAC7612UB ±1 ±1 –40°C to +85°C SO-8 182 " " " " " " ORDERING NUMBER(2) TRANSPORT MEDIA DAC7612U DAC7612U/2K5 DAC7612UB DAC7612UB/2K5 Rails Tape and Reel 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 “DAC7612U/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 DAC7612 EQUIVALENT INPUT LOGIC ESD protection diodes to VDD and GND DAC Switches 12 DAC B Register LOADDACS 12 Data SDI Serial Shift Register CS 12 DAC A Register CLK 12 DAC Switches ® DAC7612 4 TIMING DIAGRAMS (MSB) SDI A0 A1 (LSB) D11 D10 D9 D8 D7 D6 D5 D4 D3 D2 D1 D0 CLK tCSS tCSH CS tLD1 tLD2 LOADDACS tDS tDH SDI tCL tCH CLK tLDW LOADDACS tS FS ±1 LSB Error Band VOUT ZS LOGIC TRUTH TABLE TIMING SPECIFICATIONS SERIAL SHIFT DAC REGISTER REGISTER A TA = –40°C to +85°C and VDD = +5V. DAC REGISTER B A1 A0 CLK CS LOADDACS X X X H H No Change No Change No Change X X ↑ L H Shifts One Bit No Change No Change L No Change Loads Serial Data Word SYMBOL DESCRIPTION tCH Clock Width HIGH MIN TYP MAX UNITS 30 ns Loads Serial Data Word tCL Clock Width LOW 30 ns L X X H(1) tLDW Load Pulse Width 20 ns H L X H L No Change Loads Serial Data Word No Change tDS Data Setup 15 ns 15 ns H X H L No Change No Change Loads Serial Data Word tDH Data Hold H t LD1 Load Setup 15 ns ↑ Positive Logic Transition; X = Don’t Care. NOTE: (1) A HIGH value is suggested in order to avoid to “false clock” from advancing the shift register and changing the DAC voltage. t LD2 Load Hold 10 ns tCSS Select 30 ns t CSH 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 2.5V. These parameters are guaranteed by design and are not subject to production testing. DATA INPUT TABLE B0 B1 B2 B3 B4 B5 B6 B7 B8 B9 B10 B11 B12 B13 A1 A0 D11 D10 D9 D8 D7 D6 D5 D4 D3 D2 D1 D0 ® 5 DAC7612 TYPICAL PERFORMANCE CURVES At TA = +25°, and VDD = 5V, unless otherwise specified. PULL-DOWN VOLTAGE vs OUTPUT SINK CURRENT OUTPUT SWING vs LOAD 5 1k +85°C 100 RL tied to GND Data = FFFH Delta VOUT (mV) Output Voltage (V) 4 3 2 1 10 +25°C 1 –40°C 0.1 RL tied to VDD Data = 000H Data = 000H 0 10 100 1k 10k 0.01 0.001 100k 0.01 0.1 Load Resistance (Ω) 1 10 100 Current (mA) BROADBAND NOISE SUPPLY CURRENT vs LOGIC INPUT VOLTAGE 4.0 Supply Current (mA) Noise Voltage (500µV/div) 3.5 3.0 2.5 2.0 1.5 1.0 0.5 0 0 Time (2ms/div) Code = FFFH, BW = 1MHz 2 3 4 5 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) 1 40 30 20 4.6 4.4 4.2 10 0 10 100 1k 10k 100k 4.0 0.01 1M Frequency (Hz) ® DAC7612 0.1 1 Output Load Current (mA) 6 10 TYPICAL PERFORMANCE CURVES (CONT) At TA = +25°, and VDD = 5V, unless otherwise specified. SHORT-CIRCUIT CURRENT vs OUTPUT VOLTAGE SUPPLY CURRENT vs TEMPERATURE 2.0 20 Supply Current (mA) 1.6 Data = 800H Output tied to ISOURCE 5 0 –5 –10 Negative Current Limit –15 VDD = 5.25V 1.4 1.2 1.0 VDD = 4.75V 0.8 0.6 0.4 At worst-case digital inputs. 0.2 0 –20 0 1 2 3 4 5 6 –50 –30 –10 10 30 50 70 90 Output Voltage (V) Temperature (°C) MIDSCALE GLITCH PERFORMANCE MIDSCALE GLITCH PERFORMANCE LOADDACS 110 130 VOUT (5mV/div) VOUT (5mV/div) LOADDACS 7FFH to 800H 800H to 7FFH Time (500ns/div) Time (500ns/div) LARGE-SIGNAL SETTLING TIME RISE TIME DETAIL LOADDACS CL = 100pF RL = No Load VOUT (1mV/div) CL = 100pF RL = No Load VOUT (1V/div) Output Current (mA) 10 VDD = 5.0V VLOGIC = 3.5V Data = FFFH No Load 1.8 Positive Current Limit 15 LOADDACS Time (10µs/div) Time (20µs/div) ® 7 DAC7612 TYPICAL PERFORMANCE CURVES (CONT) At TA = +25°, and VDD = 5V, unless otherwise specified. FALL TIME DETAIL OUTPUT VOLTAGE NOISE vs FREQUENCY 10.000 CL = 100pF RL = No Load VOUT (1mV/div) Noise (µV/√Hz) Data = FFFH 1.000 0.100 LOADDACS 0.010 Time (10µs/div) 10 100 1k 10k 100k Frequency (Hz) TOTAL UNADJUSTED ERROR HISTOGRAM LONG-TERM DRIFT ACCELERATED BY BURN-IN 35 4 Max 3 2 1 Avg 0 –1 –2 T.U.E = Σ (INL + ZSE + FSE) Sample Size = 200 Units TA = +25°C 30 Number of Units Output Voltage Change at FS (mV) 5 Min –3 25 20 15 10 5 –4 0 –5 0 168 336 504 672 840 1008 –12 –10 –8 –6 –4 –2 0 2 4 6 8 10 12 Hours of Operation at +150°C FULL-SCALE VOLTAGE vs TEMPERATURE ZERO-SCALE VOLTAGE vs TEMPERATURE 4.111 3 Avg + 3σ Zero-Scale Output (mV) Full-Scale Output (V) Avg + 3σ 4.103 Avg 4.095 4.087 2 Avg 1 Avg – 3σ 0 Avg – 3σ 4.079 –1 –40 –15 10 35 60 85 –40 Temperature (°C) 10 35 Temperature (°C) ® DAC7612 –15 8 60 85 TYPICAL PERFORMANCE CURVES (CONT) At TA = +25°, and VDD = 5V, unless otherwise specified. LINEARITY ERROR vs DIGITAL CODE (DAC B at +85°C) 2.0 2.0 1.5 1.5 1.0 Linearity Error (LSBs) Linearity Error (LSBs) LINEARITY ERROR vs DIGITAL CODE (DAC A at +85°C) 0.5 0 –0.5 –1.0 –1.5 0 –0.5 –1.0 –2.0 0 512 1024 1536 2048 2560 3072 3584 4096 0 512 1024 1536 2048 2560 3072 Code Code LINEARITY ERROR vs DIGITAL CODE (DAC A at +25°C) LINEARITY ERROR vs DIGITAL CODE (DAC B at +25°C) 2.0 2.0 1.5 1.5 Linearity Error (LSBs) Linearity Error (LSBs) 0.5 –1.5 –2.0 1.0 0.5 0 –0.5 –1.0 3584 4096 3584 4096 3584 4096 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 Code Code LINEARITY ERROR vs DIGITAL CODE (DAC A at –40°C) LINEARITY ERROR vs DIGITAL CODE (DAC B at –40°C) 2.0 2.0 1.5 1.5 1.0 Linearity Error (LSBs) Linearity Error (LSBs) 1.0 0.5 0 –0.5 –1.0 –1.5 1.0 0.5 0 –0.5 –1.0 –1.5 –2.0 –2.0 0 512 1024 1536 2048 2560 3072 3584 4096 0 Code 512 1024 1536 2048 2560 3072 Code ® 9 DAC7612 next 12 bits are the code (MSB-first) sent to the DAC. The data format is Straight Binary and is loaded MSB-first into the shift registers after loading the address bits. Table I shows the relationship between input code and output voltage. OPERATION The DAC7612 is a dual, 12-bit digital-to-analog converter (DAC) complete with a serial-to-parallel shift register, DAC registers, laser-trimmed 12-bit DACs, on-board reference, and rail-to-rail output amplifiers. Figure 1 shows the basic operation of the DAC7612. The digital data into the DAC7612 is double-buffered. This means that new data can be entered into the chosen 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 registers. This transfer is accomplished with a HIGH to LOW transition of the LOADDACS pin. The LOADDACS pin makes the DAC registers transparent. If new data is shifted into the shift register while LOADDACS is LOW, the DAC output voltages will change as each new bit is entered. To prevent this, LOADDACS must be returned HIGH prior to shifting in new serial data. INTERFACE Figure 1 shows the basic connection between a microcontroller and the DAC7612. The interface consists of a Serial Clock (CLK), Serial Data (SDI), and a Load DAC signal (LOADDACS). In addition, a chip select (CS) input is available to enable serial communication when there are multiple serial devices. Loading either DAC A or DAC B is done by shifting 14 serial bits in via the SDI input. The first 2 bits represent the address of the DAC to be updated and the 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. Each DAC output is internally connected to a rail-to-rail output operational amplifier. DAC7612 Full-Scale Range = 4.095V Least Significant Bit = 1mV DIGITAL INPUT CODE STRAIGHT OFFSETBINARY ANALOG OUTPUT (V) DESCRIPTION FFFH +4.095 801H +2.049 Full Scale Midscale + 1 LSB 800H +2.048 Midscale 7FFH +2.047 Midscale – 1 LSB 000H 0 OUTPUT AMPLIFIER A precision, low-power amplifier buffers the output of each DAC section and provides additional gain to achieve a 0V to 4.095V range. Each amplifier has low offset voltage, low Zero Scale TABLE I. Digital Input Code and Corresponding Ideal Analog Output. DAC7612U Serial Data 1 SDI VOUTA 8 Serial Clock 2 CLK VDD 7 Load DACs 3 LOADDACS GND 6 Chip Select 4 CS VOUTB 5 0V to +4.095V 0.1µF FIGURE 1. Basic Operation of the DAC7612. ® DAC7612 10 + 10µF 0V to +4.095V If power consumption is critical, it is important to keep the logic levels on the digital inputs (SDI, CLK, CS, LOADDACS) 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. 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 DAC7612. 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 rail-to-rail output stage of the amplifier provides the fullscale 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. The DAC7612 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 0.1µF 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 DAC7612. This should be taken into account when using switching power supplies or DC/DC converters. In addition to offering guaranteed performance with VDD in the 4.75V to 5.25V range, the DAC7612 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. POWER SUPPLY A BiCMOS process and careful design of the bipolar and CMOS sections of the DAC7612 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. R-2R DAC 2R Output Amplifier R Buffer Bandgap Reference 2R R2 2.435V R R1 2R R 2R Typical of DAC A or DAC B 2R FIGURE 2. Simplified Schematic of Analog Portion. VDD P-Channel VOUT N-Channel GND FIGURE 3. Simplified Driver Section of Output Amplifier. ® 11 DAC7612 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). APPLICATIONS POWER AND GROUNDING The DAC7612 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. 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. 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). A precision analog component requires careful layout, adequate bypassing, and a clean, well-regulated power supply. As the DAC7612 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 DAC7612 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 Digital Circuits +5V Power Supply +5V +5V GND DAC7612 GND 100µF + + VDD 10µF 0.1µF GND Optional Other Analog Components FIGURE 4. Suggested Power and Ground Connections for a DAC7612 Sharing a +5V Supply with a Digital System. ® DAC7612 12