FEATURES FUNCTIONAL BLOCK DIAGRAM High relative accuracy (INL): ±2 LSB maximum @ 16 bits Low drift 2.5 V reference: 2 ppm/°C typical Tiny package: 3 mm × 3 mm, 16-lead LFCSP VDD GND VREF AD5686R/AD5685R/AD5684R VLOGIC INPUT REGISTER DAC REGISTER STRING DAC A SCLK SYNC SDIN SDO VOUTA BUFFER INTERFACE LOGIC Total unadjusted error (TUE): ±0.1% of FSR maximum Offset error: ±1.5 mV maximum Gain error: ±0.1% of FSR maximum High drive capability: 20 mA, 0.5 V from supply rails User selectable gain of 1 or 2 (GAIN pin) Reset to zero scale or midscale (RSTSEL pin) 1.8 V logic compatibility 50 MHz SPI with readback or daisy chain Low glitch: 0.5 nV-sec Robust 4 kV HBM and 1.5 kV FICDM ESD rating Low power: 3.3 mW at 3 V 2.7 V to 5.5 V power supply −40°C to +105°C temperature range 2.5V REFERENCE INPUT REGISTER DAC REGISTER STRING DAC B VOUTB BUFFER INPUT REGISTER DAC REGISTER STRING DAC C VOUTC BUFFER INPUT REGISTER DAC REGISTER STRING DAC D VOUTD BUFFER LDAC RESET POWER-ON RESET GAIN ×1/×2 RSTSEL GAIN POWERDOWN LOGIC 10485-001 Data Sheet Quad, 16-/14-/12-Bit nanoDAC+ with 2 ppm/°C Reference, SPI Interface AD5686R/AD5685R/AD5684R Figure 1. APPLICATIONS Optical transceivers Base-station power amplifiers Process control (PLC I/O cards) Industrial automation Data acquisition systems GENERAL DESCRIPTION The AD5686R/AD5685R/AD5684R, members of the nanoDAC+® family, are low power, quad, 16-/14-/12-bit buffered voltage output DACs. The devices include a 2.5 V, 2 ppm/°C internal reference (enabled by default) and a gain select pin giving a full-scale output of 2.5 V (gain = 1) or 5 V (gain = 2). All devices operate from a single 2.7 V to 5.5 V supply, are guaranteed monotonic by design, and exhibit less than 0.1% FSR gain error and 1.5 mV offset error performance. The devices are available in a 3 mm × 3 mm LFCSP and a TSSOP package. The AD5686R/AD5685R/AD5684R also incorporate a poweron reset circuit and a RSTSEL pin that ensures that the DAC outputs power up to zero scale or midscale and remains there until a valid write takes place. Each part contains a per-channel power-down feature that reduces the current consumption of the device to 4 μA at 3 V while in power-down mode. Table 1. Quad nanoDAC+ Devices Interface SPI I2C Reference Internal Internal 16-Bit AD5686R AD5696R 14-Bit AD5685R AD5695R 12-Bit AD5684R AD5694R PRODUCT HIGHLIGHTS 1. 2. 3. High Relative Accuracy (INL). AD5686R (16-bit): ±2 LSB maximum AD5685R (14-bit): ±1 LSB maximum AD5684R (12-bit): ±1 LSB maximum Low Drift 2.5 V On-Chip Reference. 2 ppm/°C typical temperature coefficient 5 ppm/°C maximum temperature coefficient Two Package Options. 3 mm × 3 mm, 16-lead LFCSP 16-lead TSSOP The AD5686R/AD5685R/AD5684R employ a versatile SPI interface that operates at clock rates up to 50 MHz, and all devices contain a VLOGIC pin intended for 1.8 V/3 V/5 V logic. Rev. 0 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 ©2012 Analog Devices, Inc. All rights reserved. AD5686R/AD5685R/AD5684R Data Sheet TABLE OF CONTENTS Features .............................................................................................. 1 Write and Update Commands .................................................. 22 Applications ....................................................................................... 1 Daisy-Chain Operation ............................................................. 23 Functional Block Diagram .............................................................. 1 Readback Operation .................................................................. 23 General Description ......................................................................... 1 Power-Down Operation ............................................................ 24 Product Highlights ........................................................................... 1 Load DAC (Hardware LDAC Pin) ........................................... 25 Revision History ............................................................................... 2 LDAC Mask Register ................................................................. 25 Specifications..................................................................................... 3 Hardware Reset (RESET) .......................................................... 26 AC Characteristics........................................................................ 5 Reset Select Pin (RSTSEL) ........................................................ 26 Timing Characteristics ................................................................ 6 Internal Reference Setup ........................................................... 26 Daisy-Chain and Readback Timing Characteristics ............... 7 Solder Heat Reflow..................................................................... 26 Absolute Maximum Ratings............................................................ 9 Long-Term Temperature Drift ................................................. 26 ESD Caution .................................................................................. 9 Thermal Hysteresis .................................................................... 27 Pin Configuration and Function Descriptions ........................... 10 Applications Information .............................................................. 28 Typical Performance Characteristics ........................................... 11 Microprocessor Interfacing ....................................................... 28 Terminology .................................................................................... 18 AD5686R/AD5685R/AD5684R to ADSP-BF531 Interface.. 28 Theory of Operation ...................................................................... 20 AD5686R/AD5685R/AD5684R to SPORT Interface ............ 28 Digital-to-Analog Converter .................................................... 20 Layout Guidelines....................................................................... 28 Transfer Function ....................................................................... 20 Galvanically Isolated Interface ................................................. 29 DAC Architecture ....................................................................... 20 Outline Dimensions ....................................................................... 30 Serial Interface ............................................................................ 21 Ordering Guide .......................................................................... 31 Standalone Operation ................................................................ 22 REVISION HISTORY 4/12—Revision 0: Initial Version Rev. 0 | Page 2 of 32 Data Sheet AD5686R/AD5685R/AD5684R SPECIFICATIONS VDD = 2.7 V to 5.5 V; 1.8 V ≤ VLOGIC ≤ 5.5 V; all specifications TMIN to TMAX, unless otherwise noted. RL = 2 kΩ; CL = 200 pF. Table 2. Parameter STATIC PERFORMANCE 2 AD5686R Resolution Relative Accuracy Differential Nonlinearity AD5685R Resolution Relative Accuracy Differential Nonlinearity AD5684R Resolution Relative Accuracy Differential Nonlinearity Zero-Code Error Offset Error Full-Scale Error Min A Grade 1 Typ Max 16 Min B Grade1 Typ Max 16 ±2 ±2 ±8 ±8 ±1 14 ±1 ±1 ±2 ±3 ±1 14 ±0.5 ±4 ±1 12 ±0.5 ±1 ±1 12 Bits LSB Test Conditions/Comments LSB Gain = 2 Gain = 1 Guaranteed monotonic by design Bits LSB LSB Guaranteed monotonic by design ±1 ±1 Bits LSB LSB mV mV % of FSR % of FSR % of FSR % of FSR µV/°C ±1 ±1 ppm Of FSR/°C 0.15 0.15 mV/V DAC code = midscale; VDD = 5 V ± 10% ±2 ±2 µV ±3 ±2 ±3 ±2 µV/mA µV Due to single channel, full-scale output change Due to load current change Due to powering down (per channel) ±0.12 0.4 +0.1 +0.01 ±2 ±1 4 ±4 ±0.2 0.4 +0.1 +0.01 ±1 ±1 1.5 ±1.5 ±0.1 Gain Error ±0.02 ±0.2 ±0.02 ±0.1 Total Unadjusted Error ±0.01 ±0.25 ±0.01 ±0.1 ±0.12 ±0.25 Offset Error Drift3 Gain Temperature Coefficient3 DC Power Supply Rejection Ratio3 Unit ±0.2 Guaranteed monotonic by design All zeros loaded to DAC register All ones loaded to DAC register External reference; gain = 2; TSSOP Internal reference; gain = 1; TSSOP DC Crosstalk3 OUTPUT CHARACTERISTICS 3 Output Voltage Range 0 0 Capacitive Load Stability Resistive Load 4 Load Regulation Short-Circuit Current 5 Load Impedance at Rails 6 Power-Up Time VREF 2 × VREF 0 0 80 80 V V nF nF kΩ µV/mA 80 80 µV/mA 40 25 2.5 40 25 2.5 mA Ω µs 2 10 1 VREF 2 × VREF 2 10 1 Rev. 0 | Page 3 of 32 Gain = 1 Gain = 2, see Figure 34 RL = ∞ RL = 1 kΩ 5 V ± 10%, DAC code = midscale; −30 mA ≤ IOUT ≤ 30 mA 3 V ± 10%, DAC code = midscale; −20 mA ≤ IOUT ≤ 20 mA See Figure 34 Coming out of power-down mode; VDD = 5 V AD5686R/AD5685R/AD5684R Parameter REFERENCE OUTPUT Output Voltage 7 Reference TC 8, 9 Output Impedance3 Min Data Sheet A Grade 1 Typ Max 2.4975 5 0.04 2.5025 20 Min B Grade1 Typ Max 2.4975 2 0.04 2.5025 5 Unit Test Conditions/Comments V ppm/°C Ω At ambient See the Terminology section Output Voltage Noise3 Output Voltage Noise Density3 12 12 240 µV p-p nV/√Hz 0.1 Hz to 10 Hz 240 Load Regulation Sourcing3 20 20 µV/mA At ambient Load Regulation Sinking3 Output Current Load Capability3 40 40 At ambient ±5 ±5 µV/mA mA Line Regulation3 3 Long-Term Stability/Drift 3 Thermal Hysteresis LOGIC INPUTS3 Input Current VINL, Input Low Voltage VINH, Input High Voltage Pin Capacitance LOGIC OUTPUTS (SDO)3 Output Low Voltage, VOL Output High Voltage, VOH Floating State Output Capacitance POWER REQUIREMENTS VLOGIC ILOGIC VDD VDD IDD Normal Mode 10 All Power-Down Modes 11 At ambient; f = 10 kHz, CL = 10 nF VDD ≥ 3 V 100 100 µV/V At ambient 12 12 ppm After 1000 hours at 125°C 125 125 ppm First cycle 25 25 ppm Additional cycles ±2 0.3 × VLOGIC µA V V pF Per pin 0.4 V V pF ISINK = 200 μA ISOURCE = 200 μA 5.5 3 5.5 5.5 V µA V V 0.7 1.3 4 mA mA µA Gain = 1 Gain = 2 VIH = VDD, VIL = GND, VDD = 2.7 V to 5.5 V Internal reference off Internal reference on, at full scale −40°C to +85°C 6 µA −40°C to +105°C ±2 0.3 × VLOGIC 0.7 × VLOGIC 0.7 × VLOGIC 2 2 0.4 VLOGIC − 0.4 VLOGIC − 0.4 4 1.8 4 5.5 3 5.5 5.5 2.7 VREF + 1.5 0.59 1.1 1 0.7 1.3 4 1.8 2.7 VREF + 1.5 0.59 1.1 1 6 Temperature range: A and B grade: −40°C to +105°C. DC specifications tested with the outputs unloaded, unless otherwise noted. Upper dead band = 10 mV and exists only when VREF = VDD with gain = 1 or when VREF/2 = VDD with gain = 2. Linearity calculated using a reduced code range of 256 to 65,280 (AD5686R), 64 to 16,320 (AD5685R), and 12 to 4080 (AD5684R). 3 Guaranteed by design and characterization; not production tested. 4 Channel A and Channel B can have a combined output current of up to 30 mA. Similarly, Channel C and Channel D can have a combined output current of up to 30 mA up to a junction temperature of 110°C. 5 VDD = 5 V. The device includes current limiting that is intended to protect the device during temporary overload conditions. Junction temperature can be exceeded during current limit. Operation above the specified maximum operation junction temperature may impair device reliability. 6 When drawing a load current at either rail, the output voltage headroom with respect to that rail is limited by the 25 Ω typical channel resistance of the output devices. For example, when sinking 1 mA, the minimum output voltage = 25 Ω × 1 mA = 25 mV (see Figure 34). 7 Initial accuracy presolder reflow is ±750 µV; output voltage includes the effects of preconditioning drift. See the Internal Reference Setup section. 8 Reference is trimmed and tested at two temperatures and is characterized from −40°C to +105°C. 9 Reference temperature coefficient calculated as per the box method. See the Terminology section for further information. 10 Interface inactive. All DACs active. DAC outputs unloaded. 11 All DACs powered down. 1 2 Rev. 0 | Page 4 of 32 Data Sheet AD5686R/AD5685R/AD5684R AC CHARACTERISTICS VDD = 2.7 V to 5.5 V; RL = 2 kΩ to GND; CL = 200 pF to GND; 1.8 V ≤ VLOGIC ≤ 5.5 V; all specifications TMIN to TMAX, unless otherwise noted. 1 Table 3. Parameter 2 Output Voltage Settling Time AD5686R AD5685R AD5684R Slew Rate Digital-to-Analog Glitch Impulse Digital Feedthrough Digital Crosstalk Analog Crosstalk DAC-to-DAC Crosstalk Total Harmonic Distortion 4 Output Noise Spectral Density Output Noise SNR SFDR SINAD Min Typ Max Unit Test Conditions/Comments 3 5 5 5 0.8 0.5 0.13 0.1 0.2 0.3 −80 300 6 90 83 80 8 8 7 µs µs µs V/µs nV-sec nV-sec nV-sec nV-sec nV-sec dB nV/√Hz µV p-p dB dB dB ¼ to ¾ scale settling to ±2 LSB ¼ to ¾ scale settling to ±2 LSB ¼ to ¾ scale settling to ±2 LSB Guaranteed by design and characterization, not production tested. See the Terminology section. 3 Temperature range is −40°C to +105°C, typical @ 25°C. 4 Digitally generated sine wave @ 1 kHz. 1 2 Rev. 0 | Page 5 of 32 1 LSB change around major carry At ambient, BW = 20 kHz, VDD = 5 V, fOUT = 1 kHz DAC code = midscale, 10 kHz; gain = 2 0.1 Hz to 10 Hz At ambient, BW = 20 kHz, VDD = 5 V, fOUT = 1 kHz At ambient, BW = 20 kHz, VDD = 5 V, fOUT = 1 kHz At ambient, BW = 20 kHz, VDD = 5 V, fOUT = 1 kHz AD5686R/AD5685R/AD5684R Data Sheet TIMING CHARACTERISTICS All input signals are specified with tR = tF = 1 ns/V (10% to 90% of VDD) and timed from a voltage level of (VIL + VIH)/2. See Figure 2. VDD = 2.7 V to 5.5 V, 1.8 V ≤ VLOGIC ≤ 5.5 V; VREFIN = 2.5 V. All specifications TMIN to TMAX, unless otherwise noted. Table 4. Parameter 1 SCLK Cycle Time SCLK High Time SCLK Low Time SYNC to SCLK Falling Edge Setup Time Data Setup Time Data Hold Time SCLK Falling Edge to SYNC Rising Edge Minimum SYNC High Time (Single, Combined or All Channel Update) SYNC Falling Edge to SCLK Fall Ignore LDAC Pulse Width Low SCLK Falling Edge to LDAC Rising Edge SCLK Falling Edge to LDAC Falling Edge RESET Minimum Pulse Width Low RESET Pulse Activation Time Power-Up Time 2 2 2.7 V ≤ VLOGIC ≤ 5.5 V Min Max 20 10 10 10 5 5 10 20 10 15 20 20 30 30 4.5 Maximum SCLK frequency is 50 MHz at VDD = 2.7 V to 5.5 V, 1.8 V ≤ VLOGIC ≤ VDD. Guaranteed by design and characterization; not production tested. Time to exit power-down to normal mode of AD5686R/AD5685R/AD5684R operation, 32nd clock edge to 90% of DAC midscale value, with output unloaded. t9 t1 SCLK t8 t3 t4 t2 t7 SYNC t6 t5 SDIN DB23 DB0 t12 t10 LDAC1 t11 LDAC2 RESET VOUT t13 t14 10485-002 1 1.8 V ≤ VLOGIC < 2.7 V Min Max 33 16 16 15 5 5 15 20 16 25 30 20 30 30 4.5 Symbol t1 t2 t3 t4 t5 t6 t7 t8 t9 t10 t11 t12 t13 t14 1ASYNCHRONOUS LDAC UPDATE MODE. 2SYNCHRONOUS LDAC UPDATE MODE. Figure 2. Serial Write Operation Rev. 0 | Page 6 of 32 Unit ns ns ns ns ns ns ns ns ns ns ns ns ns ns µs Data Sheet AD5686R/AD5685R/AD5684R DAISY-CHAIN AND READBACK TIMING CHARACTERISTICS All input signals are specified with tR = tF = 1 ns/V (10% to 90% of VDD) and timed from a voltage level of (VIL + VIH)/2. See Figure 4 and Figure 5. VDD = 2.7 V to 5.5 V, 1.8 V ≤ VLOGIC ≤ 5.5 V; VREF = 2.5 V. All specifications TMIN to TMAX, unless otherwise noted. VDD = 2.7 V to 5.5 V. Table 5. Min 40 20 20 20 5 5 10 30 30 2.7 V ≤ VLOGIC ≤ 5.5 V Max Symbol t1 t2 t3 t4 t5 t6 t7 t8 t9 t10 t115 15 10 Unit ns ns ns ns ns ns ns ns ns ns ns SYNC Rising Edge to SCLK Rising Edge t125 15 10 ns 1 Min 66 33 33 33 5 5 15 60 60 1.8 V ≤ VLOGIC < 2.7 V Max Parameter 1 SCLK Cycle Time SCLK High Time SCLK Low Time SYNC to SCLK Falling Edge Data Setup Time Data Hold Time SCLK Falling Edge to SYNC Rising Edge Minimum SYNC High Time Minimum SYNC High Time SDO Data Valid from SCLK Rising Edge SCLK Falling Edge to SYNC Rising Edge 36 25 Maximum SCLK frequency is 25 MHz or 15 MHz at VDD = 2.7 V to 5.5 V, 1.8 V ≤ VLOGIC ≤ VDD. Guaranteed by design and characterization; not production tested. Circuit and Timing Diagrams 200µA VOH (MIN) CL 20pF 200µA 10485-003 TO OUTPUT PIN IOL IOH Figure 3. Load Circuit for Digital Output (SDO) Timing Specifications SCLK 24 48 t11 t8 t12 t4 SYNC SDIN t6 DB23 DB0 INPUT WORD FOR DAC N DB23 DB0 t10 INPUT WORD FOR DAC N + 1 DB23 SDO UNDEFINED DB0 INPUT WORD FOR DAC N Figure 4. Daisy-Chain Timing Diagram Rev. 0 | Page 7 of 32 10485-004 t5 AD5686R/AD5685R/AD5684R Data Sheet t1 SCLK 24 1 t8 t4 t3 24 1 t7 t2 t9 SYNC t6 t5 DB23 DB0 DB23 INPUT WORD SPECIFIES REGISTER TO BE READ SDO DB23 DB0 NOP CONDITION t10 DB0 DB23 UNDEFINED DB0 SELECTED REGISTER DATA CLOCKED OUT Figure 5. Readback Timing Diagram Rev. 0 | Page 8 of 32 10485-005 SDIN Data Sheet AD5686R/AD5685R/AD5684R ABSOLUTE MAXIMUM RATINGS TA = 25°C, unless otherwise noted. Table 5. Parameter VDD to GND VLOGIC to GND VOUT to GND VREF to GND Digital Input Voltage to GND Operating Temperature Range Storage Temperature Range Junction Temperature 16-Lead TSSOP, θJA Thermal Impedance, 0 Airflow (4-Layer Board) 16-Lead LFCSP, θJA Thermal Impedance, 0 Airflow (4-Layer Board) Reflow Soldering Peak Temperature, Pb Free (J-STD-020) ESD 1 FICDM 1 Rating −0.3 V to +7 V −0.3 V to +7 V −0.3 V to VDD + 0.3 V −0.3 V to VDD + 0.3 V −0.3 V to VLOGIC + 0.3 V −40°C to +105°C −65°C to +150°C 125°C 112.6°C/W 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. ESD CAUTION 70°C/W 260°C 4 kV 1.5 kV Human body model (HBM) classification. Rev. 0 | Page 9 of 32 AD5686R/AD5685R/AD5684R Data Sheet PIN CONFIGURATION AND FUNCTION DESCRIPTIONS 13 RESET 14 RSTSEL 16 VOUTB 15 VREF AD5686R/AD5685R/AD5684R VOUTA 1 12 SDIN 11 SYNC VDD 3 10 SCLK 9 VLOGIC 10485-006 TOP VIEW (Not to Scale) NOTES 1. THE EXPOSED PAD MUST BE TIED TO GND. GND 4 AD5686R/ AD5685R/ AD5684R VDD 5 TOP VIEW (Not to Scale) VOUTA 3 GAIN 8 LDAC 7 SDO 6 VOUTD 5 VOUTC 4 16 RSTSEL VREF 1 VOUTB 2 Figure 6. 16-Lead LFCSP Pin Configuration 15 RESET 14 SDIN 13 SYNC 12 SCLK VOUTC 6 11 VLOGIC VOUTD 7 10 GAIN SDO 8 9 LDAC 10485-007 GND 2 Figure 7. 16-Lead TSSOP Pin Configuration Table 6. Pin Function Descriptions LFCSP 1 2 3 Pin No. TSSOP 3 4 5 Mnemonic VOUTA GND VDD 4 5 6 6 7 8 VOUTC VOUTD SDO 7 9 LDAC 8 10 GAIN 9 10 11 12 VLOGIC SCLK 11 13 SYNC 12 14 SDIN 13 15 RESET 14 16 RSTSEL 15 1 VREF 16 17 2 N/A VOUTB EPAD Description Analog Output Voltage from DAC A. The output amplifier has rail-to-rail operation. Ground Reference Point for All Circuitry on the Part. Power Supply Input. These parts can be operated from 2.7 V to 5.5 V, and the supply should be decoupled with a 10 µF capacitor in parallel with a 0.1 µF capacitor to GND. Analog Output Voltage from DAC C. The output amplifier has rail-to-rail operation. Analog Output Voltage from DAC D. The output amplifier has rail-to-rail operation. Serial Data Output. Can be used to daisy-chain a number of AD5686R/AD5685R/AD5684R devices together or can be used for readback. The serial data is transferred on the rising edge of SCLK and is valid on the falling edge of the clock. LDAC can be operated in two modes, asynchronously and synchronously. Pulsing this pin low allows any or all DAC registers to be updated if the input registers have new data. This allows all DAC outputs to simultaneously update. This pin can also be tied permanently low. Span Set Pin. When this pin is tied to GND, all four DAC outputs have a span from 0 V to VREF. If this pin is tied to VDD, all four DACs output a span of 0 V to 2 × VREF. Digital Power Supply. Voltage ranges from 1.8 V to 5.5 V. Serial Clock Input. Data is clocked into the input shift register on the falling edge of the serial clock input. Data can be transferred at rates of up to 50 MHz. Active Low Control Input. This is the frame synchronization signal for the input data. When SYNC goes low, data is transferred in on the falling edges of the next 24 clocks. Serial Data Input. This device has a 24-bit input shift register. Data is clocked into the register on the falling edge of the serial clock input. Asynchronous Reset Input. The RESET input is falling edge sensitive. When RESET is low, all LDAC pulses are ignored. When RESET is activated, the input register and the DAC register are updated with zero scale or midscale, depending on the state of the RSTSEL pin. Power-On Reset Pin. Tying this pin to GND powers up all four DACs to zero scale. Tying this pin to VDD powers up all four DACs to midscale. Reference Voltage. The AD5686R/AD5685R/AD5684R have a common reference pin. When using the internal reference, this is the reference output pin. When using an external reference, this is the reference input pin. The default for this pin is as a reference output. Analog Output Voltage from DAC B. The output amplifier has rail-to-rail operation. Exposed Pad. The exposed pad must be tied to GND. Rev. 0 | Page 10 of 32 Data Sheet AD5686R/AD5685R/AD5684R TYPICAL PERFORMANCE CHARACTERISTICS 2.5020 VDD = 5V DEVICE 1 DEVICE 2 DEVICE 3 DEVICE 4 DEVICE 5 2.5015 2.5010 50 2.5005 40 HITS VREF (V) VDD = 5.5V 0 HOUR 168 HOURS 500 HOURS 1000 HOURS 60 2.5000 30 2.4995 20 2.4990 10 2.4985 0 20 40 60 80 100 120 TEMPERATURE (°C) 0 2.498 1600 DEVICE 1 DEVICE 2 DEVICE 3 DEVICE 4 DEVICE 5 VDD = 5V TA = 25°C 1200 1000 NSD (nV/ Hz) 2.5000 2.4995 800 600 400 2.4990 200 2.4985 VDD = 5V 0 20 40 60 80 100 120 TEMPERATURE (°C) Figure 9. Internal Reference Voltage vs. Temperature (Grade A) 90 0 10 10485-109 –20 100 1k 10k 100k 1M FREQUENCY (MHz) Figure 12. Internal Reference Noise Spectral Density vs. Frequency VDD = 5V VDD = 5V TA = 25°C 80 T 60 50 1 40 30 20 0 0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 TEMPERATURE DRIFT (ppm/°C) 5.0 CH1 10µV M1.0s A CH1 160mV Figure 13. Internal Reference Noise, 0.1 Hz to 10 Hz Figure 10. Reference Output Temperature Drift Histogram Rev. 0 | Page 11 of 32 10485-112 10 10485-250 NUMBER OF UNITS 70 10485-111 VREF (V) 2.502 1400 2.5005 2.4980 –40 2.501 Figure 11. Reference Long-Term Stability/Drift 2.5020 2.5010 2.500 VREF (V) Figure 8. Internal Reference Voltage vs. Temperature (Grade B) 2.5015 2.499 10485-251 –20 10485-212 2.4980 –40 AD5686R/AD5685R/AD5684R Data Sheet 2.5000 10 VDD = 5V TA = 25°C 8 2.4999 6 4 2.4997 2 INL (LSB) VREF (V) 2.4998 2.4996 0 –2 –4 2.4995 –6 2.4994 –0.003 –0.001 0.001 0.003 –10 10485-113 2.4993 –0.005 0.005 ILOAD (A) 0 2500 7500 10000 12500 15000 16348 3125 3750 4096 CODE Figure 17. AD5685R INL Figure 14. Internal Reference Voltage vs. Load Current 2.5002 5000 10485-119 VDD = 5V TA = 25°C INTERNAL REFERENCE = 2.5V –8 10 TA = 25°C D1 8 2.5000 6 4 D3 INL (LSB) VREF (V) 2.4998 2.4996 2 0 –2 2.4994 –4 –6 D2 3.5 4.0 4.5 5.0 5.5 VDD (V) –10 0 625 0.8 6 0.6 4 0.4 2 0.2 DNL (LSB) 8 0 –2 0 –0.2 –4 –0.4 –6 –0.6 VDD = 5V TA = 25°C INTERNAL REFERENCE = 2.5V –0.8 CODE 60000 10485-118 INL (LSB) 1.0 50000 2500 Figure 18. AD5684R INL 10 40000 1875 CODE Figure 15. Internal Reference Voltage vs. Supply Voltage V = 5V –8 DD TA = 25°C INTERNAL REFERENCE = 2.5V –10 0 10000 20000 30000 1250 –1.0 0 10000 20000 30000 40000 CODE Figure 19. AD5686R DNL Figure 16. AD5686R INL Rev. 0 | Page 12 of 32 50000 60000 10485-121 3.0 10485-117 2.4990 2.5 VDD = 5V TA = 25°C INTERNAL REFERENCE = 2.5V –8 10485-120 2.4992 AD5686R/AD5685R/AD5684R 10 0.8 8 0.6 6 0.4 4 0.2 0 –0.2 2 –4 –0.6 –6 V = 5V –0.8 DD TA = 25°C INTERNAL REFERENCE = 2.5V –1.0 0 2500 5000 7500 –8 12500 15000 16383 CODE DNL –2 –0.4 VDD = 5V TA = 25°C INTERNAL REFERENCE = 2.5V –10 0 0.5 8 0.6 6 0.4 4 ERROR (LSB) 0.8 0.2 0 –0.2 3.5 4.0 4.5 5.0 –2 –6 –8 3125 3750 4096 INL DNL –0.6 CODE VDD = 5V TA = 25°C INTERNAL REFERENCE = 2.5V –10 2.7 3.2 3.7 4.2 4.7 5.2 SUPPLY VOLTAGE (V) Figure 24. INL Error and DNL Error vs. Supply Voltage Figure 21. AD5684R DNL 0.10 8 0.08 6 0.06 4 0.04 ERROR (% of FSR) 10 INL 0 DNL –2 –4 –6 0.02 0 FULL-SCALE ERROR GAIN ERROR –0.02 –0.04 –10 –40 10 60 110 TEMPERATURE (°C) Figure 22. INL Error and DNL Error vs. Temperature VDD = 5V –0.08 T = 25°C A INTERNAL REFERENCE = 2.5V –0.10 –40 –20 0 20 40 60 80 100 120 TEMPERATURE (°C) Figure 25. Gain Error and Full-Scale Error vs. Temperature Rev. 0 | Page 13 of 32 10485-127 –0.06 VDD = 5V TA = 25°C INTERNAL REFERENCE = 2.5V 10485-124 ERROR (LSB) 3.0 0 –4 –8 2.5 2 –0.4 10485-123 DNL (LSB) 10 2 2.0 Figure 23. INL Error and DNL Error vs. VREF 1.0 2500 1.5 VREF (V) Figure 20. AD5685R DNL VDD = 5V –0.8 TA = 25°C INTERNAL REFERENCE = 2.5V –1.0 0 625 1250 1875 1.0 10485-126 10000 INL 0 10485-125 ERROR (LSB) 1.0 10485-122 DNL (LSB) Data Sheet AD5686R/AD5685R/AD5684R Data Sheet 0.10 1.2 0.8 0.6 0.4 ZERO-CODE ERROR 0.2 –20 0 20 40 60 80 100 120 TEMPERATURE (°C) 0.06 0.05 0.04 0.03 0.02 0.01 0 –40 10485-128 OFFSET ERROR 0 –40 0.07 0.08 0.08 TOTAL UNADJUSTED ERROR (% of FSR) 0.10 ERROR (% of FSR) 0.06 0.04 0.02 GAIN ERROR 0 FULL-SCALE ERROR –0.04 4.7 5.2 10485-129 –0.06 SUPPLY VOLTAGE (V) 20 40 60 80 100 120 Figure 29. TUE vs. Temperature 0.10 VDD = 5V –0.08 T = 25°C A INTERNAL REFERENCE = 2.5V –0.10 2.7 3.2 3.7 4.2 0 TEMPERATURE (°C) Figure 26. Zero-Code Error and Offset Error vs. Temperature –0.02 –20 0.06 0.04 0.02 0 –0.02 –0.04 –0.06 V = 5V –0.08 T DD= 25°C A INTERNAL REFERENCE = 2.5V –0.10 2.7 3.2 3.7 4.2 4.7 5.2 SUPPLY VOLTAGE (V) 10485-132 ERROR (mV) 1.0 VDD = 5V 0.09 TA = 25°C INTERNAL REFERENCE = 2.5V 0.08 10485-131 TOTAL UNADJUSTED ERROR (% of FSR) VDD = 5V 1.4 T = 25°C A INTERNAL REFERENCE = 2.5V Figure 30. TUE vs. Supply, Gain = 1 Figure 27. Gain Error and Full-Scale Error vs. Supply 1.5 0 ZERO-CODE ERROR 0 OFFSET ERROR –0.5 –1.0 VDD = 5V TA = 25°C INTERNAL REFERENCE = 2.5V –1.5 2.7 3.2 3.7 4.2 4.7 5.2 SUPPLY VOLTAGE (V) 10485-130 ERROR (mV) 0.5 –0.01 –0.02 –0.03 –0.04 –0.05 –0.06 –0.07 –0.08 VDD = 5V –0.09 T = 25°C A INTERNAL REFERENCE = 2.5V –0.10 0 10000 20000 30000 40000 CODE Figure 28. Zero-Code Error and Offset Error vs. Supply Figure 31. TUE vs. Code Rev. 0 | Page 14 of 32 50000 60000 65535 10485-133 TOTAL UNADJUSTED ERROR (% of FSR) 1.0 Data Sheet AD5686R/AD5685R/AD5684R 7 VDD = 5V TA = 25°C EXTERNAL REFERENCE = 2.5V 25 VDD = 5V 6 TA = 25°C GAIN = 2 INTERNAL 5 REFERENCE = 2.5V 20 0xFFFF VOUT (V) HITS 4 15 0xC000 3 0x8000 2 0x4000 10 1 0x0000 0 5 560 580 600 620 640 IDD (V) –2 –0.06 10485-135 540 –0.04 –0.02 Figure 32. IDD Histogram with External Reference, 5 V 0.02 0.04 0.06 Figure 35. Source and Sink Capability at 5 V 5 VDD = 5V 30 T = 25°C A INTERNAL REFERENCE = 2.5V 25 VDD = 5V TA = 25°C 4 EXTERNAL REFERENCE = 2.5V GAIN = 1 0xFFFF 3 0xC000 VOUT (V) 20 HITS 0 LOAD CURRENT (A) 10485-138 –1 0 15 2 0x8000 1 0x4000 10 0 5 0x0000 1000 1020 1040 1060 1080 1100 1120 1140 IDD FULLSCALE (V) –2 –0.06 10485-136 0 –0.04 –0.02 0 0.02 0.04 0.06 LOAD CURRENT (A) 10485-139 –1 Figure 36. Source and Sink Capability at 3 V Figure 33. IDD Histogram with Internal Reference, VREFOUT = 2.5 V, Gain = 2 1.0 1.4 0.8 0.6 1.2 0.4 CURRENT (mA) SINKING 5V 0 –0.2 1.0 ZERO CODE 0.8 EXTERNAL REFERENCE, FULL-SCALE 0.6 SOURCING 5V –0.4 0.4 –0.6 SOURCING 2.7V –1.0 0 5 10 15 20 25 LOAD CURRENT (mA) 30 0 –40 10 60 TEMPERATURE (°C) Figure 37. Supply Current vs. Temperature Figure 34. Headroom/Footroom vs. Load Current Rev. 0 | Page 15 of 32 110 10485-140 0.2 –0.8 10485-200 ΔVOUT (V) SINKING 2.7V 0.2 FULL-SCALE AD5686R/AD5685R/AD5684R Data Sheet 2.5008 4.0 DAC A DAC B DAC C DAC D 3.5 2.5003 3.0 VOUT (V) VOUT (V) 2.5 2.0 2.4998 1.5 80 160 2.4988 10485-141 VDD = 5V 0.5 TA = 25°C INTERNAL REFERENCE = 2.5V ¼ TO ¾ SCALE 0 10 20 40 320 TIME (µs) 0 6 8 10 12 Figure 41. Digital-to-Analog Glitch Impulse 0.06 6 CH A CH B CH C CH D VDD 0.003 CH B CH C CH D 5 4 0.03 3 0.02 2 0.01 1 0 0 VOUT AC-COUPLED (V) 0.002 0.04 VDD (V) VOUT (V) 4 TIME (µs) Figure 38. Settling Time, 5.25 V 0.05 2 10485-144 CHANNEL B TA = 25°C VDD = 5.25V INTERNAL REFERENCE CODE = 7FFF TO 8000 ENERGY = 0.227206nV-sec 2.4993 1.0 0.001 0 –0.001 10 –1 15 TIME (µs) –0.002 0 5 10 15 20 10485-145 5 10485-142 TA = 25°C INTERNAL REFERENCE = 2.5V –0.01 –10 –5 0 25 TIME (µs) Figure 39. Power-On Reset to 0 V Figure 42. Analog Crosstalk, Channel A 3 CH A CH B CH C CH D SYNC T GAIN = 2 VOUT (V) 2 GAIN = 1 1 0 5 TIME (µs) 10 10485-143 0 –5 VDD = 5V TA = 25°C INTERNAL REFERENCE = 2.5V Figure 40. Exiting Power-Down to Midscale VDD = 5V TA = 25°C EXTERNAL REFERENCE = 2.5V CH1 10µV M1.0s A CH1 802mV Figure 43. 0.1 Hz to 10 Hz Output Noise Plot, External Reference Rev. 0 | Page 16 of 32 10485-146 1 Data Sheet AD5686R/AD5685R/AD5684R 4.0 0nF 0.1nF 10nF 0.22nF 4.7nF 3.9 T 3.8 VDD = 5V TA = 25°C INTERNAL REFERENCE = 2.5V VOUT (V) 3.7 1 3.6 3.5 3.4 3.3 3.2 M1.0s A CH1 10485-147 CH1 10µV 3.0 1.590 802mV 1.595 1.600 1.605 1.610 1.615 1.620 1.625 1.630 TIME (ms) 10485-150 3.1 VDD = 5V TA = 25°C INTERNAL REFERENCE = 2.5V Figure 47. Settling Time vs. Capacitive Load Figure 44. 0.1 Hz to 10 Hz Output Noise Plot, 2.5 V Internal Reference 0 1600 VDD = 5V TA = 25°C 1400 INTERNAL REFERENCE = 2.5V FULL-SCALE MIDSCALE ZERO-SCALE –10 1000 800 600 400 1k 10k 100k 1M FREQUENCY (Hz) 10485-148 100 Figure 45. Noise Spectral Density 20 –80 –100 –120 –140 –160 FREQUENCY (Hz) 10485-149 THD (dBV) –60 2000 4000 6000 8000 10000 12000 14000 16000 18000 20000 100k 1M 10M Figure 48. Multiplying Bandwidth, External Reference = 2.5 V, ±0.1 V p-p, 10 kHz to 10 MHz –40 –180 VDD = 5V TA = 25°C EXTERNAL REFERENCE = 2.5V, ±0.1V p-p FREQUENCY (Hz) –20 0 –40 –60 10k VDD = 5V TA = 25°C INTERNAL REFERENCE = 2.5V 0 –30 –50 200 0 10 –20 10485-151 BANDWIDTH (dB) NSD (nV/ Hz) 1200 Figure 46. Total Harmonic Distortion @ 1 kHz Rev. 0 | Page 17 of 32 AD5686R/AD5685R/AD5684R Data Sheet TERMINOLOGY Relative Accuracy or Integral Nonlinearity (INL) For the DAC, relative accuracy or integral nonlinearity is a measurement of the maximum deviation, in LSBs, from a straight line passing through the endpoints of the DAC transfer function. A typical INL vs. code plot is shown in Figure 16. Differential Nonlinearity (DNL) Differential nonlinearity is 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 by design. A typical DNL vs. code plot can be seen in Figure 19. Zero-Code Error Zero-code error is a measurement of the output error when zero code (0x0000) is loaded to the DAC register. Ideally, the output should be 0 V. The zero-code error is always positive in the AD5686R because the output of the DAC cannot go below 0 V due to a combination of the offset errors in the DAC and the output amplifier. Zero-code error is expressed in mV. A plot of zero-code error vs. temperature can be seen in Figure 26. Full-Scale Error Full-scale error is a measurement of the output error when fullscale code (0xFFFF) is loaded to the DAC register. Ideally, the output should be VDD − 1 LSB. Full-scale error is expressed in percent of full-scale range (% of FSR). A plot of full-scale error vs. temperature can be seen in Figure 25. Gain Error This is 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 % of FSR. Offset Error Drift This is a measurement of the change in offset error with a change in temperature. It is expressed in µV/°C. Gain Temperature Coefficient This is a measurement of the change in gain error with changes in temperature. It is expressed in ppm of FSR/°C. Offset Error Offset error is a measure of the difference between VOUT (actual) and VOUT (ideal) expressed in mV in the linear region of the transfer function. Offset error is measured on the AD5686R with Code 512 loaded in the DAC register. It can be negative or positive. Output Voltage Settling Time This is the amount of time it takes for the output of a DAC to settle to a specified level for a ¼ to ¾ full-scale input change and is measured from the rising edge of SYNC. Digital-to-Analog Glitch Impulse Digital-to-analog glitch impulse is 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 nV-sec, and is measured when the digital input code is changed by 1 LSB at the major carry transition (0x7FFF to 0x8000) (see Figure 41). Digital Feedthrough Digital feedthrough is 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 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. Reference Feedthrough Reference feedthrough is the ratio of the amplitude of the signal at the DAC output to the reference input when the DAC output is not being updated. It is expressed in dB. Noise Spectral Density This is a measurement of the internally generated random noise. Random noise is characterized as a spectral density (nV/√Hz). It is measured by loading the DAC to midscale and measuring noise at the output. It is measured in nV/√Hz. A plot of noise spectral density is shown in Figure 45. DC Crosstalk DC crosstalk is 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 full-scale output change on one DAC (or soft power-down and power-up) while monitoring another DAC kept at midscale. It is expressed in μV. DC crosstalk due to load current change is a measure of the impact that a change in load current on one DAC has to another DAC kept at midscale. It is expressed in μV/mA. Digital Crosstalk This is the glitch impulse transferred to the output of one DAC at midscale in response to a full-scale code change (all 0s to all 1s and vice versa) in the input register of another DAC. It is measured in standalone mode and is expressed in nV-sec. DC Power Supply Rejection Ratio (PSRR) This indicates how the output of the DAC is affected by changes in the supply voltage. PSRR is the ratio of the change in VOUT to a change in VDD for full-scale output of the DAC. It is measured in mV/V. VREF is held at 2 V, and VDD is varied by ±10%. Rev. 0 | Page 18 of 32 Data Sheet AD5686R/AD5685R/AD5684R Analog Crosstalk This is the glitch impulse transferred to the output of one DAC due to a change in the output of another DAC. It is measured by loading one of the input registers with a full-scale code change (all 0s to all 1s and vice versa). Then execute a software LDAC and monitor the output of the DAC whose digital code was not changed. The area of the glitch is expressed in nV-sec. DAC-to-DAC Crosstalk This is the glitch impulse transferred to the output of one DAC due to a digital code change and subsequent analog output change of another DAC. It is measured by loading the attack channel with a full-scale code change (all 0s to all 1s and vice versa), using the write to and update commands while monitoring the output of the victim channel that is at midscale. The energy of the glitch is expressed in nV-sec. Multiplying Bandwidth The amplifiers within the DAC have a finite bandwidth. The multiplying bandwidth is a measure of this. A sine wave on the reference (with full-scale code loaded to the DAC) appears on the output. The multiplying bandwidth is the frequency at which the output amplitude falls to 3 dB below the input. Total Harmonic Distortion (THD) This is the difference between an ideal sine wave and its attenuated version using the DAC. The sine wave is used as the reference for the DAC, and the THD is a measurement of the harmonics present on the DAC output. It is measured in dB. Voltage Reference TC Voltage reference TC is a measure of the change in the reference output voltage with a change in temperature. The reference TC is calculated using the box method, which defines the TC as the maximum change in the reference output over a given temperature range expressed in ppm/°C, as follows; VREFmax − VREFmin 6 TC = × 10 V TempRange × REFnom where: VREFmax is the maximum reference output measured over the total temperature range. VREFmin is the minimum reference output measured over the total temperature range. VREFnom is the nominal reference output voltage, 2.5 V. TempRange is the specified temperature range of −40°C to +105°C. Rev. 0 | Page 19 of 32 AD5686R/AD5685R/AD5684R Data Sheet THEORY OF OPERATION DIGITAL-TO-ANALOG CONVERTER VREF The AD5686R/AD5685R/AD5684R are quad 16-/14-/12-bit, serial input, voltage output DACs with an internal reference. The parts operate from supply voltages of 2.7 V to 5.5 V. Data is written to the AD5686R/AD5685R/AD5684R in a 24-bit word format via a 3-wire serial interface. The AD5686R/AD5685R/ AD5684R incorporate a power-on reset circuit to ensure that the DAC output powers up to a known output state. The devices also have a software power-down mode that reduces the typical current consumption to typically 4 µA. R R R TRANSFER FUNCTION R The internal reference is on by default. To use an external reference, only a nonreference option is available. Because the input coding to the DAC is straight binary, the ideal output voltage when using an external reference is given by 10485-053 Internal Reference where: D is the decimal equivalent of the binary code that is loaded to the DAC register as follows: 0 to 4,095 for the 12-bit device. 0 to 16,383 for the 14-bit device. 0 to 65,535 for the 16-bit device. N is the DAC resolution. Gain is the gain of the output amplifier and is set to 1 by default. This can be set to ×1 or ×2 using the gain select pin. When this pin is tied to GND, all four DAC outputs have a span from 0 V to VREF. If this pin is tied to VDD, all four DACs output a span of 0 V to 2 × VREF. DAC ARCHITECTURE The DAC architecture consists of a string DAC followed by an output amplifier. Figure 49 shows a block diagram of the DAC architecture. VREF 2.5V REF RESISTOR STRING REF (–) VOUTX GAIN (GAIN = 1 OR 2) The AD5686R/AD5685R/AD5684R have a 2.5 V, 2 ppm/°C reference, giving a full-scale output of 2.5 V or 5 V, depending on the state of the GAIN pin. The internal reference associated with the device is available at the VREF pin. This buffered reference is capable of driving external loads of up to 10 mA. Output Amplifiers The output buffer amplifier can generate rail-to-rail voltages on its output, which gives an output range of 0 V to VDD. The actual range depends on the value of VREF, the GAIN pin, offset error, and gain error. The GAIN pin selects the gain of the output. • • 10485-052 GND The AD5686R/AD5685R/AD5684R on-chip reference is on at power-up but can be disabled via a write to a control register. See the Internal Reference Setup section for details. If this pin is tied to GND, all four outputs have a gain of 1 and the output range is 0 V to VREF. If this pin is tied to VLOGIC, all four outputs have a gain of 2 and the output range is 0 V to 2 × VREF. These amplifiers are capable of driving a load of 1 kΩ in parallel with 2 nF to GND. The slew rate is 0.8 V/µs with a ¼ to ¾ scale settling time of 5 µs. REF (+) DAC REGISTER R Figure 50. Resistor String Structure D VOUT = VREF × Gain N 2 INPUT REGISTER TO OUTPUT AMPLIFIER Figure 49. Single DAC Channel Architecture Block Diagram The resistor string structure is shown in Figure 50. It is a string of resistors, each of Value R. The code loaded to the DAC register determines the node on the string where the voltage is to be tapped off and fed into the output amplifier. The voltage is tapped off by closing one of the switches connecting the string to the amplifier. Because it is a string of resistors, it is guaranteed monotonic. Rev. 0 | Page 20 of 32 Data Sheet AD5686R/AD5685R/AD5684R SERIAL INTERFACE Table 7. Command Definitions The AD5686R/AD5685R/AD5684R have a 3-wire serial interface (SYNC, SCLK, and SDIN) that is compatible with SPI, QSPI, and MICROWIRE interface standards as well as most DSPs. See Figure 2 for a timing diagram of a typical write sequence. The AD5686R/AD5685R/AD5684R contain an SDO pin to allow the user to daisy-chain multiple devices together (see the Daisy-Chain Operation section) or for readback. C3 0 0 0 0 0 0 0 0 1 1 1 … 1 Input Shift Register The input shift register of the AD5686R/AD5685R/AD5684R is 24 bits wide. Data is loaded MSB first (DB23) and the first four bits are the command bits, C3 to C0 (see Table 7), followed by the 4-bit DAC address bits, DAC A, DAC B, DAC C, DAC D (see Table 8), and finally the bit data-word. The data-word comprises 16-bit, 14-bit, or 12-bit input code, followed by zero, two or four don’t care bits for the AD5686R, AD5685R, and AD5684R, respectively (see Figure 51, Figure 52, and Figure 53). These data bits are transferred to the input register on the 24 falling edges of SCLK and are updated on the rising edge of SYNC. Command C2 C1 0 0 0 0 0 1 0 1 1 1 1 0 0 0 … 1 1 0 0 1 1 0 0 1 … 1 C0 0 1 0 1 0 1 0 1 0 1 0 … 1 Description No operation Write to Input Register n (dependent on LDAC) Update DAC Register n with contents of Input Register n Write to and update DAC Channel n Power down/power up DAC Hardware LDAC mask register Software reset (power-on reset) Internal reference setup register Set up DCEN register (daisy-chain enable) Set up readback register (readback enable) Reserved Reserved Reserved Table 8. Address Commands DAC D 0 0 0 1 0 1 Commands can be executed on individual DAC channels, combined DAC channels, or on all DACs, depending on the address bits selected. 1 Address (n) DAC C DAC B 0 0 0 1 1 0 0 0 0 1 1 1 DAC A 1 0 0 0 1 1 Any combination of DAC channels can be selected using the address bits. DB23 (MSB) C3 C2 Selected DAC Channel 1 DAC A DAC B DAC C DAC D DAC A and DAC B All DACs DB0 (LSB) C1 C0 DAC DAC DAC DAC D15 D14 D13 D12 D11 D10 D C B A D9 D8 D7 D6 D5 D4 D3 D2 D1 D0 COMMAND BITS 10485-054 DATA BITS ADDRESS BITS Figure 51. AD5686R Input Shift Register Content DB23 (MSB) C3 C2 DB0 (LSB) C1 C0 DAC DAC DAC DAC D13 D12 D11 D10 D C B A D9 D8 D7 D6 D5 D4 D3 D2 D1 D0 X X COMMAND BITS 10485-055 DATA BITS ADDRESS BITS Figure 52. AD5685R Input Shift Register Content DB23 (MSB) C3 C2 DB0 (LSB) C1 C0 DAC DAC DAC DAC D11 D10 D C B A D9 D8 D7 D6 D5 D4 D3 D2 D1 D0 X X X X COMMAND BITS 10485-056 DATA BITS ADDRESS BITS Figure 53. AD5684R Input Shift Register Content Rev. 0 | Page 21 of 32 AD5686R/AD5685R/AD5684R Data Sheet STANDALONE OPERATION WRITE AND UPDATE COMMANDS The write sequence begins by bringing the SYNC line low. Data from the SDIN line is clocked into the 24-bit input shift register on the falling edge of SCLK. After the last of 24 data bits is clocked in, SYNC should be brought high. The programmed function is then executed, that is, an LDAC-dependent change in DAC register contents and/or a change in the mode of operation. If SYNC is taken high at a clock before the 24th clock, it is considered a valid frame and invalid data may be loaded to the DAC. SYNC must be brought high for a minimum of 20 ns (single channel, see t8 in Figure 2) before the next write sequence so that a falling edge of SYNC can initiate the next write sequence. SYNC should be idled at rails between write sequences for even lower power operation of the part. The SYNC line is kept low for 24 falling edges of SCLK, and the DAC is updated on the rising edge of SYNC. Write to Input Register n (Dependent on LDAC) Command 0001 allows the user to write to each DAC’s dedicated input register individually. When LDAC is low, the input register is transparent (if not controlled by the LDAC mask register). Update DAC Register n with Contents of Input Register n Command 0010 loads the DAC registers/outputs with the contents of the input registers selected and updates the DAC outputs directly. Write to and Update DAC Channel n (Independent of LDAC) Command 0011 allows the user to write to the DAC registers and update the DAC outputs directly. When the data has been transferred into the input register of the addressed DAC, all DAC registers and outputs can be updated by taking LDAC low while the SYNC line is high. Rev. 0 | Page 22 of 32 Data Sheet AD5686R/AD5685R/AD5684R DAISY-CHAIN OPERATION For systems that contain several DACs, the SDO pin can be used to daisy-chain several devices together and is enabled through a software executable daisy-chain enable (DCEN) command. Command 1000 is reserved for this DCEN function (see Table 7). The daisy-chain mode is enabled by setting Bit DB0 in the DCEN register. The default setting is standalone mode, where DB0 = 0. Table 9 shows how the state of the bit corresponds to the mode of operation of the device. READBACK OPERATION Table 9. Daisy-Chain Enable (DCEN) Register DB0 0 1 Readback mode is invoked through a software executable readback command. If the SDO output is disabled via the daisychain mode disable bit in the control register, it is automatically enabled for the duration of the read operation, after which it is disabled again. Command 1001 is reserved for the readback function. This command, in association with selecting one of address bits, DAC A to DAC D, selects the register to read. Note that only one DAC register can be selected during readback. The remaining three address bits must be set to Logic 0. The remaining data bits in the write sequence are don’t care bits. If more than one or no bits are selected, DAC Channel A is read back by default. During the next SPI write, the data appearing on the SDO output contains the data from the previously addressed register. Description Standalone mode (default) DCEN mode AD5686R/ AD5685R/ AD5684R 68HC11* MOSI SDIN SCK SCLK PC7 SYNC PC6 LDAC SDO MISO DAC. 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 continuous or a gated clock. A continuous SCLK source can be used only if SYNC can be 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 AD5686R/ AD5685R/ AD5684R For example, to read back the DAC register for Channel A, the following sequence should be implemented: SCLK SYNC 1. LDAC SDO 2. SDIN AD5686R/ AD5685R/ AD5684R SCLK SYNC LDAC *ADDITIONAL PINS OMITTED FOR CLARITY. 10485-057 SDO Figure 54. Daisy-Chaining the AD5686R/AD5685R/AD5684R The SCLK pin 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 input 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 this line to the SDIN input on the next DAC in the chain, a daisy-chain interface is constructed. Each DAC in the system requires 24 clock pulses. Therefore, the total number of clock cycles must equal 24 × N, where N is the total number of devices that are updated. If SYNC is taken high at a clock that is not a multiple of 24, it is considered a valid frame and invalid data may be loaded to the Rev. 0 | Page 23 of 32 Write 0x900000 to the AD5686R/AD5685R/AD5684R input register. This configures the part for read mode with the DAC register of Channel A selected. Note that all data bits, DB15 to DB0, are don’t care bits. Follow this with a second write, a NOP condition, 0x000000. During this write, the data from the register is clocked out on the SDO line. DB23 to DB20 contain undefined data, and the last 16 bits contain the DB19 to DB4 DAC register contents. AD5686R/AD5685R/AD5684R Data Sheet POWER-DOWN OPERATION output stage is also internally switched from the output of the amplifier to a resistor network of known values. This has the advantage that the output impedance of the part is known while the part is in power-down mode. There are three different power-down options. The output is connected internally to GND through either a 1 kΩ or a 100 kΩ resistor, or it is left open-circuited (three-state). The output stage is illustrated in Figure 55. The AD5686R/AD5685R/AD5684R contain three separate power-down modes. Command 0100 is designated for the powerdown function (see Table 7). These power-down modes are software-programmable by setting eight bits, Bit DB7 to Bit DB0, in the input shift register. There are two bits associated with each DAC channel. Table 10 shows how the state of the two bits corresponds to the mode of operation of the device. Table 10. Modes of Operation PDx1 0 PDx0 0 0 1 1 1 0 1 DAC AMPLIFIER POWER-DOWN CIRCUITRY VOUTX RESISTOR NETWORK 10485-058 Operating Mode Normal Operation Power-Down Modes 1 kΩ to GND 100 kΩ to GND Three-State Figure 55. Output Stage During Power-Down Any or all DACs (DAC A to DAC D) can be powered down to the selected mode by setting the corresponding bits. See Table 11 for the contents of the input shift register during the power-down/power-up operation. The bias generator, output amplifier, resistor string, and other associated linear circuitry are shut down when the power-down mode is activated. However, the contents of the DAC register are unaffected when in power-down. The DAC register can be updated while the device is in power-down mode. The time required to exit power-down is typically 4.5 µs for VDD = 5 V. When both Bit PDx1 and Bit PDx0 (where x is the channel selected) in the input shift register are set to 0, the parts work normally with its normal power consumption of 4 mA at 5 V. However, for the three power-down modes, the supply current falls to 4 μA at 5 V. Not only does the supply current fall, but the To reduce the current consumption further, the on-chip reference can be powered off. See the Internal Reference Setup section. Table 11. 24-Bit Input Shift Register Contents of Power-Down/Power-Up Operation 1 DB23 0 DB22 1 DB21 0 DB20 0 Command bits (C3 to C0) 1 DB19 to DB16 X Address bits Don’t care DB15 to DB8 X DB7 PDD1 DB6 PDD0 Power-Down Select DAC D X = don’t care. Rev. 0 | Page 24 of 32 DB5 PDC1 DB4 PDC0 Power-Down Select DAC C DB3 PDB1 DB2 PDB0 Power-Down Select DAC B DB1 PDA1 DB0 (LSB) PDA0 Power-Down Select DAC A Data Sheet AD5686R/AD5685R/AD5684R LOAD DAC (HARDWARE LDAC PIN) LDAC MASK REGISTER The AD5686R/AD5685R/AD5684R DACs have double buffered interfaces consisting of two banks of registers: input registers and DAC registers. The user can write to any combination of the input registers. Updates to the DAC register are controlled by the LDAC pin. Command 0101 is reserved for this software LDAC function. Address bits are ignored. Writing to the DAC, using Command 0101, loads the 4-bit LDAC register (DB3 to DB0). The default for each channel is 0; that is, the LDAC pin works normally. Setting the bits to 1 forces this DAC channel to ignore transitions on the LDAC pin, regardless of the state of the hardware LDAC pin. This flexibility is useful in applications where the user wishes to select which channels respond to the LDAC pin. OUTPUT AMPLIFIER VREF 16-/14-/12-BIT DAC LDAC DAC REGISTER VOUTX Table 12. LDAC Overwrite Definition Load LDAC Register LDAC Bits (DB3 to DB0) 0 1 SCLK SYNC SDIN INTERFACE LOGIC SDO LDAC Pin LDAC Operation 1 or 0 X1 Determined by the LDAC pin. DAC channels update and override the LDAC pin. DAC channels see LDAC as 1. 10485-059 INPUT REGISTER 1 Figure 56. Simplified Diagram of Input Loading Circuitry for a Single DAC X = don’t care. The LDAC register gives the user extra flexibility and control over the hardware LDAC pin (see Table 12). Setting the LDAC bits (DB0 to DB3) to 0 for a DAC channel means that this channel’s update is controlled by the hardware LDAC pin. Instantaneous DAC Updating (LDAC Held Low) LDAC is held low while data is clocked into the input register using Command 0001. Both the addressed input register and the DAC register are updated on the rising edge of SYNC and the output begins to change (see Table 13). Deferred DAC Updating (LDAC is Pulsed Low) LDAC is held high while data is clocked into the input register using Command 0001. All DAC outputs are asynchronously updated by taking LDAC low after SYNC has been taken high. The update now occurs on the falling edge of LDAC. Table 13. Write Commands and LDAC Pin Truth Table1 Commands 0001 Description Write to Input Register n (dependent on LDAC) 0010 Update DAC Register n with contents of Input Register n 0011 Write to and update DAC Channel n Hardware LDAC Pin State VLOGIC GND2 VLOGIC Input Register Contents Data update Data update No change GND No change VLOGIC GND Data update Data update DAC Register Contents No change (no update) Data update Updated with input register contents Updated with input register contents Data update Data update A high to low hardware LDAC pin transition always updates the contents of the contents of the DAC register with the contents of the input register on channels that are not masked (blocked) by the LDAC mask register. 2 When LDAC is permanently tied low, the LDAC mask bits are ignored. 1 Rev. 0 | Page 25 of 32 AD5686R/AD5685R/AD5684R Data Sheet HARDWARE RESET (RESET) SOLDER HEAT REFLOW RESET is an active low reset that allows the outputs to be cleared to either zero scale or midscale. The clear code value is user selectable via the RESET select pin. It is necessary to keep RESET low for a minimum amount of time to complete the operation (see Figure 2). When the RESET signal is returned high, the output remains at the cleared value until a new value is programmed. The outputs cannot be updated with a new value while the RESET pin is low. There is also a software executable reset function that resets the DAC to the power-on reset code. Command 0110 is designated for this software reset function (see Table 7). Any events on LDAC or RESET during power-on reset are ignored. As with all IC reference voltage circuits, the reference value experiences a shift induced by the soldering process. Analog Devices, Inc., performs a reliability test called precondition to mimic the effect of soldering a device to a board. The output voltage specification quoted previously includes the effect of this reliability test. Figure 57 shows the effect of solder heat reflow (SHR) as measured through the reliability test (precondition). RESET SELECT PIN (RSTSEL) 60 POSTSOLDER HEAT REFLOW 50 PRESOLDER HEAT REFLOW 30 20 10 0 2.498 2.499 INTERNAL REFERENCE SETUP The on-chip reference is on at power-up by default. To reduce the supply current, this reference can be turned off by setting software programmable bit, DB0, in the control register. Table 14 shows how the state of the bit corresponds to the mode of operation. Command 0111 is reserved for setting up the internal reference (see Figure 9). Table 14 shows how the state of the bits in the input shift register corresponds to the mode of operation of the device during internal reference setup. 2.502 LONG-TERM TEMPERATURE DRIFT Figure 58 shows the change in VREF value after 1000 hours in life test at 150°C. 60 0 HOUR 168 HOURS 500 HOURS 1000 HOURS 50 40 HITS 30 20 10 0 2.498 2.499 2.500 2.501 2.502 VREF (V) Figure 58. Reference Drift Through to 1000 Hours Rev. 0 | Page 26 of 32 10485-061 Action Reference on (default) Reference off 2.501 Figure 57. SHR Reference Voltage Shift Table 14. Reference Setup Register Internal Reference Setup Register (DB0) 0 1 2.500 VREF (V) 10485-060 The AD5686R/AD5685R/AD5684R contain a power-on reset circuit that controls the output voltage during power-up. By connecting the RSTSEL pin low, the output powers up to zero scale. Note that this is outside the linear region of the DAC; by connecting the RSTSEL pin high, VOUT powers up to midscale. The output remains powered up at this level until a valid write sequence is made to the DAC. HITS 40 Data Sheet AD5686R/AD5685R/AD5684R THERMAL HYSTERESIS 9 Thermal hysteresis is the voltage difference induced on the reference voltage by sweeping the temperature from ambient to cold, to hot, and then back to ambient. 8 7 6 5 4 3 2 1 0 –200 –150 –100 –50 0 DISTORTION (ppm) Figure 59. Thermal Hysteresis Table 15. 24-Bit Input Shift Register Contents for Internal Reference Setup Command1 DB23 (MSB) DB22 DB21 DB20 0 1 1 1 Command bits (C3 to C0) 1 DB19 X DB18 DB17 DB16 X X X Address bits (A2 to A0) X = don’t care. Rev. 0 | Page 27 of 32 DB15 to DB1 X Don’t care DB0 (LSB) 1/0 Reference setup register 50 10485-062 HITS Thermal hysteresis data is shown in Figure 59. It is measured by sweeping the temperature from ambient to −40°C, then to +105°C, and returning to ambient. The VREF delta is then measured between the two ambient measurements and shown in blue in Figure 59. The same temperature sweep and measurements were immediately repeated and the results are shown in red in Figure 59. FIRST TEMPERATURE SWEEP SUBSEQUENT TEMPERATURE SWEEPS AD5686R/AD5685R/AD5684R Data Sheet APPLICATIONS INFORMATION MICROPROCESSOR INTERFACING LAYOUT GUIDELINES Microprocessor interfacing to the AD5686R/AD5685R/ AD5684R is via a serial bus that uses a standard protocol that is compatible with DSP processors and microcontrollers. The communications channel requires a 3- or 4-wire interface consisting of a clock signal, a data signal, and a synchronization signal. The devices require a 24-bit data-word with data valid on the rising edge of SYNC. In any circuit where accuracy is important, careful consideration of the power supply and ground return layout helps to ensure the rated performance. The PCB on which the AD5686R/ AD5685R/AD5684R are mounted should be designed so that the AD5686R/AD5685R/AD5684R lie on the analog plane. AD5686R/AD5685R/AD5684R TO ADSP-BF531 INTERFACE The SPI interface of the AD5686R/AD5685R/AD5684R is designed to be easily connected to industry-standard DSPs and microcontrollers. Figure 60 shows the AD5686R/AD5685R/ AD5684R connected to the Analog Devices Blackfin® DSP. The Blackfin has an integrated SPI port that can be connected directly to the SPI pins of the AD5686R/AD5685R/AD5684R. AD5686R/ AD5685R/ AD5684R SYNC SCLK SDIN LDAC RESET 10485-164 PF9 PF8 In systems where there are many devices on one board, it is often useful to provide some heat sinking capability to allow the power to dissipate easily. The AD5686R/AD5685R/AD5684R have an exposed paddle beneath the device. Connect this paddle to the GND supply for the part. For optimum performance, use special considerations to design the motherboard and to mount the package. For enhanced thermal, electrical, and board level performance, solder the exposed paddle on the bottom of the package to the corresponding thermal land paddle on the PCB. Design thermal vias into the PCB land paddle area to further improve heat dissipation. ADSP-BF531 SPISELx SCK MOSI The AD5686R/AD5685R/AD5684R 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 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, which provide a low impedance path to ground at high frequencies to handle transient currents due to internal logic switching. Figure 60. ADSP-BF531 Interface AD5686R/AD5685R/AD5684R TO SPORT INTERFACE The Analog Devices ADSP-BF527 has one SPORT serial port. Figure 61 shows how one SPORT interface can be used to control the AD5686R/AD5685R/AD5684R. The GND plane on the device can be increased (as shown in Figure 62) to provide a natural heat sinking effect. AD5686R/ AD5685R/ AD5684R AD5686R/ AD5685R/ AD5684R ADSP-BF527 GND PLANE SYNC SCLK SDIN LDAC RESET 10485-165 BOARD GPIO0 GPIO1 Figure 62. Paddle Connection to Board Figure 61. SPORT Interface Rev. 0 | Page 28 of 32 10485-166 SPORT_TFS SPORT_TSCK SPORT_DTO Data Sheet AD5686R/AD5685R/AD5684R CONTROLLER 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. iCoupler® products from Analog Devices provide voltage isolation in excess of 2.5 kV. The serial loading structure of the AD5686R/AD5685R/AD5684R makes the part ideal for isolated interfaces because the number of interface lines is kept to a minimum. Figure 63 shows a 4-channel isolated interface to the AD5686R/AD5685R/AD5684R using an ADuM1400. For further information, visit http://www.analog.com/icouplers. SERIAL CLOCK IN SERIAL DATA OUT ADuM14001 VOA VIA ENCODE DECODE ENCODE DECODE ENCODE DECODE ENCODE DECODE VIB VOB VIC SYNC OUT LOAD DAC OUT 1 VOC VOD VID ADDITIONAL PINS OMITTED FOR CLARITY. Rev. 0 | Page 29 of 32 Figure 63. Isolated Interface TO SCLK TO SDIN TO SYNC TO LDAC 10485-167 GALVANICALLY ISOLATED INTERFACE AD5686R/AD5685R/AD5684R Data Sheet OUTLINE DIMENSIONS 3.10 3.00 SQ 2.90 0.50 BSC 13 PIN 1 INDICATOR 16 1 12 EXPOSED PAD 1.75 1.60 SQ 1.45 9 TOP VIEW 0.80 0.75 0.70 4 5 8 0.50 0.40 0.30 FOR PROPER CONNECTION OF THE EXPOSED PAD, REFER TO THE PIN CONFIGURATION AND FUNCTION DESCRIPTIONS SECTION OF THIS DATA SHEET. 0.05 MAX 0.02 NOM COPLANARITY 0.08 0.20 REF SEATING PLANE 0.25 MIN BOTTOM VIEW 08-16-2010-E PIN 1 INDICATOR 0.30 0.23 0.18 COMPLIANT TO JEDEC STANDARDS MO-220-WEED-6. Figure 64. 16-Lead Lead Frame Chip Scale Package [LFCSP_WQ] 3 mm × 3 mm Body, Very Very Thin Quad (CP-16-22) Dimensions shown in millimeters 5.10 5.00 4.90 16 9 4.50 4.40 4.30 6.40 BSC 1 8 PIN 1 1.20 MAX 0.15 0.05 0.20 0.09 0.65 BSC 0.30 0.19 COPLANARITY 0.10 SEATING PLANE 8° 0° COMPLIANT TO JEDEC STANDARDS MO-153-AB Figure 65. 16-Lead Thin Shrink Small Outline Package [TSSOP] (RU-16) Dimensions shown in millimeters Rev. 0 | Page 30 of 32 0.75 0.60 0.45 Data Sheet AD5686R/AD5685R/AD5684R ORDERING GUIDE Model 1 AD5686RACPZ-RL7 AD5686RBCPZ-RL7 AD5686RARUZ AD5686RARUZ-RL7 AD5686RBRUZ AD5686RBRUZ-RL7 AD5685RBCPZ-RL7 AD5685RARUZ AD5685RARUZ-RL7 AD5685RBRUZ AD5685RBRUZ-RL7 AD5684RBCPZ-RL7 AD5684RARUZ AD5684RARUZ-RL7 AD5684RBRUZ AD5684RBRUZ-RL7 EVAL-AD5686RSDZ Resolution 16 Bits 16 Bits 16 Bits 16 Bits 16 Bits 16 Bits 14 Bits 14 Bits 14 Bits 14 Bits 14 Bits 12 Bits 12 Bits 12 Bits 12 Bits 12 Bits Temperature Range −40°C to +105°C −40°C to +105°C −40°C to +105°C −40°C to +105°C −40°C to +105°C −40°C to +105°C −40°C to +105°C −40°C to +105°C −40°C to +105°C −40°C to +105°C −40°C to +105°C −40°C to +105°C −40°C to +105°C −40°C to +105°C −40°C to +105°C −40°C to +105°C Accuracy ±8 LSB INL ±2 LSB INL ±8 LSB INL ±8 LSB INL ±2 LSB INL ±2 LSB INL ±1 LSB INL ±4 LSB INL ±4 LSB INL ±1 LSB INL ±1 LSB INL ±1 LSB INL ±2 LSB INL ±2 LSB INL ±1 LSB INL ±1 LSB INL Reference Tempco (ppm/°C) ±5 (typ) ±5 (max) ±5 (typ) ±5 (typ) ±5 (max) ±5 (max) ±5 (max) ±5 (typ) ±5 (typ) ±5 (max) ±5 (max) ±5 (max) ±5 (typ) ±5 (typ) ±5 (max) ±5 (max) EVAL-AD5684RSDZ 1 Z = RoHS Compliant Part. Rev. 0 | Page 31 of 32 Package Description 16-Lead LFCSP_WQ 16-Lead LFCSP_WQ 16-Lead TSSOP 16-Lead TSSOP 16-Lead TSSOP 16-Lead TSSOP 16-Lead LFCSP_WQ 16-Lead TSSOP 16-Lead TSSOP 16-Lead TSSOP 16-Lead TSSOP 16-Lead LFCSP_WQ 16-Lead TSSOP 16-Lead TSSOP 16-Lead TSSOP 16-Lead TSSOP AD5686R TSSOP Evaluation Board AD5684R TSSOP Evaluation Board Package Option CP-16-22 CP-16-22 RU-16 RU-16 RU-16 RU-16 CP-16-22 RU-16 RU-16 RU-16 RU-16 CP-16-22 RU-16 RU-16 RU-16 RU-16 Branding DJM DJN DJK DJG AD5686R/AD5685R/AD5684R Data Sheet NOTES ©2012 Analog Devices, Inc. All rights reserved. Trademarks and registered trademarks are the property of their respective owners. D10485-0-4/12(0) Rev. 0 | Page 32 of 32