AD5744R

Complete Quad, 14-Bit, High Accuracy, Serial Input, Bipolar Voltage Output DAC AD5744R FEATURES Complete quad, 14-bit digital-to-analog converter (DAC) Programmable output range: ±10 V, ±10.2564 V, or ±10.5263 V ±1 LSB maximum INL error, ±1 LSB maximum DNL error Low noise: 60 nV/√Hz Settling time: 10 μs maximum Integrated reference buffers Internal reference: 10 ppm/°C maximum On-chip die temperature sensor Output control during power-up/brownout Programmable short-circuit protection Simultaneous updating via LDAC Asynchronous CLR to zero code Digital offset and gain adjust Logic output control pins DSP-/microcontroller-compatible serial interface Temperature range: −40°C to +85°C iCMOS process technology GENERAL DESCRIPTION The AD5744R is a quad, 14-bit, serial input, bipolar voltage output DAC that operates from supply voltages of ±11.4 V to ±16.5 V. Nominal full-scale output range is ±10 V. The AD5744R provides integrated output amplifiers, reference buffers, and proprietary power-up/power-down control circuitry. The part also features a digital I/O port, programmed via the serial interface, and an analog temperature sensor. The part incorporates digital offset and gain adjust registers per channel. The AD5744R is a high performance converter that provides guaranteed monotonicity, integral nonlinearity (INL) of ±1 LSB, low noise, and 10 μs settling time. The AD5744R includes an onchip 5 V reference with a reference temperature coefficient of 10 ppm/°C maximum. During power-up when the supply voltages are changing, VOUTx is clamped to 0 V via a low impedance path. The AD5744R is based on the iCMOS® technology platform, which is designed for analog systems designers within industrial/instrumentation equipment OEMs who need high performance ICs at higher voltage levels. iCMOS enables the development of analog ICs capable of 30 V and operation at ±15 V supplies, while allowing reductions in power consumption and package size, coupled with increased ac and dc performance. The AD5744R uses a serial interface that operates at clock rates of up to 30 MHz and is compatible with DSP and microcontroller interface standards. Double buffering allows the simultaneous updating of all DACs. The input coding is programmable to either twos complement or offset binary formats. The asynchronous clear function clears all DAC registers to either bipolar zero or zero scale, depending on the coding used. The AD5744R is ideal for both closed-loop servo control and open-loop control applications. The AD5744R is available in a 32-lead TQFP and offers guaranteed specifications over the −40°C to +85°C industrial temperature range (see Figure 1 for the functional block diagram). APPLICATIONS Industrial automation Open-loop/closed-loop servo control Process control Data acquisition systems Automatic test equipment Automotive test and measurement High accuracy instrumentation Rev. A Information furnished by Analog Devices is believed to be accurate and reliable. However, no responsibility is assumed by Analog Devices for its use, nor for any infringements of patents or other rights of third parties that may result from its use. Specifications subject to change without notice. No license is granted by implication or otherwise under any patent or patent rights of Analog Devices. Trademarks and registered trademarks are the property of their respective owners. One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A. Tel: 781.329.4700 www.analog.com Fax: 781.461.3113 ©2008 Analog Devices, Inc. All rights reserved. AD5744R TABLE OF CONTENTS Features .............................................................................................. 1  Applications ....................................................................................... 1  General Description ......................................................................... 1  Revision History ............................................................................... 2  Functional Block Diagram .............................................................. 3  Specifications..................................................................................... 4  AC Performance Characteristics ................................................ 6  Timing Characteristics ................................................................ 7  Absolute Maximum Ratings.......................................................... 10  Thermal Resistance .................................................................... 10  ESD Caution ................................................................................ 10  Pin Configuration and Function Descriptions ........................... 11  Typical Performance Characteristics ........................................... 13  Terminology .................................................................................... 19  Theory of Operation ...................................................................... 21  DAC Architecture ....................................................................... 21  Reference Buffers ........................................................................ 21  Serial Interface ............................................................................ 21  Simultaneous Updating via LDAC ........................................... 23  Transfer Function ....................................................................... 23  Asynchronous Clear (CLR) ....................................................... 23  Registers ........................................................................................... 24  Function Register ....................................................................... 24  Data Register ............................................................................... 25  Coarse Gain Register ................................................................. 25  Fine Gain Register ...................................................................... 25  Design Features ............................................................................... 26  Analog Output Control ............................................................. 26  Programmable Short-Circuit Protection ................................ 26  Digital I/O Port ........................................................................... 26  Die Temperature Sensor ............................................................ 26  Local Ground Offset Adjust ...................................................... 26  Applications Information .............................................................. 27  Typical Operating Circuit ......................................................... 27  Layout Guidelines ........................................................................... 29  Galvanically Isolated Interface ................................................. 29  Microprocessor Interfacing ....................................................... 29  Outline Dimensions ....................................................................... 30  Ordering Guide .......................................................................... 30  REVISION HISTORY 12/08—Rev. 0 to Rev. A Changes to Figure 1 .......................................................................... 3 10/08—Revision 0: Initial Version Rev. A | Page 2 of 32 AD5744R FUNCTIONAL BLOCK DIAGRAM PGND DVCC DGND AVDD AVSS AVDD AVSS REFOUT REFGND REFAB VOLTAGE MONITOR AND CONTROL RSTOUT RSTIN AD5744R 14 5V REFERENCE REFERENCE BUFFERS ISCC SDIN SCLK SYNC SDO INPUT SHIFT REGISTER AND CONTROL LOGIC INPUT REG A DAC REG A 14 DAC A G1 VOUTA G2 GAIN REG A AGNDA 14 DAC B G2 G1 VOUTB INPUT REG B DAC REG B GAIN REG B D0 D1 INPUT REG C DAC REG C 14 DAC C G2 GAIN REG C BIN/2sCOMP INPUT REG D DAC REG D 14 DAC D G2 CLR GAIN REG D REFERENCE BUFFERS TEMP SENSOR G1 G1 AGNDB VOUTC AGNDC VOUTD AGNDD LDAC REFCD TEMP Figure 1. Rev. A | Page 3 of 32 06065-001 AD5744R SPECIFICATIONS AVDD = 11.4 V to 16.5 V, AVSS = −11.4 V to −16.5 V, AGND = DGND = REFGND = PGND = 0 V; REFAB = REFCD = 5 V external; DVCC = 2.7 V to 5.25 V, RLOAD = 10 kΩ, CL = 200 pF. All specifications TMIN to TMAX, unless otherwise noted. Table 1. Parameter ACCURACY Resolution Relative Accuracy (INL) Differential Nonlinearity (DNL) Bipolar Zero Error Min 14 −1 −1 −2 −3 Typ Max Unit Bits LSB LSB mV mV Test Conditions/Comments 1 Outputs unloaded +1 +1 +2 +3 Guaranteed monotonic 25°C; error at other temperatures obtained using bipolar zero tempco Bipolar Zero Tempco 2 Zero-Scale Error −2 −2 −2.5 −2 −0.02 −2 +2 +2 +2.5 +2 +0.02 +2 0.125 ppm FSR/°C mV mV ppm FSR/°C % FSR ppm FSR/°C LSB 25°C; error at other temperatures obtained using zero-scale tempco Zero-Scale Tempco2 Gain Error Gain Tempco2 DC Crosstalk2 REFERENCE INPUT/OUTPUT Reference Input2 Reference Input Voltage DC Input Impedance Input Current Reference Range Reference Output Output Voltage Reference Tempco2 RLOAD2 Power Supply Sensitivity1 Output Noise2 Noise Spectral Density2 Output Voltage Drift vs. Time2 Thermal Hysteresis1 OUTPUT CHARACTERISTICS2 Output Voltage Range 3 Output Voltage Drift vs. Time Short-Circuit Current Load Current Capacitive Load Stability RLOAD = ∞ RLOAD = 10 kΩ DC Output Impedance 5 1 −10 1 4.995 −10 1 5 ±1.7 300 18 75 ±40 ±50 70 30 −10.5263 −14.7368 ±13 ±15 10 −1 +1 200 1000 0.3 +10.5263 +14.7368 +10 7 5.005 +10 V MΩ μA V V ppm/°C MΩ μV/V μV p-p nV/√Hz ppm/500 hr ppm/1000 hr ppm ppm V V ppm FSR/500 hr ppm FSR/1000 hr mA mA pF pF Ω ±1% for specified performance Typically 100 MΩ Typically ±30 nA 25°C, AVDD/AVSS = ±13.5 V 0.1 Hz to 10 Hz 10 kHz First temperature cycle Subsequent temperature cycles AVDD/AVSS = ±11.4 V, REFIN = 5 V AVDD/AVSS = ±16.5 V, REFIN = 7 V RISCC = 6 kΩ, see Figure 31 For specified performance Rev. A | Page 4 of 32 AD5744R Parameter DIGITAL INPUTS 2 Min 2.4 −1.2 Typ Max Unit V V μA pF V V V V μA pF Test Conditions/Comments 1 DVCC = 2.7 V to 5.25 V Input High Voltage, VIH Input Low Voltage, VIL Input Current Pin Capacitance DIGITAL OUTPUTS (D0, D1, SDO)2 Output Low Voltage Output High Voltage Output Low Voltage Output High Voltage High Impedance Leakage Current High Impedance Output Capacitance DIE TEMPERATURE SENSOR2 Output Voltage at 25°C Output Voltage Scale Factor Output Voltage Range Output Load Current Power-On Time POWER REQUIREMENTS AVDD AVSS DVCC Power Supply Sensitivity2 ∆VOUT/∆ΑVDD AIDD AISS DICC Power Dissipation 1 2 0.8 +1.2 10 0.4 Per pin Per pin DVCC = 5 V ± 5%, sinking 200 μA DVCC = 5 V ± 5%, sourcing 200 μA DVCC = 2.7 V to 3.6 V, sinking 200 μA DVCC = 2.7 V to 3.6 V, sourcing 200 μA SDO only SDO only DVCC − 1 0.4 DVCC − 0.5 −1 5 +1 1.47 5 1.175 80 +11.4 −11.4 2.7 −85 3.55 2.8 1.2 275 +16.5 −16.5 5.25 1.9 200 V mV/°C V μA ms V V dB mA/channel mA/channel mA mW Die temperature −40°C to +105°C Current source only Outputs unloaded Outputs unloaded VIH = DVCC, VIL = DGND, 750 μA typ ±12 V operation output unloaded Temperature range: −40°C to +85°C; typical at +25°C. Device functionality is guaranteed to 105°C with degraded performance. Guaranteed by design and characterization; not production tested. 3 Output amplifier headroom requirement is 1.4 V minimum. Rev. A | Page 5 of 32 AD5744R AC PERFORMANCE CHARACTERISTICS AVDD = 11.4 V to 16.5 V, AVSS = −11.4 V to −16.5 V, AGND = DGND = REFGND = PGND = 0 V; REFAB = REFCD = 5 V external; DVCC = 2.7 V to 5.25 V, RLOAD = 10 kΩ, CL = 200 pF. All specifications TMIN to TMAX, unless otherwise noted. Table 2. Parameter DYNAMIC PERFORMANCE 1 Output Voltage Settling Time Min Typ 8 10 Slew Rate Digital-to-Analog Glitch Energy Glitch Impulse Peak Amplitude Channel-to-Channel Isolation DAC-to-DAC Crosstalk Digital Crosstalk Digital Feedthrough Output Noise (0.1 Hz to 10 Hz) Output Noise (0.1 Hz to 100 kHz) 1/f Corner Frequency Output Noise Spectral Density Complete System Output Noise Spectral Density 2 1 2 Max Unit μs μs μs V/μs nV-sec mV dB nV-sec nV-sec nV-sec LSB p-p μV rms kHz nV/√Hz nV/√Hz Test Conditions/Comments Full-scale step to ±1 LSB 512 LSB step settling 2 5 8 25 80 8 2 2 0.025 45 1 60 80 Effect of input bus activity on DAC outputs Measured at 10 kHz Measured at 10 kHz Guaranteed by design and characterization; not production tested. Includes noise contributions from integrated reference buffers, 14-bit DAC, and output amplifier. Rev. A | Page 6 of 32 AD5744R TIMING CHARACTERISTICS AVDD = 11.4 V to 16.5 V, AVSS = −11.4 V to −16.5 V, AGND = DGND = REFGND = PGND = 0 V; REFAB = REFCD = 5 V external; DVCC = 2.7 V to 5.25 V, RLOAD = 10 kΩ, CL = 200 pF. All specifications TMIN to TMAX, unless otherwise noted. Table 3. Parameter 1, 2, 3 t1 t2 t3 t4 t5 4 t6 t7 t8 t9 t10 t11 t12 t13 t14 t15 5, 6 t16 t17 t18 1 2 3 Limit at TMIN, TMAX 33 13 13 13 13 40 2 5 1.7 480 10 500 10 10 2 25 13 2 170 Unit ns min ns min ns min ns min ns min ns min ns min ns min μs min ns min ns min ns max μs max ns min μs max ns max ns min μs max ns min Description SCLK cycle time SCLK high time SCLK low time SYNC falling edge to SCLK falling edge setup time 24th SCLK falling edge to SYNC rising edge Minimum SYNC high time Data setup time Data hold time SYNC rising edge to LDAC falling edge (all DACs updated) SYNC rising edge to LDAC falling edge (single DAC updated) LDAC pulse width low LDAC falling edge to DAC output response time DAC output settling time CLR pulse width low CLR pulse activation time SCLK rising edge to SDO valid SYNC rising edge to SCLK falling edge SYNC rising edge to DAC output response time (LDAC = 0) LDAC falling edge to SYNC rising edge Guaranteed by design and characterization; not production tested. All input signals are specified with tR = tF = 5 ns (10% to 90% of DVCC) and timed from a voltage level of 1.2 V. See Figure 2, Figure 3, and Figure 4. 4 Standalone mode only. 5 Measured with the load circuit of Figure 5. 6 Daisy-chain mode only. Rev. A | Page 7 of 32 AD5744R Timing Diagrams t1 SCLK 1 2 24 t6 t4 SYNC t3 t2 t5 t7 SDIN DB23 t8 DB0 t10 LDAC t9 t10 t18 VOUTx t12 t11 LDAC = 0 t12 VOUTx t17 CLR t13 t14 06065-002 VOUTx Figure 2. Serial Interface Timing Diagram t1 SCLK 24 48 t6 t4 SYNC t3 t2 t5 t16 t7 SDIN DB23 t8 DB0 DB23 DB0 INPUT WORD FOR DAC N SDO t15 DB23 INPUT WORD FOR DAC N–1 DB0 UNDEFINED LDAC INPUT WORD FOR DAC N t9 t10 06065-003 Figure 3. Daisy-Chain Timing Diagram Rev. A | Page 8 of 32 AD5744R SCLK 24 48 SYNC SDIN DB23 DB0 DB23 DB0 INPUT WORD SPECIFIES REGISTER TO BE READ SDO DB23 NOP CONDITION DB0 06065-004 UNDEFINED SELECTED REGISTER DATA CLOCKED OUT Figure 4. Readback Timing Diagram 200µA IOL TO OUTPUT PIN CL 50pF 200µA IOH VOH (MIN) OR VOL (MAX) 06065-005 Figure 5. Load Circuit for SDO Timing Diagram Rev. A | Page 9 of 32 AD5744R ABSOLUTE MAXIMUM RATINGS TA = 25°C, unless otherwise noted. Transient currents of up to 100 mA do not cause SCR latch-up. Table 4. Parameter AVDD to AGND, DGND AVSS to AGND, DGND DVCC to DGND Digital Inputs to DGND Digital Outputs to DGND REFIN to AGND, PGND REFOUT to AGND TEMP VOUTx to AGND AGND to DGND Operating Temperature Range Industrial Storage Temperature Range Junction Temperature (TJ max) Lead Temperature (Soldering) Rating −0.3 V to +17 V +0.3 V to −17 V −0.3 V to +7 V −0.3 V to (DVCC + 0.3 V) or +7 V, whichever is less −0.3 V to DVCC + 0.3 V −0.3 V to AVDD + 0.3 V AVSS to AVDD AVSS to AVDD AVSS to AVDD −0.3 V to +0.3 V Stresses above those listed under Absolute Maximum Ratings may cause permanent damage to the device. This is a stress rating only; functional operation of the device at these or any other conditions above those indicated in the operational section of this specification is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability. THERMAL RESISTANCE θJA is specified for the worst-case conditions, that is, a device soldered in a circuit board for surface-mount packages. Table 5. Thermal Resistance Package Type 32-Lead TQFP θJA 65 θJC 12 Unit °C/W ESD CAUTION −40°C to +85°C −65°C to +150°C 150°C JEDEC Industry Standard J-STD-020 Rev. A | Page 10 of 32 AD5744R PIN CONFIGURATION AND FUNCTION DESCRIPTIONS BIN/2sCOMP REFGND REFOUT REFCD REFAB TEMP AVDD AVSS 32 31 30 29 28 27 26 25 SYNC 1 SCLK 2 SDIN 3 SDO 4 CLR 5 LDAC 6 D0 7 D1 8 9 10 11 12 13 14 15 16 PIN 1 24 23 22 21 20 19 18 17 AGNDA VOUTA VOUTB AGNDB AGNDC VOUTC VOUTD AGNDD AD5744R TOP VIEW (Not to Scale) RSTIN RSTOUT PGND DVCC DGND AVDD AVSS ISCC Figure 6. Pin Configuration Table 6. Pin Function Descriptions Pin No. 1 2 3 4 5 6 Mnemonic SYNC SCLK SDIN SDO CLR LDAC Description Active Low Input. This is the frame synchronization signal for the serial interface. While SYNC is low, data is transferred in on the falling edge of SCLK. Serial Clock Input. Data is clocked into the shift register on the falling edge of SCLK. This operates at clock speeds of up to 30 MHz. Serial Data Input. Data must be valid on the falling edge of SCLK. Serial Data Output. This pin is used to clock data from the serial register in daisy-chain or readback mode. Negative Edge Triggered Input. 1 Asserting this pin sets the DAC registers to 0x0000. Load DAC. This logic input is used to update the DAC registers and, consequently, the analog outputs. When tied permanently low, the addressed DAC register is updated on the rising edge of SYNC. If LDAC is held high during the write cycle, the DAC input register is updated, but the output update is held off until the falling edge of LDAC. In this mode, all analog outputs can be updated simultaneously on the falling edge of LDAC. The LDAC pin must not be left unconnected. Digital I/O Port. D0 and D1 form a digital I/O port. The user can set up these pins as inputs or outputs that are configurable and readable over the serial interface. When configured as inputs, these pins have weak internal pull-ups to DVCC. When programmed as outputs, D0 and D1 are referenced by DVCC and DGND. Reset Logic Output. This is the output from the on-chip voltage monitor used in the reset circuit. If desired, it can be used to control other system components. Reset Logic Input. This input allows external access to the internal reset logic. Applying a Logic 0 to this input clamps the DAC outputs to 0 V. In normal operation, RSTIN should be tied to Logic 1. Register values remain unchanged. Digital Ground Pin. Digital Supply Pin. Voltage ranges from 2.7 V to 5.25 V. Positive Analog Supply Pins. Voltage ranges from 11.4 V to 16.5 V. Ground Reference Point for Analog Circuitry. Negative Analog Supply Pins. Voltage ranges from –11.4 V to –16.5 V. This pin is used in association with an optional external resistor to AGND to program the short-circuit current of the output amplifiers. Refer to the Design Features section for more information. Ground Reference Pin for DAC D Output Amplifier. Analog Output Voltage of DAC D. Buffered output with a nominal full-scale output range of ±10 V. The output amplifier is capable of directly driving a 10 kΩ, 200 pF load. Analog Output Voltage of DAC C. Buffered output with a nominal full-scale output range of ±10 V. The output amplifier is capable of directly driving a 10 kΩ, 200 pF load. Ground Reference Pin for DAC C Output Amplifier. Ground Reference Pin for DAC B Output Amplifier. Analog Output Voltage of DAC B. Buffered output with a nominal full-scale output range of ±10 V. The output amplifier is capable of directly driving a 10 kΩ, 200 pF load. 7, 8 D0, D1 9 10 11 12 13, 31 14 15, 30 16 17 18 19 20 21 22 RSTOUT RSTIN DGND DVCC AVDD PGND AVSS ISCC AGNDD VOUTD VOUTC AGNDC AGNDB VOUTB Rev. A | Page 11 of 32 06065-006 AD5744R Pin No. 23 24 25 26 27 28 29 32 Mnemonic VOUTA AGNDA REFAB REFCD REFOUT REFGND TEMP BIN/2sCOMP Description Analog Output Voltage of DAC A. Buffered output with a nominal full-scale output range of ±10 V. The output amplifier is capable of directly driving a 10 kΩ, 200 pF load. Ground Reference Pin for DAC A Output Amplifier. External Reference Voltage Input for Channel A and Channel B. The reference input range is 1 V to 7 V, and it programs the full-scale output voltage. REFIN = 5 V for specified performance. External Reference Voltage Input for Channel C and Channel D. The reference input range is 1 V to 7 V, and it programs the full-scale output voltage. REFIN = 5 V for specified performance. Reference Output. This is the reference output from the internal voltage reference. The internal reference is 5 V ± 3 mV at 25°C, with a reference temperature coefficient of 10 ppm/°C. Reference Ground Return for the Reference Generator and Buffers. This pin provides an output voltage proportional to temperature. The output voltage is 1.47 V typical at 25°C die temperature; variation with temperature is 5 mV/°C. This pin determines the DAC coding. This pin should be hardwired to either DVCC or DGND. When hardwired to DVCC, input coding is offset binary (see Table 7). When hardwired to DGND, input coding is twos complement (see Table 8). 1 Internal pull-up device on this logic input. Therefore, it can be left floating; and it defaults to a logic high condition. Rev. A | Page 12 of 32 AD5744R TYPICAL PERFORMANCE CHARACTERISTICS 0.25 0.20 0.15 DNL ERROR (LSB) TA = 25°C VDD/VSS = ±15V REFIN = 5V 0.25 0.20 0.15 0.10 0.05 0 –0.05 –0.10 –0.15 –0.20 06065-009 TA = 25°C VDD/VSS = ±12V REFIN = 5V 0.10 INL ERROR (LSB) 0.05 0 –0.05 –0.10 –0.15 –0.20 –0.25 0 2000 4000 6000 8000 10,000 12,000 14,000 16,000 0 2000 4000 6000 8000 10,000 12,000 14,000 16,000 DAC CODE DAC CODE Figure 7. Integral Nonlinearity Error vs. DAC Code, VDD/VSS = ±15 V 0.25 0.20 0.15 TA = 25°C VDD/VSS = ±12V REFIN = 5V Figure 10. Differential Nonlinearity Error vs. DAC Code, VDD/VSS = ±12 V 0.12 0.10 0.08 0.10 INL ERROR (LSB) INL ERROR (LSB) 0.05 0 –0.05 –0.10 –0.15 –0.20 06065-010 0.06 0.04 0.02 0 –0.02 0 2000 4000 6000 8000 10,000 12,000 14,000 16,000 20 40 60 80 100 DAC CODE TEMPERATURE (°C) Figure 8. Integral Nonlinearity Error vs. DAC Code, VDD/VSS = ±12 V 0.25 0.20 0.15 TA = 25°C VDD/VSS = ±15V REFIN = 5V Figure 11. Integral Nonlinearity Error vs. Temperature, VDD/VSS = ±15 V 0.12 0.10 0.08 DNL ERROR (LSB) 0.10 INL ERROR (LSB) 0.05 0 –0.05 –0.10 –0.15 –0.20 06065-013 0.06 0.04 0.02 0 –0.02 0 2000 4000 6000 8000 10,000 12,000 14,000 16,000 20 40 60 80 100 DAC CODE TEMPERATURE (°C) Figure 9. Differential Nonlinearity Error vs. DAC Code, VDD/VSS = ±15 V Figure 12. Integral Nonlinearity Error vs. Temperature, VDD/VSS = ±12 V Rev. A | Page 13 of 32 06065-016 –0.25 VDD/VSS = ±12V REFIN = 5V –0.04 –40 –20 0 06065-015 –0.25 VDD/VSS = ±15V REFIN = 5V –0.04 –40 –20 0 06065-014 –0.25 AD5744R 0.04 VDD/VSS = ±15V 0.03 REFIN = 5V 0.02 0.05 DNL ERROR (LSB) DNL ERROR (LSB) 0.15 0.10 TA = 25°C REFIN = 5V 0.01 0 –0.01 –0.02 –0.03 –0.04 –0.05 06065-019 0 –0.05 –0.10 –0.15 –0.20 –0.25 11.4 –20 0 20 40 60 80 100 12.4 13.4 14.4 15.4 16.4 TEMPERATURE (°C) SUPPLY VOLTAGE (V) Figure 13. Differential Nonlinearity Error vs. Temperature, VDD/VSS = ±15 V 0.04 0.03 0.02 DNL ERROR (LSB) Figure 16. Differential Nonlinearity Error vs. Supply Voltage 0.20 0.15 0.10 0.01 0 –0.01 –0.02 –0.03 –0.04 –0.05 VDD/VSS = ±12V REFIN = 5V –0.06 –40 –20 0 INL ERROR (LSB) 0.05 0 –0.05 –0.10 –0.15 –0.20 TA = 25°C VDD/VSS = ±15V 1 2 3 4 5 6 7 REFERENCE VOLTAGE (V) 06065-027 06065-031 20 40 60 80 100 TEMPERATURE (°C) Figure 14. Differential Nonlinearity Error vs. Temperature, VDD/VSS = ±12 V 0.12 –0.10 –0.08 –0.06 –0.04 –0.02 0 06065-020 –0.25 Figure 17. Integral Nonlinearity Error vs. Reference Voltage VDD/VSS = ±15 V 0.10 0.08 0.06 DNL ERROR (LSB) 0.04 0.02 0 –0.02 –0.04 –0.06 INL ERROR (LSB) –0.02 –0.04 11.4 TA = 25°C REFIN = 5V 12.4 13.4 14.4 15.4 16.4 06065-023 –0.08 –0.10 1 TA = 25°C VDD/VSS = ±16.5V 2 3 4 5 6 7 REFERENCE VOLTAGE (V) SUPPLY VOLTAGE (V) Figure 15. Integral Nonlinearity Error vs. Supply Voltage Figure 18. Differential Nonlinearity Error vs. Reference Voltage VDD/VSS = ±16.5 V Rev. A | Page 14 of 32 06065-025 –0.06 –40 AD5744R 0.6 0.4 0.2 0 –0.2 TA = 25°C 0.8 REFIN = 5V 0.6 VDD/VSS = ±15V BIPOLAR ZERO ERROR (mV) 0.4 VDD/VSS = ±12V 0.2 TUE (mV) –0.4 –0.6 –0.8 –1.0 –1.2 –1.4 06065-035 0 –0.2 1 2 3 4 5 6 7 –20 0 20 40 60 80 100 REFERENCE VOLTAGE (V) TEMPERATURE (°C) Figure 19. Total Unadjusted Error vs. Reference Voltage, VDD/VSS = ±16.5 V 14 TA = 25°C REFIN = 5V 13 |IDD| 1.4 Figure 22. Bipolar Zero Error vs. Temperature REFIN = 5V 1.2 1.0 GAIN ERROR (mV) CURRENT (mA) 12 VDD/VSS = ±12V 0.8 0.6 0.4 0.2 0 –0.2 –40 11 10 |ISS| 9 VDD/VSS = ±15V 12.4 13.4 14.4 15.4 16.4 06065-037 –20 0 20 40 60 80 100 VDD/VSS (V) TEMPERATURE (°C) Figure 20. IDD/ISS vs. VDD/VSS 0.25 0.20 0.15 0.0014 REFIN = 5V VDD/VSS = ±15V 0.0013 VDD/VSS = ±12V 0.0012 0.0011 Figure 23. Gain Error vs. Temperature TA = 25°C 5V ZERO-SCALE ERROR (mV) 0.10 0.05 0 –0.05 –0.10 –0.15 –0.20 DICC (mA) 0.0010 0.0009 0.0008 3V 0.0007 0.0006 06065-038 –20 0 20 40 60 80 100 0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 TEMPERATURE (°C) VLOGIC (V) Figure 21. Zero-Scale Error vs. Temperature Figure 24. DICC vs. Logic Input Voltage Rev. A | Page 15 of 32 06065-041 –0.25 –40 06065-040 8 11.4 06065-039 –1.6 –0.4 –40 AD5744R 7000 6000 OUTPUT VOLTAGE DELTA (µV) 5000 4000 TA = 25°C REFIN = 5V VDD/VSS = ±15V VDD/VSS = ±12V –4 –6 –8 –10 –12 VOUT (mV) 3000 2000 1000 0 –1000 –10 –14 –16 –18 –20 –22 –24 VDD/VSS = ±12V, REFIN = 5V, TA = 25°C, 0x8000 TO 0x7FFF, 500ns/DIV 06065-047 –5 0 5 10 SOURCE/SINK CURRENT (mA) 06065-042 –26 –2.0–1.5–1.0–0.5 0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 TIME (µs) Figure 25. Source and Sink Capability of Output Amplifier with Positive Full Scale Loaded 10,000 TA = 25°C 9000 REFIN = 5V 8000 7000 6000 5000 4000 3000 2000 1000 0 06065-043 Figure 28. Major Code Transition Glitch Energy, VDD/VSS = ±12 V OUTPUT VOLTAGE DELTA (µV) VDD/VSS = ±15V VDD/VSS = ±15V MIDSCALE LOADED REFIN = 0V VDD/VSS = ±12V 4 –7 –2 3 8 SOURCE/SINK CURRENT (mA) CH4 50.0µV M1.00s CH4 26µV Figure 26. Source and Sink Capability of Output Amplifier with Negative Full Scale Loaded VDD/VSS = ±15V TA = 25°C REFIN = 5V Figure 29. Peak-to-Peak Noise (100 kHz Bandwidth) VDD/VSS = ±12V, REFIN = 5V, TA = 25°C, RAMP TIME = 100µs, LOAD = 200pF||10kΩ T 1 2 3 06065-044 1 1µs/DIV CH1 3.00V M1.00µs CH1 –120mV CH1 10.0V BW CH2 10.0V CH3 10.0mV BW M100µs T 29.60% A CH1 7.80mV Figure 27. Full-Scale Settling Time Figure 30. VOUTx vs. VDD/VSS on Power-Up Rev. A | Page 16 of 32 06065-055 06065-048 –1000 –12 50µV/DIV AD5744R 10 9 VDD/VSS = ±15V TA = 25°C REFIN = 5V VDD/VSS = ±12V TA = 25°C SHORT-CIRCUIT CURRENT (mA) 8 7 6 5 4 3 2 1 06065-050 1 0 20 40 60 RISCC (kΩ) 80 100 120 M1.00s A CH1 18mV Figure 31. Short-Circuit Current vs. RISCC T Figure 34. REFOUT Output Noise 0.1 Hz to 10 Hz 6 TA = 25°C VDD/VSS = ±15V VDD/VSS = ±12V TA = 25°C REFERENCE OUTPUT VOLTAGE (V) 5 1 2 4 3 2 3 1 T 29.60% 0 20 40 60 80 100 120 140 160 180 200 LOAD CURRENT (µA) Figure 32. REFOUT Turn-On Transient VDD/VSS = ±12V TA = 25°C, 10µF CAPACITOR ON REFOUT 1.9 Figure 35. REFOUT Load Regulation TA = 25°C VDD/VSS = ±15V TEMPERATURE OUTPUT VOLTAGE (V) 1.8 1.7 1.6 1.5 1.4 1.3 1.2 1.1 –20 0 20 40 60 1 06065-052 50µV/DIV CH1 50.0µV M1.00s A CH1 15µV 80 100 TEMPERATURE (°C) Figure 33. REFOUT Output Noise 100 kHz Bandwidth Figure 36. Temperature Output Voltage vs. Temperature Rev. A | Page 17 of 32 06065-033 1.0 –40 06065-032 CH1 10.0V BW CH2 10.0V CH3 5.00V BW M400µs A CH1 7.80mV 06065-054 0 06065-053 0 5µV/DIV AD5744R 5.003 20 DEVICES SHOWN 40 35 30 MAX: 10ppm/°C TYP: 1.7ppm/°C REFERENCE OUTPUT VOLTAGE (V) 5.002 POPULATION (%) 5.001 25 20 15 10 5.000 4.999 4.998 5 06065-070 06065-072 4.997 –40 –20 0 20 40 60 80 100 0 0.5 1.5 2.5 3.5 4.5 5.5 6.5 7.5 8.5 9.5 TEMPERATURE (°C) TEMPERATURE DRIFT (ppm/°C) Figure 37. Reference Output Voltage vs. Temperature Figure 38. Reference Output Temperature Drift (−40°C to +85°C) Rev. A | Page 18 of 32 AD5744R TERMINOLOGY Relative Accuracy or Integral Nonlinearity (INL) For the DAC, a measure of the maximum deviation, in LSBs, from a straight line passing through the endpoints of the DAC transfer function. Differential Nonlinearity (DNL) The difference between the measured change and the ideal 1 LSB change between any two adjacent codes. A specified differential nonlinearity of ±1 LSB maximum ensures monotonicity. This DAC is guaranteed monotonic. Monotonicity A DAC is monotonic if the output either increases or remains constant for increasing digital input code. The AD5744R is monotonic over its full operating temperature range. Bipolar Zero Error The deviation of the analog output from the ideal half-scale output of 0 V when the DAC register is loaded with 0x8000 (offset binary coding) or 0x0000 (twos complement coding). Figure 22 shows a plot of bipolar zero error vs. temperature. Bipolar Zero Temperature Coefficient The measure of the change in the bipolar zero error with a change in temperature. It is expressed as parts per million of full-scale range per degree Celsius (ppm FSR/°C). Full-Scale Error The measure of the output error when full-scale code is loaded to the DAC register. Ideally, the output voltage should be 2 × VREFIN − 1 LSB. Full-scale error is expressed as a percentage of full-scale range (% FSR). Negative Full-Scale Error/Zero-Scale Error The error in the DAC output voltage when 0x0000 (offset binary coding) or 0x8000 (twos complement coding) is loaded to the DAC register. Ideally, the output voltage should be −2 × VREFIN. Figure 21 shows a plot of zero-scale error vs. temperature. Output Voltage Settling Time The amount of time it takes for the output to settle to a specified level for a full-scale input change. Slew Rate A limitation in the rate of change of the output voltage. The output slewing speed of a voltage output DAC is usually limited by the slew rate of the amplifier used at its output. Slew rate is measured from 10% to 90% of the output signal and is given in volts per microsecond (V/μs). Gain Error A measure of the span error of the DAC. It is the deviation in slope of the DAC transfer characteristic from the ideal, expressed as a percentage of the full-scale range (% FSR). Figure 23 shows a plot of gain error vs. temperature. Total Unadjusted Error (TUE) A measure of the output error, considering all the various errors. Figure 19 shows a plot of total unadjusted error vs. reference voltage. Zero-Scale Error Temperature Coefficient A measure of the change in zero-scale error with a change in temperature. It is expressed as parts per million of full-scale range per degree Celsius (ppm FSR/°C). Gain Error Temperature Coefficient A measure of the change in gain error with changes in temperature. It is expressed as parts per million of full-scale range per degree Celsius (ppm FSR/°C). Digital-to-Analog Glitch Energy The impulse injected into the analog output when the input code in the DAC register changes state. It is normally specified as the area of the glitch in nanovolt-seconds (nV-sec) and is measured when the digital input code is changed by 1 LSB at the major carry transition (0x7FFF to 0x8000), as shown in Figure 28. Digital Feedthrough A measure of the impulse injected into the analog output of the DAC from the digital inputs of the DAC but is measured when the DAC output is not updated. It is specified in nanovolt-seconds (nV-sec) and measured with a full-scale code change on the data bus, that is, from all 0s to all 1s, and vice versa. Power Supply Sensitivity Indicates how the output of the DAC is affected by changes in the power supply voltage. DC Crosstalk The dc change in the output level of one DAC in response to a change in the output of another DAC. It is measured with a fullscale output change on one DAC while monitoring another DAC, and is expressed in least significant bits (LSBs). DAC-to-DAC Crosstalk The glitch impulse transferred to the output of one DAC due to a digital code change and subsequent output change of another DAC. This includes both digital and analog crosstalk. It is measured by loading one of the DACs with a full-scale code change (from all 0s to all 1s, and vice versa) with LDAC low and monitoring the output of another DAC. The energy of the glitch is expressed in nanovolt-seconds (nV-sec). Channel-to-Channel Isolation The ratio of the amplitude of the signal at the output of one DAC to a sine wave on the reference input of another DAC. It is measured in decibels (dB). Reference Temperature Coefficient A measure of the change in the reference output voltage with a change in temperature. It is expressed in parts per million per degree Celsius (ppm/°C). Rev. A | Page 19 of 32 AD5744R Digital Crosstalk A measure of the impulse injected into the analog output of one DAC from the digital inputs of another DAC but is measured when the DAC output is not updated. It is specified in nanovoltseconds (nV-sec) and measured with a full-scale code change on the data bus; that is, from all 0s to all 1s, and vice versa. Thermal Hysteresis The change of reference output voltage after the device is cycled through temperatures from −40°C to +85°C and back to −40°C. This is a typical value from a sample of parts put through such a cycle. Rev. A | Page 20 of 32 AD5744R THEORY OF OPERATION The AD5744R is a quad, 14-bit, serial input, bipolar voltage output DAC that operates from supply voltages of ±11.4 V to ±16.5 V and has a buffered output voltage of up to ±10.5263 V. Data is written to the AD5744R in a 24-bit word format via a 3-wire serial interface. The AD5744R also offers an SDO pin that is available for daisy chaining or readback. The AD5744R incorporates a power-on reset circuit that ensures that the DAC registers are loaded with 0x0000 at power-up. The AD5744R features a digital I/O port that can be programmed via the serial interface, an analog die temperature sensor, on-chip 10 ppm/°C voltage reference, on-chip reference buffers, and per channel digital gain and offset registers. SERIAL INTERFACE The AD5744R is controlled over a versatile 3-wire serial interface that operates at clock rates of up to 30 MHz and is compatible with SPI, QSPI™, MICROWIRE™, and DSP standards. Input Shift Register The input shift register is 24 bits wide. Data is loaded into the device, MSB first, as a 24-bit word under the control of a serial clock input, SCLK. The input register consists of a read/write bit, a reserved bit that must be set to 0, three register select bits, three DAC address bits, and 16 data bits, as shown in Table 9. The timing diagram for this operation is shown in Figure 2. Upon power-up, the DAC registers are loaded with zero code (0x0000), and the outputs are clamped to 0 V via a low impedance path. The outputs can be updated with the zero code value by asserting either LDAC or CLR. The corresponding output voltage depends on the state of the BIN/2sCOMP pin. If the BIN/2sCOMP pin is tied to DGND, the data coding is twos complement and the outputs update to 0 V. If the BIN/2sCOMP pin is tied to DVCC, the data coding is offset binary and the outputs update to negative full scale. To have the outputs power-up with zero code loaded to the outputs, the CLR pin should be held low during power-up. DAC ARCHITECTURE The DAC architecture of the AD5744R consists of a 14-bit current mode segmented R-2R DAC. The simplified circuit diagram for the DAC section is shown in Figure 39. VREF 2R 2R R R R 2R 2R 2R 2R 2R E15 E14 E1 S11 S10 S0 R/8 IOUT VOUTx 06065-060 Standalone Operation The serial interface works with both a continuous and noncontinuous serial clock. A continuous SCLK source can be used only if SYNC is held low for the correct number of clock cycles. In gated clock mode, a burst clock containing the exact number of clock cycles must be used, and SYNC must be taken high after the final clock to latch the data. The first falling edge of SYNC starts the write cycle. Exactly 24 falling clock edges must be applied to SCLK before SYNC is brought high again. If SYNC is brought high before the 24th falling SCLK edge, the data written is invalid. If more than 24 falling SCLK edges are applied before SYNC is brought high, the input data is also invalid. The input register addressed is updated on the rising edge of SYNC. For another serial transfer to take place, SYNC must be brought low again. After the end of the serial data transfer, data is automatically transferred from the input shift register to the addressed register. When the data has been transferred into the chosen register of the addressed DAC, all DAC registers and outputs can be updated by taking LDAC low. AGNDx 4 MSBs DECODED INTO 15 EQUAL SEGMENTS 12-BIT, R-2R LADDER Figure 39. DAC Ladder Structure The four MSBs of the 14-bit data-word are decoded to drive 15 switches, E1 to E15. Each of these switches connects one of the 15 matched resistors to either AGNDx or IOUT. The remaining 12 bits of the data-word drive Switch S0 to Switch S11 of the 12-bit R-2R ladder network. REFERENCE BUFFERS The AD5744R can operate with either an external or an internal reference. The reference inputs (REFAB and REFCD) have an input range of up to 7 V. This input voltage is then used to provide a buffered positive and negative reference for the DAC cores. The positive reference is given by +VREF = 2 × VREFIN The negative reference to the DAC cores is given by −VREF = −2 × VREFIN These positive and negative reference voltages (along with the gain register values) define the output ranges of the DACs. Rev. A | Page 21 of 32 AD5744R 68HC11* MOSI SCK PC7 PC6 MISO AD5744R* SDIN SCLK SYNC LDAC SDO the system requires 24 clock pulses. Therefore, the total number of clock cycles must equal 24n, where n is the total number of AD5744R devices in the chain. When the serial transfer to all devices is complete, SYNC is taken high. This latches the input data in each device in the daisy chain and prevents any further data from being clocked into the input shift register. The serial clock can be a continuous or a gated clock. A continuous SCLK source can be used only if SYNC is held low for the correct number of clock cycles. In gated clock mode, a burst clock containing the exact number of clock cycles must be used, and SYNC must be taken high after the final clock to latch the data. SDIN AD5744R* SCLK SYNC LDAC SDO Readback Operation Before a readback operation is initiated, the SDO pin must be enabled by writing to the function register and clearing the SDO disable bit; this bit is cleared by default. Readback mode is invoked by setting the R/W bit to 1 in the serial input register write. With R/W set to 1, Bit A2 to Bit A0, in association with Bit REG2, to Bit REG0, select the register to be read. The remaining data bits in the write sequence are don’t care. During the next SPI write, the data appearing on the SDO output contain the data from the previously addressed register. For a read of a single register, the NOP command can be used in clocking out the data from the selected register on SDO. The readback diagram in Figure 4 shows the readback sequence. For example, to read back the fine gain register of Channel A, implement the following sequence: 1. Write 0xA0XXXX to the input register. This write configures the AD5744R for read mode with the fine gain register of Channel A selected. Note that all the data bits, DB15 to DB0, are don’t care. Follow with a second write: an NOP condition, 0x00XXXX. During this write, the data from the fine gain register is clocked out on the SDO line; that is, data clocked out contains the data from the fine gain register in Bit DB5 to Bit DB0. SDIN AD5744R* SCLK SYNC LDAC SDO 06065-061 *ADDITIONAL PINS OMITTED FOR CLARITY. Figure 40. Daisy-Chaining the AD5744R Daisy-Chain Operation For systems that contain several devices, the SDO pin can be used to daisy-chain several devices together. This daisy-chain mode can be useful in system diagnostics and in reducing the number of serial interface lines. The first falling edge of SYNC starts the write cycle. The SCLK is continuously applied to the input shift register when SYNC is low. If more than 24 clock pulses are applied, the data ripples out of the shift register and appears on the SDO line. This data is clocked out on the rising edge of SCLK and is valid on the falling edge. By connecting the SDO of the first device to the SDIN input of the next device in the chain, a multidevice interface is constructed. Each device in 2. Rev. A | Page 22 of 32 AD5744R SIMULTANEOUS UPDATING VIA LDAC Depending on the status of both SYNC and LDAC, and after data has been transferred into the input register of the DACs, there are two ways to update the DAC registers and DAC outputs. TRANSFER FUNCTION Table 7 and Table 8 show the ideal input code to output voltage relationship for offset binary data coding and twos complement data coding, respectively. The output voltage expression for the AD5744R is given by D⎤ VOUT = −2 × VREFIN + 4 × VREFIN ⎡ ⎢ 16,384 ⎥ ⎣ ⎦ Individual DAC Updating In individual DAC updating mode, LDAC is held low while data is being clocked into the input shift register. The addressed DAC output is updated on the rising edge of SYNC. Simultaneous Updating of All DACs In simultaneous updating of all DACs mode, LDAC is held high while data is being clocked into the input shift register. All DAC outputs are updated by taking LDAC low any time after SYNC has been taken high. The update then occurs on the falling edge of LDAC. See Figure 41 for a simplified block diagram of the DAC load circuitry. OUTPUT I/V AMPLIFIER REFAB, REFCD 14-BIT DAC VOUTx where: D is the decimal equivalent of the code loaded to the DAC. VREFIN is the reference voltage applied at the REFAB and REFCD pins. ASYNCHRONOUS CLEAR (CLR) CLR is a negative edge triggered clear that allows the outputs to be cleared to either 0 V (twos complement coding) or negative full scale (offset binary coding). It is necessary to maintain CLR low for a minimum amount of time for the operation to complete (see Figure 2). When the CLR signal is returned high, the output remains at the cleared value until a new value is programmed. If CLR is at 0 V at power-on, all DAC outputs are updated with the clear value. A clear can also be initiated through software by writing the command of 0x04XXXX to the AD5744R. LDAC DAC REGISTER INPUT REGISTER SDO Figure 41. Simplified Serial Interface of Input Loading Circuitry for One DAC Channel Table 7. Ideal Output Voltage to Input Code Relationship—Offset Binary Data Coding Digital Input MSB 11 10 10 01 00 1111 0000 0000 1111 0000 1111 0000 0000 1111 0000 LSB 1111 0001 0000 1111 0000 Analog Output VOUT +2 VREF × (8191/8192) +2 VREF × (1/8192) 0V −2 VREF × (1/8192) −2 VREF × (8191/8192) Table 8. Ideal Output Voltage to Input Code Relationship—Twos Complement Data Coding Digital Input MSB 01 00 00 11 10 1111 0000 0000 1111 0000 1111 0000 0000 1111 0000 LSB 1111 0001 0000 1111 0000 Analog Output VOUT +2 VREF × (8191/8192) +2 VREF × (1/8192) 0V −2 VREF × (1/8192) −2 VREF × (8191/8192) 06065-062 SCLK SYNC SDIN INTERFACE LOGIC Rev. A | Page 23 of 32 AD5744R REGISTERS Table 9. Input Shift Register Format MSB DB23 R/W LSB DB22 0 DB21 REG2 DB20 REG1 DB19 REG0 DB18 A2 DB17 A1 DB16 A0 DB15 to DB0 Data Table 10. Input Shift Register Bit Function Descriptions Register Bit R/W REG2, REG1, REG0 Description Indicates a read from or a write to the addressed register Used in association with the address bits, determines if a read or write operation is to the data register, offset register, gain register, or function register. REG2 REG1 REG0 Function 0 0 0 Function register 0 1 0 Data register 0 1 1 Coarse gain register 1 0 0 Fine gain register Decodes the DAC channels A2 A1 A0 Channel Address 0 0 0 DAC A 0 0 1 DAC B 0 1 0 DAC C 0 1 1 DAC D 1 0 0 All DACs Data bits A2, A1, A0 Data FUNCTION REGISTER The function register is addressed by setting the three REG bits to 000. The values written to the address bits and the data bits determine the function addressed. The functions available via the function register are outlined in Table 11 and Table 12. Table 11. Function Register Options REG2 0 0 REG1 0 0 REG0 0 0 A2 0 0 A1 0 0 A0 0 1 DB15 to DB6 Don’t care DB5 Local ground offset adjust DB4 DB3 NOP, data = don’t care D1 D1 direction value Clear, data = don’t care Load, data = don’t care DB2 D0 direction DB1 D0 value DB0 SDO disable 0 0 0 0 0 0 1 1 0 0 0 1 Table 12. Explanation of Function Register Options Option NOP Local Ground Offset Adjust D0, D1 Direction D0, D1 Value Description No operation instruction used in readback operations. Set by the user to enable the local ground offset adjust function. Cleared by the user to disable the local ground offset adjust function (default). See the Design Features section for more information. Set by the user to enable the D0 and D1 pins as outputs. Cleared by the user to enable the D0 and D1 pins as inputs (default). See the Design Features section for more information. I/O port status bits. Logic values written to these locations determine the logic outputs on the D0 and D1 pins when configured as outputs. These bits indicate the status of the D0 and D1 pins when the I/O port is active as an input. When enabled as inputs, these bits are don’t cares during a write operation. Set by the user to disable the SDO output. Cleared by the user to enable the SDO output (default). Addressing this function resets the DAC outputs to 0 V in twos complement mode and negative full scale in binary mode. Addressing this function updates the DAC registers and, consequently, the analog outputs. SDO Disable Clear Load Rev. A | Page 24 of 32 AD5744R DATA REGISTER The data register is addressed by setting the three REG bits to 010. The DAC address bits select the DAC channel with which the data transfer takes place (see Table 10). The data bits are positioned in DB15 to DB2, as shown in Table 13. Table 13. Programming the Data Register REG2 0 REG1 1 REG0 0 A2 A1 A0 DAC address DB15 to DB2 14-bit DAC data DB1 X DB0 X COARSE GAIN REGISTER The coarse gain register is addressed by setting the three REG bits to 011. The DAC address bits select the DAC channel with which the data transfer takes place (see Table 10). The coarse gain register is a 2-bit register that allows the user to select the output range of each DAC as shown in Table 15. Table 14. Programming the Coarse Gain Register REG2 0 REG1 1 REG0 1 A2 A1 A0 DAC address DB15 to DB2 Don’t care DB1 CG1 DB0 CG0 Table 15. Output Range Selection Output Range ±10 V (Default) ±10.2564 V ±10.5263 V CG1 0 0 1 CG0 0 1 0 FINE GAIN REGISTER The fine gain register is addressed by setting the three REG bits to 100. The DAC address bits select the DAC channel with which the data transfer takes place (see Table 10). The AD5744R fine gain register is a 6-bit register that allows the user to adjust the gain of each DAC channel by −8 LSBs to +7.75 LSBs in 0.25 LSB steps, as shown in Table 16 and Table 17. The adjustment is made to both the positive fullscale points and the negative full-scale points simultaneously, with each point adjusted by one-half of one step. The fine gain register coding is twos complement. Table 16. Programming the Fine Gain Register REG2 1 REG1 0 REG0 0 A2 A1 A0 DAC address DB15 to DB6 Don’t care DB5 FG5 DB4 FG4 DB3 FG3 DB2 FG2 DB1 FG1 DB0 FG0 Table 17. Fine Gain Register Options Gain Adjustment +7.75 LSBs +7.5 LSBs No Adjustment (Default) −7.75 LSBs −8 LSBs FG5 0 0 0 1 1 FG4 1 1 0 0 0 FG3 1 1 0 0 0 FG2 1 1 0 0 0 FG1 1 1 0 0 0 FG0 1 0 0 1 0 Rev. A | Page 25 of 32 AD5744R DESIGN FEATURES ANALOG OUTPUT CONTROL In many industrial process control applications, it is vital that the output voltage be controlled during power-up and during brownout conditions. When the supply voltages are changing, the VOUTx pins are clamped to 0 V via a low impedance path. To prevent the output amp from being shorted to 0 V during this time, Transmission Gate G1 is also opened (see Figure 42). RSTOUT RSTIN If the ISCC pin is left unconnected, the short-circuit current limit defaults to 5 mA. It should be noted that limiting the shortcircuit current to a small value can affect the slew rate of the output when driving into a capacitive load. Therefore, the value of the short-circuit current that is programmed should take into account the size of the capacitive load being driven. DIGITAL I/O PORT The AD5744R contains a 2-bit digital I/O port (D1 and D0). These bits can be configured independently as inputs or outputs and can be driven or have their values read back via the serial interface. The I/O port signals are referenced to DVCC and DGND. When configured as outputs, they can be used as control signals to multiplexers or can be used to control calibration circuitry elsewhere in the system. When configured as inputs, the logic signals from limit switches, for example, can be applied to D0 and D1 and can be read back using the digital interface. VOLTAGE MONITOR AND CONTROL G1 VOUTA G2 AGNDA 06065-063 Figure 42. Analog Output Control Circuitry DIE TEMPERATURE SENSOR The on-chip die temperature sensor provides a voltage output that is linearly proportional to the Celsius temperature scale. Its nominal output voltage is 1.47 V at 25°C die temperature, varying at 5 mV/°C, giving a typical output range of 1.175 V to 1.9 V over the full temperature range. Its low output impedance and linear output simplify interfacing to temperature control circuitry and analog-todigital converters (ADCs). The temperature sensor is provided as more of a convenience than as a precise feature; it is intended for indicating a die temperature change for recalibration purposes. These conditions are maintained until the power supplies stabilize and a valid word is written to the DAC register. G2 then opens, and G1 closes. Both transmission gates are also externally controllable via the reset in (RSTIN) control input. For example, if RSTIN is driven from a battery supervisor chip, the RSTIN input is driven low to open G1 and close G2 on power-off or during a brownout. Conversely, the on-chip voltage detector output (RSTOUT) is also available to the user to control other parts of the system. The basic transmission gate functionality is shown in Figure 42. PROGRAMMABLE SHORT-CIRCUIT PROTECTION The short-circuit current (ISC) of the output amplifiers can be programmed by inserting an external resistor between the ISCC pin and the PGND pin. The programmable range for the current is 500 μA to 10 mA, corresponding to a resistor range of 120 kΩ to 6 kΩ . The resistor value is calculated as follows: R≈ 60 I SC LOCAL GROUND OFFSET ADJUST The AD5744R incorporates a local ground offset adjust feature that, when enabled in the function register, adjusts the DAC outputs for voltage differences between the individual DAC ground pins and the REFGND pin, ensuring that the DAC output voltages are always referenced to the local DAC ground pin. For example, if the AGNDA pin is at +5 mV with respect to the REFGND pin, and VOUTA is measured with respect to AGNDA, a −5 mV error results, enabling the local ground offset adjust feature to adjust VOUTA by +5 mV, thereby eliminating the error. Rev. A | Page 26 of 32 AD5744R APPLICATIONS INFORMATION TYPICAL OPERATING CIRCUIT Figure 43 shows the typical operating circuit for the AD5744R. The only external components needed for this precision 14-bit DAC are decoupling capacitors on the supply pins and reference inputs and an optional short-circuit current setting resistor. Because the AD5744R incorporates a voltage reference and reference buffers, it eliminates the need for an external bipolar reference and associated buffers, resulting in an overall savings in both cost and board space. In Figure 43, AVDD is connected to +15 V, and AVSS is connected to −15 V; but AVDD and AVSS can operate with supplies from ±11.4 V to ±16.5 V. In Figure 43, AGNDx is connected to REFGND. Initial accuracy error on the output voltage of an external reference could lead to a full-scale error in the DAC. Therefore, to minimize these errors, a reference with low initial accuracy error specification is preferred. Choosing a reference with an output trim adjustment, such as the ADR425, allows a system designer to trim system errors out by setting the reference voltage to a voltage other than the nominal. The trim adjustment can also be used at temperature to trim out any error. Long term drift is a measure of how much the reference output voltage drifts over time. A reference with a tight long-term drift specification ensures that the overall solution remains relatively stable over its entire lifetime. The temperature coefficient of a reference output voltage affects INL, DNL, and TUE. A reference with a tight temperature coefficient specification should be chosen to reduce the dependence of the DAC output voltage on ambient conditions. In high accuracy applications, which have a relatively low noise budget, reference output voltage noise must be considered. It is important to choose a reference with as low an output noise voltage as practical for the system resolution that is required. Precision voltage references, such as the ADR435 (XFET® design), produce low output noise in the 0.1 Hz to 10 Hz region. However, as the circuit bandwidth increases, filtering the output of the reference may be required to minimize the output noise. Precision Voltage Reference Selection To achieve the optimum performance from the AD5744R over its full operating temperature range, an external voltage reference must be used. Care must be taken in the selection of a precision voltage reference. The AD5744R has two reference inputs, REFAB and REFCD. The voltages applied to the reference inputs are used to provide a buffered positive and negative reference for the DAC cores. Therefore, any error in the voltage reference is reflected in the outputs of the device. There are four possible sources of error to consider when choosing a voltage reference for high accuracy applications: initial accuracy, temperature coefficient of the output voltage, long term drift, and output voltage noise. Table 18. Some Precision References Recommended for Use with the AD5744R Part No. ADR435 ADR425 ADR02 ADR395 AD586 Initial Accuracy (mV Maximum) ±6 ±6 ±5 ±6 ±2.5 Long-Term Drift (ppm Typical) 30 50 50 50 15 Temperature Drift (ppm/°C Maximum) 3 3 3 25 10 0.1 Hz to 10 Hz Noise (μV p-p Typical) 3.5 3.4 10 5 4 Rev. A | Page 27 of 32 AD5744R +15V –15V 10µF 100nF 10µF 100nF TEMP BIN/2sCOMP 32 31 30 29 28 27 26 25 TEMP REFGND REFOUT REFCD SYNC SCLK SDIN SDO LDAC D0 D1 1 2 3 4 5 6 7 8 SYNC SCLK SDIN SDO CLR LDAC D0 D1 BIN/2sCOMP REFAB AGNDA 24 VOUTA 23 VOUTB 22 AGNDB 21 AGNDC 20 VOUTC 19 VOUTD 18 AGNDD 17 VOUTC VOUTD VOUTA VOUTB AVDD AD5744R RSTOUT RSTIN DGND AVSS +5V PGND DVCC AVDD AVSS 10µF 9 10 11 12 13 14 15 16 100nF RSTOUT RSTIN 100nF 10µF 10µF 100nF +15V –15V Figure 43. Typical Operating Circuit Rev. A | Page 28 of 32 06065-064 +5V 10µF ISCC AD5744R LAYOUT GUIDELINES In any circuit where accuracy is important, careful consideration of the power supply and ground return layout helps to ensure the rated performance. Design the PCB on which the AD5744R is mounted such that the analog and digital sections are separated and confined to certain areas of the board. If the AD5744R is in a system where multiple devices require an AGNDx-to-DGND connection, establish the connection at one point only. Establish the star ground point as close as possible to the device. The AD5744R should have ample supply bypassing of 10 μF in parallel with 0.1 μF on each supply located as close to the package as possible, ideally right up against the device. The 10 μF capacitors are of the tantalum bead type. The 0.1 μF capacitor should have low effective series resistance (ESR) and low effective series inductance (ESI), such as the common ceramic types that provide a low impedance path to ground at high frequencies to handle transient currents due to internal logic switching. The power supply lines of the AD5744R should use as large a trace as possible to provide low impedance paths and reduce the effects of glitches on the power supply line. Shield fastswitching signals, such as clocks with digital ground to avoid radiating noise to other parts of the board; they should never be run near the reference inputs. A ground line routed between the SDIN and SCLK lines helps reduce cross-talk between them. (A ground line is not required on a multi-layer board because it has a separate ground plane; however, it is helpful to separate the lines.) It is essential to minimize noise on the reference inputs because it couples through to the DAC output. Avoid crossover of digital and analog signals. Run traces on opposite sides of the board at right angles to each other to reduce the effects of feedthrough on the board. A microstrip technique is recommended but not always possible with a double-sided board. In this technique, the component side of the board is dedicated to the ground plane, and the signal traces are placed on the solder side. GALVANICALLY ISOLATED INTERFACE In many process control applications, it is necessary to provide an isolation barrier between the controller and the unit being controlled to protect and isolate the controlling circuitry from any hazardous common-mode voltages that may occur. Isocouplers provide voltage isolation in excess of 2.5 kV. The serial loading structure of the AD5744R makes it ideal for isolated interfaces because the number of interface lines is kept to a minimum. Figure 44 shows a 4-channel isolated interface to the AD5744R using an ADuM1400 iCoupler® product. For more information on iCoupler products, refer to www.analog.com. MICROPROCESSOR INTERFACING Microprocessor interfacing to the AD5744R is accomplished using a serial bus that uses standard protocol that is compatible with microcontrollers and DSP processors. The communications channel is a 3-wire (minimum) interface consisting of a clock signal, a data signal, and a synchronization signal. The AD5744R requires a 24-bit data-word with data valid on the falling edge of SCLK. For all the interfaces, a DAC output update can be performed automatically when all the data is clocked in, or it can be done under the control of LDAC. The contents of the DAC register can be read using the readback function. MICROCONTROLLER SERIAL CLOCK OUT ADuM1400* VIA ENCODE DECODE VOA TO SCLK SERIAL DATA OUT VIB ENCODE DECODE VOB TO SDIN SYNC OUT VIC ENCODE DECODE VOC TO SYNC CONTROL OUT VID ENCODE DECODE VOD TO LDAC 06065-065 *ADDITIONAL PINS OMITTED FOR CLARITY. Figure 44. Isolated Interface Rev. A | Page 29 of 32 AD5744R OUTLINE DIMENSIONS 0.75 0.60 0.45 1.20 MAX 32 1 PIN 1 9.00 BSC SQ 25 24 TOP VIEW 1.05 1.00 0.95 0° MIN 0.20 0.09 7° 3.5° 0° 0.08 MAX COPLANARITY (PINS DOWN) 7.00 BSC SQ 8 9 16 17 0.15 0.05 SEATING PLANE VIEW A COMPLIANT TO JEDEC STANDARDS MS-026-AB A Figure 45. 32-Lead Thin Plastic Quad Flat Package [TQFP] (SU-32-2) Dimensions shown in millimeters ORDERING GUIDE Model AD5744RCSUZ 1 AD5744RCSUZ-REEL71 1 Function Quad 14-Bit DAC Quad 14-Bit DAC INL ±1 LSB Maximum ±1 LSB Maximum Temperature Range −40°C to +85°C −40°C to +85°C Internal Reference +5 V +5 V 020607-A ROTATED 90° CCW VIEW A 0.80 BSC LEAD PITCH 0.45 0.37 0.30 Package Description 32-Lead TQFP 32-Lead TQFP Package Option SU-32-2 SU-32-2 Z = RoHS Compliant Part. Rev. A | Page 30 of 32 AD5744R NOTES Rev. A | Page 31 of 32 AD5744R NOTES ©2008 Analog Devices, Inc. All rights reserved. Trademarks and registered trademarks are the property of their respective owners. D06065-0-12/08(A) Rev. A | Page 32 of 32