ANALOG DEVICES AD5666

Quad, 16-Bit DAC with 5 ppm/°C On-Chip Reference in 14-Lead TSSOP AD5666 FEATURES FUNCTIONAL BLOCK DIAGRAM V /V V REFIN REFOUT DD Low power quad 16-bit DAC AD5666 1.25V/2.5V 14-lead TSSOP REF LDAC BUFFER On-chip 1.25 V/2.5 V, 5 ppm/°C reference INPUT DAC STRING V A OUT REGISTER REGISTER DAC A SCLK Power down to 400 nA @ 5 V, 200 nA @ 3 V BUFFER INPUT DAC STRING V B OUT REGISTER REGISTER DAC B INTERFACE 2.7 V to 5.5 V power supply SYNC LOGIC BUFFER INPUT DAC STRING V C OUT Guaranteed monotonic by design REGISTER REGISTER DAC C DIN BUFFER DAC STRING Power-on reset to zero scale or midscale INPUT V D OUT REGISTER REGISTER DAC D SDO 3 power-down functions POWER-ON POWER-DOWN LOGIC RESET Hardware LDAC with LDAC override function POR GND LDAC CLR CLR function to programmable code Figure 1. SDO daisy-chaining option Rail-to-rail operation APPLICATIONS Process control Data acquisition systems Portable battery-powered instruments Digital gain and offset adjustment Programmable voltage and current sources Programmable attenuators GENERAL DESCRIPTION The AD5666 is a low power, quad, 16-bit, buffered voltage- The outputs of all DACs can be updated simultaneously using output DAC. The part operates from a single 2.7 V to 5.5 V the LDAC function, with the added functionality of user-select- supply and is guaranteed monotonic by design. able DAC channels to simultaneously update. There is also an asynchronous that clears all DACs to a software-selectable CLR The AD5666 has an on-chip reference with an internal gain of 2. code—0 V, midscale, or full scale. The AD5666-1 has a 1.25 V 5 ppm/°C reference, giving a full-scale output of 2.5 V; the AD5666-2 has a 2.5 V 5 ppm/°C reference, The AD5666 utilizes a versatile 3-wire serial interface that operates giving a full-scale output of 5 V. The on-board reference is off at at clock rates of up to 50 MHz and is compatible with standard power-up, allowing the use of an external reference. The internal SPI®, QSPI™, MICROWIRE™, and DSP interface standards. The reference is turned on by writing to the DAC. on-chip precision output amplifier enables rail-to-rail output swing. The part incorporates a power-on reset circuit that ensures that the DAC output powers up to 0 V (POR pin low) or to midscale PRODUCT HIGHLIGHTS (POR pin high) and remains powered up at this level until a valid 1. Quad, 16-bit DAC. write takes place. The part contains a power-down feature that 2. On-chip 1.25 V/2.5 V, 5 ppm/°C reference. reduces the current consumption of the device to 400 nA at 5 V 3. Available in 14-lead TSSOP. and provides software-selectable output loads while in power-down 4. Selectable power-on reset to 0 V or midscale. mode for any or all DAC channels. 5. Power-down capability. When powered down, the DAC typically consumes 200 nA at 3 V and 400 nA at 5 V. Rev. D 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 One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A. rights of third parties that may result from its use. Specifications subject to change without notice. No Tel: 781.329.4700 www.analog.com license is granted by implication or otherwise under any patent or patent rights of Analog Devices. Fax: 781.461.3113 ©2005–2010 Analog Devices, Inc. All rights reserved. Trademarks and registered trademarks are the property of their respective owners. 05298-001 AD5666 TABLE OF CONTENTS Features .............................................................................................. 1  Resistor String ............................................................................. 20  Applications ....................................................................................... 1  Internal Reference ...................................................................... 20  Functional Block Diagram .............................................................. 1  Output Amplifier ........................................................................ 21  General Description ......................................................................... 1  Serial Interface ............................................................................ 21  Product Highlights ........................................................................... 1  Input Shift Register .................................................................... 22  Revision History ............................................................................... 2  Interrupt .......................................................................... 22  SYNC Specif ica t ions ..................................................................................... 3  Daisy-Chaining ........................................................................... 23  AC Characteristics ........................................................................ 7  Internal Reference Register ....................................................... 23  Timing Characteristics ................................................................ 8  Power-On Reset .......................................................................... 23  Absolute Maximum Ratings .......................................................... 10  Power-Down Modes .................................................................. 23  ESD Caution ................................................................................ 10  Clear Code Register ................................................................... 25  Pin Configuration and Function Descriptions ........................... 11  Function .......................................................................... 25  LDAC Typical Performance Characteristics ........................................... 12  Power Supply Bypassing and Grounding ................................ 25  Terminology .................................................................................... 18  Outline Dimensions ....................................................................... 27  Theory of Operation ...................................................................... 20  Ordering Guide .......................................................................... 27  D/A Section ................................................................................. 20  REVISION HISTORY 6/10—Rev. C to Rev. D Changes to Figure 19 and Figure 20 Captions ............................ 14 10/09—Rev. B to Rev. C Changes to Table 7 .......................................................................... 21 2/09—Rev. A to Rev. B Changes to Reference Current Parameter, Table 1 ....................... 3 Changes to Reference Current Parameter, Table 2 ....................... 5 Updated Outline Dimensions ....................................................... 27 11/05—Rev. 0 to Rev. A Change to General Description ...................................................... 1 Change to Specifications .................................................................. 3 10/05—Revision 0: Initial Version Rev. D | Page 2 of 28 AD5666 SPECIFICATIONS VDD = 4.5 V to 5.5 V, RL = 2 kΩ to GND, CL = 200 pF to GND, VREFIN = VDD. All specifications TMIN to TMAX, unless otherwise noted. Table 1. 1 1 A Grade B Grade Parameter Min Typ Max Min Typ Max Unit Conditions/Comments 2 STATIC PERFORMANCE Resolution 16 16 Bits Relative Accuracy ±32 ±16 LSB See Figure 6 Differential Nonlinearity ±1 ±1 LSB Guaranteed monotonic by design (see Figure 7) Zero-Code Error 1 9 1 9 mV All 0s loaded to DAC register (see Figure 13) Zero-Code Error Drift ±2 ±2 μV/°C Full-Scale Error −0.2 −1 −0.2 −1 % FSR All 1s loaded to DAC register (see Figure 12) Gain Error ±1 ±1 % FSR Gain Temperature Coefficient ±2.5 ±2.5 ppm Of FSR/°C Offset Error ±1 ±9 ±1 ±9 mV DC Power Supply Rejection –80 –80 dB VDD ± 10% Ratio DC Crosstalk 10 10 μV Due to full-scale output change, (External Reference) R = 2 kΩ to GND or V L DD 5 5 μV/mA Due to load current change 10 10 μV Due to powering down (per channel) DC Crosstalk 25 25 μV Due to full-scale output change, (Internal Reference) RL = 2 kΩ to GND or VDD 10 10 μV/mA Due to load current change 3 OUTPUT CHARACTERISTICS Output Voltage Range 0 VDD 0 VDD V Capacitive Load Stability 2 2 nF R = ∞ L 10 10 nF R = 2 kΩ L DC Output Impedance 0.5 0.5 Ω Short-Circuit Current 30 30 mA VDD = 5 V Power-Up Time 4 4 μs Coming out of power-down mode VDD = 5 V REFERENCE INPUTS Reference Input Voltage VDD VDD V Reference Current 20 55 20 55 μA VREF = VDD = 5.5 V Reference Input Range 0 VDD 0 VDD V Reference Input Impedance 14.6 14.6 kΩ Per DAC channel REFERENCE OUTPUT Output Voltage 2.495 2.505 2.495 2.505 V At ambient 3 Reference TC ±5 ±10 ±5 ±10 ppm/°C Reference Output 7.5 7.5 kΩ Impedance 3 LOGIC INPUTS Input Current ±3 ±3 μA All digital inputs Input Low Voltage, VINL 0.8 0.8 V VDD = 5 V Input High Voltage, VINH 2 2 V VDD = 5 V Pin Capacitance 3 3 pF Rev. D | Page 3 of 28 AD5666 1 1 A Grade B Grade Parameter Min Typ Max Min Typ Max Unit Conditions/Comments 3 LOGIC OUTPUTS (SDO) Output Low Voltage, V 0.4 0.4 V I = 2 mA OL SINK Output High Voltage, V V − V − I = 2 mA OH DD DD SOURCE 1 1 High Impedance Leakage ±0.25 ±0.25 μA Current High Impedance Output 2 2 pF Capacitance POWER REQUIREMENTS VDD 4.5 5.5 4.5 5.5 V All digital inputs at 0 or V , DD DAC active, excludes load current 4 I (Normal Mode) V = V and V = GND DD IH DD IL VDD = 4.5 V to 5.5 V 0.7 0.9 0.7 0.9 mA Internal reference off VDD = 4.5 V to 5.5 V 1.3 1.6 1.3 1.6 mA Internal reference on 5 IDD (All Power-Down Modes) V = 4.5 V to 5.5 V 0.4 1 0.4 1 μA V = V and V = GND DD IH DD IL 1 Temperature range is −40°C to +105°C, typical at 25°C. 2 Linearity calculated using a reduced code range of 512 to 65,024. Output unloaded. 3 Guaranteed by design and characterization; not production tested. 4 Interface inactive. All DACs active. DAC outputs unloaded. 5 All four DACs powered down. Rev. D | Page 4 of 28 AD5666 V = 2.7 V to 3.6 V, R = 2 kΩ to GND, C = 200 pF to GND, V = V . All specifications T to T , unless otherwise noted. DD L L REFIN DD MIN MAX Table 2. 1 1 A Grade B Grade Parameter Min Typ Max Min Typ Max Unit Conditions/Comments 2 STATIC PERFORMANCE Resolution 16 16 Bits Relative Accuracy ±32 ±16 LSB See Figure 5 Differential Nonlinearity ±1 ±1 LSB Guaranteed monotonic by design (see Figure 6) Zero-Code Error 1 9 1 9 mV All 0s loaded to DAC register (see Figure 13) Zero-Code Error Drift ±2 ±2 μV/°C Full-Scale Error −0.2 −1 −0.2 −1 % FSR All 1s loaded to DAC register (see Figure 12) Gain Error ±1 ±1 % FSR Gain Temperature ±2.5 ±2.5 ppm Of FSR/°C Coefficient Offset Error ±1 ±9 ±1 ±9 mV DC Power Supply Rejection –80 –80 dB V ± 10% DD Ratio DC Crosstalk 10 10 μV Due to full-scale output change, (External Reference) RL = 2 kΩ to GND or VDD 5 5 μV/mA Due to load current change 10 10 μV Due to powering down (per channel) DC Crosstalk 25 25 μV Due to full-scale output change, (Internal Reference) RL = 2 kΩ to GND or VDD 10 10 μV/mA Due to load current change 3 OUTPUT CHARACTERISTICS Output Voltage Range 0 VDD 0 VDD V Capacitive Load Stability 2 2 nF RL = ∞ 10 10 nF RL = 2 kΩ DC Output Impedance 0.5 0.5 Ω Short-Circuit Current 30 30 mA V = 3 V coming out of power-down mode DD Power-Up Time 4 4 μs Coming out of power-down V = 3 V DD REFERENCE INPUTS Reference Input Voltage V V V DD DD Reference Current 40 55 40 55 μA VREF = VDD = 3.6 V Reference Input Range 0 VDD 0 VDD Reference Input Impedance 14.6 14.6 kΩ Per DAC channel REFERENCE OUTPUT Output Voltage 1.247 1.253 1.247 1.253 V At ambient 3 Reference TC ±5 ±15 ±5 ±15 ppm/°C Reference Output 7.5 7.5 kΩ Impedance 3 LOGIC INPUTS Input Current ±3 ±3 μA Input Low Voltage, V 0.8 0.8 V V = 3 V INL DD Input High Voltage, VINH 2 2 V VDD = 3 V Pin Capacitance 3 3 pF 3 LOGIC OUTPUTS (SDO) Output Low Voltage, VOL 0.4 0.4 V ISINK = 2 mA Output High Voltage, VOH VDD − VDD − ISOURCE = 2 mA 0.5 0.5 High Impedance Leakage ±0.25 ±0.25 μA Current High Impedance Leakage 2 2 pF Rev. D | Page 5 of 28 AD5666 1 1 A Grade B Grade Parameter Min Typ Max Min Typ Max Unit Conditions/Comments Current POWER REQUIREMENTS VDD 2.7 3.6 2.7 3.6 V All digital inputs at 0 or VDD, DAC active, excludes load current 4 I (Normal Mode) V = V and V = GND DD IH DD IL V = 2.7 V to 3.6 V 0.65 0.85 0.65 0.85 mA Internal reference off DD V = 2.7 V to 3.6 V 1.3 1.5 1.3 1.5 mA Internal reference on DD 5 IDD (All Power-Down Modes) VDD = 2.7 V to 3.6 V 0.2 1 0.2 1 μA VIH = VDD and VIL = GND 1 Temperature range is −40°C to +105°C, typical at 25°C. 2 Linearity calculated using a reduced code range of 512 to 65,024. Output unloaded. 3 Guaranteed by design and characterization; not production tested. 4 Interface inactive. All DACs active. DAC outputs unloaded. 5 All four DACs powered down. Rev. D | Page 6 of 28 AD5666 AC CHARACTERISTICS VDD =2.7V to 5.5 V, RL = 2 kΩ to GND, CL = 200 pF to GND, VREFIN = VDD. All specifications TMIN to TMAX, unless otherwise noted. Table 3. 1, 2 3 Parameter Min Typ Max Unit Conditions/Comments Output Voltage Settling Time 6 10 μs ¼ to ¾ scale settling to ±2 LSB Slew Rate 1.5 V/μs Digital-to-Analog Glitch Impulse 4 nV-s 1 LSB change around major carry (see Figure 29) Reference Feedthrough −90 dB VREF = 2 V ± 0.1 V p-p, frequency = 10 Hz to 20 MHz SDO Feedthrough 3 nV-s Daisy-chain mode; SDO load is 10 pF Digital Feedthrough 0.1 nV-s Digital Crosstalk 0.5 nV-s Analog Crosstalk 2.5 nV-s DAC-to-DAC Crosstalk 3 nV-s Multiplying Bandwidth 340 kHz V = 2 V ± 0.2 V p-p REF Total Harmonic Distortion −80 dB V = 2 V ± 0.1 V p-p, frequency = 10 kHz REF Output Noise Spectral Density 120 nV/√Hz DAC code = 0x8400, 1 kHz 100 nV/√Hz DAC code = 0x8400, 10 kHz Output Noise 15 μV p-p 0.1 Hz to 10 Hz 1 Guaranteed by design and characterization; not production tested. 2 See the Terminology section. 3 Temperature range is −40°C to + 105°C, typical at 25°C. Rev. D | Page 7 of 28 AD5666 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 3 and Figure 5. VDD = 2.7 V to 5.5 V. All specifications TMIN to TMAX, unless otherwise noted. Table 4. Limit at TMIN, TMAX Parameter V = 2.7 V to 5.5 V Unit Conditions/Comments DD 1 t1 20 ns min SCLK cycle time t 8 ns min SCLK high time 2 t 8 ns min SCLK low time 3 t 13 ns min to SCLK falling edge set-up time 4 SYNC t5 4 ns min Data set-up time t6 4 ns min Data hold time t7 0 ns min SCLK falling edge to SYNC rising edge t 15 ns min Minimum SYNC high time 8 t 13 ns min SYNC rising edge to SCLK fall ignore 9 t10 0 ns min SCLK falling edge to SYNC fall ignore t11 10 ns min LDAC pulse width low t12 15 ns min SCLK falling edge to LDAC rising edge t 5 ns min CLR pulse width low 13 t 0 ns min SCLK falling edge to LDAC falling edge 14 t 300 ns typ CLR pulse activation time 15 2, 3 t16 22 ns max SCLK rising edge to SDO valid 3 t17 5 ns min SCLK falling edge to SYNC rising edge 3 t18 8 ns min SYNC rising edge to SCLK rising edge 3 t 0 ns min SYNC rising edge to LDAC falling edge 19 1 Maximum SCLK frequency is 50 MHz at V = 2.7 V to 5.5 V. Guaranteed by design and characterization; not production tested. DD 2 Measured with the load circuit of Figure 16. t16 determines the maximum SCLK frequency in daisy-chain mode. 3 Daisy-chain mode only. 2mA I OL TO OUTPUT V (MIN) OH PIN C L 50pF 2mA I OH Figure 2. Load Circuit for Digital Output (SDO) Timing Specifications Rev. D | Page 8 of 28 05298-002 AD5666 t 10 t 1 t 9 SCLK t 2 t 8 t t 7 t 3 4 SYNC t 6 t 5 DIN DB31 DB0 t 11 t 14 1 LDAC t 12 2 LDAC t 13 CLR 1 ASYNCHRONOUS LDAC UPDATE MODE 2 SYNCHRONOUS LDAC UPDATE MODE Figure 3. Serial Write Operation t 1 SCLK 32 64 t t t 18 3 2 t t 7 4 t 17 SYNC t 8 t 9 DB0 DIN DB31 DB0 DB31 INPUT WORD FOR DAC N INPUT WORD FOR DAC N + 1 t 16 SDO DB31 DB0 UNDEFINED INPUT WORD FOR DAC N t 19 t 11 LDAC Figure 4. Daisy-Chain Timing Diagram Rev. D | Page 9 of 28 05298-003 05298-004 AD5666 ABSOLUTE MAXIMUM RATINGS TA = 25°C, unless otherwise noted. Table 5. Stresses above those listed under Absolute Maximum Ratings Parameter Rating may cause permanent damage to the device. This is a stress V to GND −0.3 V to +7 V DD rating only; functional operation of the device at these or any Digital Input Voltage to GND −0.3 V to V + 0.3 V DD other conditions above those indicated in the operational VOUT to GND −0.3 V to VDD + 0.3 V section of this specification is not implied. Exposure to absolute VREFIN/VREFOUT to GND −0.3 V to VDD + 0.3 V maximum rating conditions for extended periods may affect Operating Temperature Range device reliability. Industrial −40°C to +105°C Storage Temperature Range −65°C to +150°C Junction Temperature (T ) +150°C J MAX TSSOP Package Power Dissipation (TJ MAX − TA)/θJA θJA Thermal Impedance 150.4°C/W Reflow Soldering Peak Temperature SnPb 240°C Pb Free 260°C ESD CAUTION ESD (electrostatic discharge) sensitive device. Electrostatic charges as high as 4000 V readily accumulate on the human body and test equipment and can discharge without detection. Although this product features proprietary ESD protection circuitry, permanent damage may occur on devices subjected to high energy electrostatic discharges. Therefore, proper ESD precautions are recommended to avoid performance degradation or loss of functionality. Rev. D | Page 10 of 28 AD5666 PIN CONFIGURATION AND FUNCTION DESCRIPTIONS 1 LDAC 14 SCLK 2 13 SYNC DIN 3 12 V GND DD AD5666 V A 4 11 B V OUT TOP VIEW OUT (Not to Scale) V C 5 10 V D OUT OUT POR 6 9 CLR V /V 7 8 SDO REFIN REFOUT Figure 5. 14-Lead TSSOP (RU-14) Table 6. Pin Function Descriptions Pin No. Mnemonic Description 1 LDAC 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. Alternatively, this pin can be tied permanently low. 2 SYNC Active Low Control Input. This is the frame synchronization signal for the input data. When SYNC goes low, it powers on the SCLK and DIN buffers and enables the input shift register. Data is transferred in nd on the falling edges of the next 32 clocks. If SYNC is taken high before the 32 falling edge, the rising edge of SYNC acts as an interrupt and the write sequence is ignored by the device. 3 VDD 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. 4 V A Analog Output Voltage from DAC A. The output amplifier has rail-to-rail operation. OUT 5 V C Analog Output Voltage from DAC C. The output amplifier has rail-to-rail operation. OUT 6 POR Power-on Reset Pin. Tying this pin to GND powers up the part to 0 V. Tying this pin to VDD powers up the part to midscale. 7 VREFIN/VREFOUT The AD5666 has a common pin for reference input and reference output. 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 input. 8 SDO Serial Data Output. Can be used for daisy-chaining a number of these devices together or for reading back the data in the shift register for diagnostic purposes. The serial data is transferred on the rising edge of SCLK and is valid on the falling edge of the clock. 9 CLR Asynchronous Clear Input. The CLR input is falling edge sensitive. When CLR is low, all LDAC pulses are ignored. When CLR is activated, the input register and the DAC register are updated with the data contained in the CLR code register—zero, midscale, or full scale. Default setting clears the output to 0 V. 10 VOUTD Analog Output Voltage from DAC D. The output amplifier has rail-to-rail operation. 11 VOUTB Analog Output Voltage from DAC B. The output amplifier has rail-to-rail operation. 12 GND Ground Reference Point for All Circuitry on the Part. 13 DIN Serial Data Input. This device has a 32-bit shift register. Data is clocked into the register on the falling edge of the serial clock input. 14 SCLK 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. Rev. D | Page 11 of 28 05298-005 AD5666 TYPICAL PERFORMANCE CHARACTERISTICS 1.0 V =5V DD 10 0.8 V =2.5V REFOUT V =V =5V DD REF T = 25°C A 8 T = 25°C A 0.6 6 0.4 4 0.2 2 0 0 –0.2 –2 –0.4 –4 –0.6 –6 –0.8 –8 –1.0 –10 0 5k 10k 15k 20k 25k 30k 35k 40k 45k 50k 55k 60k 65k CODE CODE Figure 9. DNL—AD5666-2 Figure 6. INL 10 V =3V DD 1.0 8 V =1.25V REFOUT V =V =5V DD REF T =25°C A 0.8 T = 25°C A 6 0.6 4 0.4 2 0.2 0 0 –2 –0.2 –4 –0.4 –6 –0.6 –8 –0.8 –10 –1.0 0 10k 20k 30k 40k 50k 60k CODE CODE Figure 7. DNL Figure 10. INL—AD5666-1 1.0 10 V =3V V =5V DD DD 0.8 V =1.25V 8 V =2.5V REFOUT REFOUT T =25°C T = 25°C A A 0.6 6 0.4 4 0.2 2 0 0 –0.2 –2 –0.4 –4 –0.6 –6 –0.8 –8 –1.0 –10 CODE CODE Figure 8. INL—AD5666-2 Figure 11. DNL—AD5666-1 Rev. D | Page 12 of 28 INL ERROR (LSB) DNL ERROR (LSB) INL ERROR (LSB) 0 5000 10000 15000 20000 25000 30000 35000 40000 45000 50000 55000 60000 65000 05298-008 05298-007 05298-006 DNL ERROR (LSB) DNL ERROR (LSB) INL ERROR (LSB) 0 0 0 5000 5000 5000 10000 10000 10000 15000 15000 15000 20000 20000 20000 25000 25000 25000 30000 30000 30000 35000 35000 35000 40000 40000 40000 45000 45000 45000 50000 50000 50000 55000 55000 55000 60000 60000 60000 65000 65000 65000 05298-011 05298-010 05298-009 AD5666 0 1.0 V = 5V T =25°C DD A –0.02 0.5 ZERO-SCALE ERROR –0.04 GAIN ERROR 0 –0.06 –0.08 –0.5 –0.10 –1.0 –0.12 –0.14 –1.5 FULL-SCALE ERROR –0.16 –2.0 OFFSET ERROR –0.18 –0.20 –2.5 –40 –20 0 20 40 60 80 100 2.7 3.2 3.7 4.2 4.7 5.2 V (V) TEMPERATURE (°C) DD Figure 12. Gain Error and Full-Scale Error vs. Temperature Figure 15. Zero-Scale Error and Offset Error vs. Supply Voltage 3.5 1.5 V =3.6V DD V =5.5V DD 1.0 3.0 ZERO-SCALE ERROR 0.5 2.5 0 2.0 –0.5 1.5 –1.0 1.0 –1.5 OFFSET ERROR 0.5 –2.0 0 –2.5 0.62 0.63 0.64 0.65 0.66 0.67 0.68 0.69 0.7 0.71 0.72 –40 –2008 20 40 600 100 I (mA) TEMPERATURE (°C) DD Figure 13. Zero-Scale Error and Offset Error vs. Temperature Figure 16. I Histogram with External Reference DD 1.0 2.5 V =3.6V DD V =5.5V DD 0.5 2.0 GAIN ERROR 0 1.5 FULL-SCALE ERROR –0.5 1.0 –1.0 0.5 –1.5 –2.0 0 2.7 3.2 3.7 4.2 4.7 5.2 1.26 1.28 1.30 1.32 1.34 1.36 1.38 I (mA) V (V) DD DD Figure 14. Gain Error and Full-Scale Error vs. Supply Voltage Figure 17. IDD Histogram with Internal Reference Rev. D | Page 13 of 28 ERROR (% FSR) ERROR (mV) ERROR (% FSR) 05298-031 05298-021 05298-030 FREQUENCY FREQUENCY ERROR (mV) 05298-029 05298-028 05298-045 AD5666 0.50 1.0 T =25°C V =V =5V DAC LOADED WITH DACLOADEDWITH A DD REF 0.40 FULL-SCALE ZERO-SCALE 0.9 SOURCING CURRENT SINKING CURRENT 0.30 0.8 0.7 0.20 V =3V 0.10 DD 0.6 V =V =3V V = 1.25V DD REF REFOUT 0.5 0 0.4 –0.10 0.3 –0.20 V =5V 0.2 –0.30 DD V =2.5V REFOUT 0.1 –0.40 –0.50 0 –10 –8 –6 –4 –2 0 2 461 8 0 512 10512 20512 30512 40512 50512 60512 CURRENT (mA) CODE Figure 18. Headroom at Rails vs. Source and Sink Figure 21. Supply Current vs. Code 6.00 1.0 V =5V DD FULL SCALE 0.9 V =2.5V REFOUT V =V =5.5V 5.00 DD REFIN T =25°C A 0.8 3/4 SCALE 4.00 0.7 0.6 3.00 V =V =3.6V MIDSCALE DD REFIN 0.5 2.00 0.4 1/4 SCALE 0.3 1.00 0.2 0 ZERO SCALE 0.1 –1.00 0 –30 –20 –10 0 10 20 30 –40 –20 0 20 40 60 80 100 CURRENT (mA) TEMPERATURE (°C) Figure 19. Source and Sink Current Capability with VDD = 5 V Figure 22. Supply Current vs. Temperature 1.0 4.00 T =25°C A V =3V DD 0.9 V = 1.25V REFOUT T =25°C A 0.8 3.00 FULL SCALE 0.7 3/4 SCALE 0.6 2.00 0.5 MIDSCALE 0.4 1.00 1/4 SCALE 0.3 0.2 0 ZERO SCALE 0.1 0 –1.00 –30 –20 –10 0 10 20 30 2.7 3.2 3.7 4.2 4.7 5.2 V (V) CURRENT (mA) DD Figure 20. Source and Sink Current Capability with VDD = 3 V Figure 23. Supply Current vs. Supply Voltage Rev. D | Page 14 of 28 V (V) V (V) ERROR VOLTAGE (V) OUT OUT 05298-013 05298-012 05298-019 I (mA) I (mA) I (mA) DD DD DD 05298-016 05298-015 05298-014 AD5666 4.0 T = 25°C A V =V =5V DD REF 3.5 T =25°C A 3.0 2.5 V DD 2.0 1 V =5V 1.5 DD 1.0 2 0.5 V OUT V =3V DD 0 0123 456 CH1 2.0V CH2 1.0V M100μs 125MS/s 8.0ns/pt V (V) A CH1 1.28V LOGIC Figure 24. Supply Current vs. Logic Input Voltage Figure 27. Power-On Reset to Midscale SYNC 1 SLCK 3 V =V =5V DD REF T =25°C A FULL-SCALE CODE CHANGE 0x0000 TO 0xFFFF OUTPUT LOADED WITH 2kΩ AND 200pF TO GND V OUT V = 909mV/DIV OUT V = 5V DD 1 2 CH1 5.0V CH2 500mV M400ns A CH1 1.4V CH3 5.0V TIME BASE = 4μs/DIV Figure 28. Exiting Power-Down to Midscale Figure 25. Full-Scale Settling Time 2.505 2.504 V =5V DD V =V =5V DD REF 2.503 V =2.5V REFOUT T =25°C A 2.502 T = 25°C A 2.501 4ns/SAMPLE NUMBER 2.500 GLITCH IMPULSE = 3.55nV-s 2.499 1 LSB CHANGE AROUND 2.498 MIDSCALE (0x8000 TO 0x7FFF) 2.497 2.496 2.495 2.494 V DD 2.493 1 2.492 2.491 2.490 MAX(C2)* 2.489 420.0mV 2.488 2 2.487 V OUT 2.486 2.485 0 64 128 192 256 320 384 448 512 CH1 2.0V CH2 500mV M100μs 125MS/s 8.0ns/pt A CH1 1.28V SAMPLE Figure 29. Digital-to-Analog Glitch Impulse Figure 26. Power-On Reset to 0 V Rev. D | Page 15 of 28 I (mA) DD 05298-020 05298-018 05298-017 V (V) OUT 05298-034 05298-033 05298-022 AD5666 2.5000 V =5V DD 2.4995 V =2.5V REFOUT T =25°C A 2.4990 DAC LOADED WITH MIDSCALE 2.4985 2.4980 2.4975 1 2.4970 2.4965 2.4960 V =5V DD V =2.5V REFOUT 2.4955 T = 25°C A 4ns/SAMPLE NUMBER 2.4950 0 64 128 192 256 320 384 448 512 SAMPLE 5s/DIV Figure 30. Analog Crosstalk Figure 33. 0.1 Hz to 10 Hz Output Noise Plot, Internal Reference 2.4900 V =3V DD 2.4895 V = 1.25V REFOUT T =25°C A 2.4890 DAC LOADED WITH MIDSCALE 2.4885 2.4880 1 2.4875 2.4870 2.4865 V =5V DD V =2.5V REFOUT 2.4860 T = 25°C A 4ns/SAMPLE NUMBER 2.4855 0 64 128 192 256 320 384 448 512 SAMPLE 4s/DIV Figure 31. DAC-to-DAC Crosstalk Figure 34. 0.1 Hz to 10 Hz Output Noise Plot, Internal Reference 800 T =25°C A MIDSCALE LOADED 700 V =V =5V DD REF T =25°C A 600 DAC LOADED WITH MIDSCALE 500 400 1 300 V =5V DD V =2.5V REFOUT 200 V =3V 100 DD V = 1.25V REFOUT 0 YAXIS = 2μV/DIV 100 1000 10000 100000 1000000 X AXIS = 4s/DIV FREQUENCY (Hz) Figure 32. 0.1 Hz to 10 Hz Output Noise Plot, External Reference Figure 35. Noise Spectral Density, Internal Reference Rev. D | Page 16 of 28 V (V) V (V) OUT OUT 05298-037 05298-036 05298-035 OUTPUT NOISE (nV/�Hz) 5μV/DIV 10μV/DIV 05298-039 05298-038 05298-040 AD5666 –20 V =5V DD T =25°C A –30 DAC LOADED WITH FULL SCALE CLR 3 V =2V± 0.3Vp-p REF –40 V F –50 OUT –60 –70 –80 V B OUT 4 4 –90 2 –100 2k 4k 6k 8k 10k CH2 1.0V M200ns A CH3 1.10V CH3 5.0V CH4 1.0V FREQUENCY (Hz) Figure 36. Total Harmonic Distortion Figure 38. Hardware CLR 16 5 V =5V DD V =V REF DD T =25°C A T =25°C 0 A 14 –5 V = 3V DD –10 12 –15 10 –20 V = 5V DD –25 8 –30 6 –35 4 –40 01 2 3 4 5 6 781 9 0 10k 100k 1M 10M CAPACITANCE (nF) FREQUENCY (Hz) Figure 37. Settling Time vs. Capacitive Load Figure 39. Multiplying Bandwidth Rev. D | Page 17 of 28 TIME (μs) (dB) 05298-042 05298-041 (dB) 05298-043 05298-044 AD5666 TERMINOLOGY Relative Accuracy Full-Scale Error For the DAC, relative accuracy, or integral nonlinearity (INL), is Full-scale error is a measure of the output error when full-scale a measure of the maximum deviation in LSBs from a straight code (0xFFFF) is loaded into the DAC register. Ideally, the line passing through the endpoints of the DAC transfer output should be VDD − 1 LSB. Full-scale error is expressed as a function. Figure 6 shows a plot of typical INL vs. code. percentage of the full-scale range. Figure 13 shows a plot of typical full-scale error vs. temperature. Differential Nonlinearity Differential nonlinearity (DNL) is the difference between the Digital-to-Analog Glitch Impulse measured change and the ideal 1 LSB change between any two Digital-to-analog glitch impulse is the impulse injected into the adjacent codes. A specified differential nonlinearity of ±1 LSB analog output when the input code in the DAC register changes maximum ensures monotonicity. This DAC is guaranteed mono- state. It is normally specified as the area of the glitch in nV-s tonic by design. Figure 7 shows a plot of typical DNL vs. code. and is measured when the digital input code is changed by 1 LSB at the major carry transition (0x7FFF to 0x8000). See Offset Error Figure 29. Offset error is a measure of the difference between the actual V and the ideal V , expressed in millivolts in the linear OUT OUT DC Power Supply Rejection Ratio (PSRR) region of the transfer function. Offset error is measured on the PSRR indicates how the output of the DAC is affected by changes AD5666 with Code 512 loaded into the DAC register. It can be in the supply voltage. PSRR is the ratio of the change in VOUT to negative or positive and is expressed in millivolts. a change in VDD for full-scale output of the DAC. It is measured in decibels. VREF is held at 2 V, and VDD is varied ±10%. Zero-Code Error Zero-code error is a measure of the output error when zero DC Crosstalk code (0x0000) is loaded into the DAC register. Ideally, the DC crosstalk is the dc change in the output level of one DAC in output should be 0 V. The zero-code error is always positive in response to a change in the output of another DAC. It is measured the AD5666, because the output of the DAC cannot go below 0 V. with a full-scale output change on one DAC (or soft power-down It is due to a combination of the offset errors in the DAC and and power-up) while monitoring another DAC kept at midscale. output amplifier. Zero-code error is expressed in millivolts. It is expressed in microvolts. Figure 13 shows a plot of typical zero-code error vs. DC crosstalk due to load current change is a measure of the temperature. impact that a change in load current on one DAC has to another Gain Error DAC kept at midscale. It is expressed in microvolts per milliamp. Gain error is a measure of the span error of the DAC. It is the Reference Feedthrough deviation in slope of the DAC transfer characteristic from the Reference feedthrough is the ratio of the amplitude of the signal ideal, expressed as a percentage of the full-scale range. at the DAC output to the reference input when the DAC output is not being updated (that is, is high). It is expressed in LDAC Zero-Code Error Drift decibels. Zero-code error drift is a measure of the change in zero-code error with a change in temperature. It is expressed in μV/°C. Digital Feedthrough Digital feedthrough is a measure of the impulse injected into Gain Error Drift the analog output of a DAC from the digital input pins of the Gain error drift is a measure of the change in gain error with device, but is measured when the DAC is not being written to changes in temperature. It is expressed in (ppm of full-scale (SYNC held high). It is specified in nV-s and measured with a range)/°C. full-scale change on the digital input pins, that is, from all 0s to all 1s or vice versa. Rev. D | Page 18 of 28 AD5666 Digital Crosstalk Multiplying Bandwidth Digital crosstalk is the glitch impulse transferred to the output The amplifiers within the DAC have a finite bandwidth. The of one DAC at midscale in response to a full-scale code change multiplying bandwidth is a measure of this. A sine wave on the (all 0s to all 1s or vice versa) in the input register of another reference (with full-scale code loaded to the DAC) appears on DAC. It is measured in standalone mode and is expressed in the output. The multiplying bandwidth is the frequency at nV-s. which the output amplitude falls to 3 dB below the input. Analog Crosstalk Total Harmonic Distortion (THD) Analog crosstalk is the glitch impulse transferred to the output Total harmonic distortion is the difference between an ideal of one DAC due to a change in the output of another DAC. It is sine wave and its attenuated version using the DAC. The sine measured by loading one of the input registers with a full-scale wave is used as the reference for the DAC, and the THD is a code change (all 0s to all 1s or vice versa) while keeping measure of the harmonics present on the DAC output. It is LDAC measured in decibels. high, and then pulsing LDAC low and monitoring the output of the DAC whose digital code has not changed. The area of the glitch is expressed in nV-s. DAC-to-DAC Crosstalk DAC-to-DAC crosstalk is 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 (all 0s to all 1s or vice versa) with low and monitoring the output of another DAC. The LDAC energy of the glitch is expressed in nV-s. Rev. D | Page 19 of 28 AD5666 THEORY OF OPERATION D/A SECTION R The AD5666 DAC is fabricated on a CMOS process. The archi- tecture consists of a string of DACs followed by an output buffer amplifier. The parts include an internal 1.25 V/2.5 V, 5 ppm/°C R reference with an internal gain of 2. Figure 40 shows a block diagram of the DAC architecture. TO OUTPUT R AMPLIFIER V DD REF (+) RESISTOR V DAC REGISTER OUT STRING OUTPUT REF (–) R AMPLIFIER (GAIN = +2) GND R Figure 40. DAC Architecture Because the input coding to the DAC is straight binary, the ideal Figure 41. Resistor String output voltage when using an external reference is given by INTERNAL REFERENCE D ⎛ ⎞ V = V × ⎜ ⎟ OUT REFIN N The AD5666 has an on-chip reference with an internal gain of 2. ⎝ 2 ⎠ The AD5666-1 has a 1.25 V 5 ppm/°C reference, giving a full-scale The ideal output voltage when using and internal reference is output of 2.5 V. The AD5666-2 has a 2.5 V 5 ppm/°C reference, given by giving a full-scale output of 5 V. The on-board reference is off at power-up, allowing the use of an external reference. The internal D ⎛ ⎞ = × × V2 V ⎜ ⎟ OUT REFOUT N reference is enabled via a write to a control register. ⎝ 2 ⎠ The internal reference associated with each part is available at where: the VREFOUT pin. A buffer is required if the reference output is D = decimal equivalent of the binary code that is loaded to the used to drive external loads. When using the internal reference, DAC register. it is recommended that a 100 nF capacitor be placed between 0 to 65,535 for AD5666 (16 bits). the reference output and GND for reference stability. N = the DAC resolution. Individual channel power-down is not supported while using RESISTOR STRING the internal reference. The resistor string section is shown in Figure 41. It is simply a string of resistors, each of value R. The code loaded into the DAC register determines at which node on the string the voltage is tapped off to be 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. D | Page 20 of 28 05298-023 05298-024 AD5666 Table 7. Command Definitions OUTPUT AMPLIFIER Command The output buffer amplifier can generate rail-to-rail voltages on C3 C2 C1 C0 Description its output, which gives an output range of 0 V to VDD. The 0 0 0 0 Write to Input Register n amplifier is capable of driving a load of 2 kΩ in parallel with 0 0 0 1 Update DAC Register n 1000 pF to GND. The source and sink capabilities of the output 0 0 1 0 Write to Input Register n, update all amplifier can be seen in Figure 19 and Figure 20. The slew rate (software LDAC) is 1.5 V/μs with a ¼ to ¾ scale settling time of 10 μs. 0 0 1 1 Write to and update DAC Channel n 0 1 0 0 Power down/power up DAC SERIAL INTERFACE 0 1 0 1 Load clear code register The AD5666 has a 3-wire serial interface ( , SCLK, and SYNC 0 1 1 0 Load LDAC register DIN) that is compatible with SPI, QSPI, and MICROWIRE 0 1 1 1 Reset (power-on reset) interface standards as well as most DSPs. See Figure 3 for a 1 0 0 0 Set up DCEN/REF register timing diagram of a typical write sequence. 1 0 0 1 No operation – – – – Reserved The write sequence begins by bringing the SYNC line low. Data 1 1 1 1 Reserved from the DIN line is clocked into the 32-bit shift register on the falling edge of SCLK. The serial clock frequency can be as high as 50 MHz, making the AD5666 compatible with high speed Table 8. Address Commands nd DSPs. On the 32 falling clock edge, the last data bit is clocked Address (n) in and the programmed function is executed, that is, a change Selected DAC in DAC register contents and/or a change in the mode of A3 A2 A1 A0 Channel operation. At this stage, the line can be kept low or be SYNC 0 0 0 0 DAC A brought high. In either case, it must be brought high for a 0 0 0 1 DAC B minimum of 15 ns before the next write sequence so that a 0 0 1 0 DAC C falling edge of SYNC can initiate the next write sequence. 0 0 1 1 DAC D Because the buffer draws more current when V = 2 V SYNC IN 1 1 1 1 All DACs than it does when VIN = 0.8 V, SYNC should be idled low between write sequences for even lower power operation of the part. As is mentioned previously, however, SYNC must be brought high again just before the next write sequence. Rev. D | Page 21 of 28 AD5666 INTERRUPT SYNC INPUT SHIFT REGISTER In a normal write sequence, the SYNC line is kept low for at The input shift register is 32 bits wide (see Figure 42). The first four bits are don’t cares. The next four bits are the command least 32 falling edges of SCLK, and the DAC is updated on the nd bits, C3 to C0 (see Table 8), followed by the 4-bit DAC address 32 falling edge. However, if is brought high before the SYNC nd bits, A3 to A0 (see Table 9) and finally the 16-bit data-word. 32 falling edge, this acts as an interrupt to the write sequence. The data-word comprises the 16-bit input code followed by four The shift register is reset, and the write sequence is seen as don’t care bits for the AD5666 (see Figure 42). These data bits invalid. Neither an update of the DAC register contents nor a nd are transferred to the DAC register on the 32 falling edge of change in the operating mode occurs (see Figure 43). SCLK. DB31 (MSB) DB0 (LSB) X XXX C3 C2 C1 C0 A3 A2 A1 A0 D15 D14 D13 D12 D11 D10 D9 D8 D7 D6 D5 D4 D3 D2 D1 D0 X X X X DATA BITS COMMAND BITS ADDRESS BITS Figure 42. AD5666 Input Register Content SCLK SYNC DB31 DB0 DB31 DB0 DIN INVALID WRITE SEQUENCE: VALID WRITE SEQUENCE, OUTPUT UPDATES SYNC HIGH BEFORE 32ND FALLING EDGE ON THE 32ND FALLING EDGE Figure 43. SYNC Interrupt Facility Rev. D | Page 22 of 28 05298-026 05298-025 AD5666 POWER-ON RESET DAISY-CHAINING The AD5666 contains a power-on reset circuit that controls the For systems that contain several DACs, or where the user output voltage during power-up. By connecting the POR pin wishes to read back the DAC contents for diagnostic purposes, low, the AD5666 output powers up to 0 V; by connecting the the SDO pin can be used to daisy-chain several devices together POR pin high, the AD5666 output powers up to midscale. The and provide serial readback. output remains powered up at this level until a valid write The daisy-chain mode is enabled through a software executable sequence is made to the DAC. This is useful in applications DCEN command. Command 1000 is reserved for this DCEN where it is important to know the state of the output of the DAC function (see Table 7). The daisy-chain mode is enabled by while it is in the process of powering up. There is also a software setting a bit (DB1) in the DCEN register. The default setting is executable reset function that resets the DAC to the power-on standalone mode, where Bit DCEN = 0. Table 9 shows how the reset code. Command 0111 is reserved for this reset function state of the bits corresponds to the mode of operation of the (see Table 7). Any events on LDAC or CLR during power-on device. reset are ignored. The SCLK is continuously applied to the input shift register POWER-DOWN MODES when is low. If more than 32 clock pulses are applied, the SYNC The AD5666 contains four separate modes of operation. data ripples out of the shift register and appears on the SDO Command 0100 is reserved for the power-down function (see line. This data is clocked out on the rising edge of SCLK and is Table 7). These modes are software-programmable by setting valid on the falling edge. By connecting this line to the DIN two bits, Bit DB19 and Bit DB18, in the control register. Table 11 input on the next DAC in the chain, a multi-DAC interface is shows how the state of the bits corresponds to the mode of constructed. Each DAC in the system requires 32 clock pulses; operation of the device. Any or all DACs (DAC D to DAC A) therefore, the total number of clock cycles must equal 32N, can be powered down to the selected mode by setting the cor- where N is the total number of devices in the chain. responding four bits (DB7, DB6, DB1, DB0) to 1. See Table 12 for the contents of the input shift register during power-down/ When the serial transfer to all devices is complete, SYNC is power-up operation. When using the internal reference, only taken high. This prevents any further data from being clocked all channel power-down to the selected modes is supported. into the input shift register. When both bits are set to 0, the part works normally with its If is taken high before 32 clocks are clocked into the part, SYNC normal power consumption of 700 μA at 5 V. However, for the it is considered an invalid frame and the data is discarded. three power-down modes, the supply current falls to 400 nA at 5 V (200 nA at 3 V). Not only does the supply current fall, but The serial clock can be continuous or a gated clock. A con- the output stage is also internally switched from the output of tinuous SCLK source can be used only if the can be held SYNC the amplifier to a resistor network of known values. This has the low for the correct number of clock cycles. In gated clock mode, advantage that the output impedance of the part is known while a burst clock containing the exact number of clock cycles must the part is in power-down mode. There are three different be used, and SYNC must be taken high after the final clock to options. The output is connected internally to GND through latch the data. either a 1 kΩ or a 100 kΩ resistor, or it is left open-circuited (three-state). The output stage is illustrated in Figure 44. INTERNAL REFERENCE REGISTER The on-board reference is off at power-up by default. This The bias generator, output amplifier, resistor string, and other allows the use of an external reference if the application requires associated linear circuitry are shut down when the power-down it. The on-board reference can be turned on/off by a user- mode is activated. The internal reference is powered down only programmable REF register by setting Bit DB0 high or low (see when all channels are powered down. However, the contents of Table 9). Command 1000 is reserved for this internal REF set- the DAC register are unaffected when in power-down. The time up command (see Table 7). Table 11 shows how the state of the to exit power-down is typically 4 μs for VDD = 5 V and for bits in the input shift register corresponds to the mode of VDD = 3 V (see Figure 28). operation of the device. Any combination of DACs can be powered up by setting PD1 and PD0 to 0 (normal operation). The output powers up to the value in the input register ( Low) or to the value in the LDAC DAC register before powering down (LDAC high). Rev. D | Page 23 of 28 AD5666 Table 9. Daisy-Chain Enable/Internal Reference Register DCEN (DB1) REF (DB0) Action 0 0 Standalone mode, reference off (default) 0 1 Standalone mode, reference on 1 0 DCEN mode, reference off 1 1 DCEN mode, reference on Table 10. 32-Bit Input Shift Register Contents for Daisy-Chain Enable and Reference Set-Up Function MSB LSB DB31 to DB28 DB27 DB26 DB25 DB24 DB23 DB22 DB21 DB20 DB19 to DB2 DB1 DB0 X 1 0 0 0 X X X X X 1/0 1/0 Don’t cares Command bits (C3 to C0) Address bits (A3 to A0) Don’t cares DCEN/REF register Table 11. Modes of Operation DB9 DB8 Operating Mode 0 0 Normal operation Power-down modes 0 1 1 kΩ to GND 1 0 100 kΩ to GND 1 1 Three-state Table 12. 32-Bit Input Shift Register Contents for Power-Up/Power-Down Function MSB LSB DB31 to DB19 to DB7 to DB28 DB27 DB26 DB25 DB24 DB23 DB22 DB21 DB20 DB10 DB9 DB8 DB4 DB3 DB2 DB1 DB0 X 0 1 0 0 X X X X X PD1 PD0 X DAC D DAC C DAC B DAC A Don’t Command bits (C2 to C0) Address bits (A3 to A0)— Don’t Power-down Don’t Power-down/power-up channel selection— cares don’t cares cares mode cares set bit to 1 to select RESISTOR AMPLIFIER V OUT STRING DAC POWER-DOWN RESISTOR CIRCUITRY NETWORK Figure 44. Output Stage During Power-Down Rev. D | Page 24 of 28 05298-027 AD5666 updates synchronously; that is, the DAC register is updated CLEAR CODE REGISTER after new data is read, regardless of the state of the pin. LDAC The AD5666 has a hardware CLR pin that is an asynchronous It effectively sees the LDAC pin as being tied low. (See Table 15 clear input. The input is falling edge sensitive. Bringing the CLR for the register mode of operation.) This flexibility is LDAC CLR line low clears the contents of the input register and the useful in applications where the user wants to simultaneously DAC registers to the data contained in the user-configurable update select channels while the rest of the channels are register and sets the analog outputs accordingly. This CLR synchronously updating. function can be used in system calibration to load zero scale, Writing to the DAC using command 0110 loads the 4-bit midscale, or full scale to all channels together. These clear code LDAC values are user-programmable by setting two bits, Bit DB1 and register (DB3 to DB0). The default for each channel is 0; that is, Bit DB0, in the control register (see Table 13). The default the LDAC pin works normally. Setting the bits to 1 means the setting clears the outputs to 0 V. Command 0101 is reserved for DAC channel is updated regardless of the state of the LDAC loading the clear code register (see Table 7). pin. See Table 16 for the contents of the input shift register during the load LDAC register mode of operation. nd The part exits clear code mode on the 32 falling edge of the next write to the part. If CLR is activated during a write POWER SUPPLY BYPASSING AND GROUNDING sequence, the write is aborted. When accuracy is important in a circuit, it is helpful to carefully consider the power supply and ground return layout on the The pulse activation time—the falling edge of to when CLR CLR board. The printed circuit board containing the AD5666 should the output starts to change—is typically 280 ns. However, if outside have separate analog and digital sections. If the AD5666 is in a the DAC linear region, it typically takes 520 ns after executing system where other devices require an AGND-to-DGND CLR for the output to start changing (see Figure 38). connection, the connection should be made at one point only. See Table 14 for contents of the input shift register during the This ground point should be as close as possible to the AD5666. loading clear code register operation The power supply to the AD5666 should be bypassed with 10 μF FUNCTION and 0.1 μF capacitors. The capacitors should physically be as LDAC close as possible to the device, with the 0.1 μF capacitor ideally The outputs of all DACs can be updated simultaneously using right up against the device. The 10 μF capacitors are the the hardware LDAC pin. tantalum bead type. It is important that the 0.1 μF capacitor has low effective series resistance (ESR) and low effective series Synchronous LDAC: After new data is read, the DAC registers nd inductance (ESI), such as is typical of common ceramic types of are updated on the falling edge of the 32 SCLK pulse. LDAC capacitors. This 0.1 μF capacitor provides a low impedance path can be permanently low or pulsed as in Figure 3. to ground for high frequencies caused by transient currents due to internal logic switching. Asynchronous : The outputs are not updated at the same LDAC time that the input registers are written to. When LDAC goes The power supply line should have as large a trace as possible to low, the DAC registers are updated with the contents of the provide a low impedance path and reduce glitch effects on the input register. supply line. Clocks and other fast switching digital signals should be shielded from other parts of the board by digital Alternatively, the outputs of all DACs can be updated ground. Avoid crossover of digital and analog signals if possible. simultaneously using the software function by writing to LDAC When traces cross on opposite sides of the board, ensure that Input Register n and updating all DAC registers. Command they run at right angles to each other to reduce feedthrough 0011 is reserved for this software LDAC function. effects through the board. The best board layout technique is the microstrip technique, where the component side of the An LDAC register gives the user extra flexibility and control board is dedicated to the ground plane only and the signal over the hardware LDAC pin. This register allows the user to traces are placed on the solder side. However, this is not always select which combination of channels to simultaneously update possible with a 2-layer board. when the hardware LDAC pin is executed. Setting the LDAC bit register to 0 for a DAC channel means that this channel’s update is controlled by the pin. If this bit is set to 1, this channel LDAC Rev. D | Page 25 of 28 AD5666 Table 13. Clear Code Register Clear Code Register DB1 DB0 CR1 CR0 Clears to Code 0 0 0x0000 0 1 0x8000 1 0 0xFFFF 1 1 No operation Table 14. 32-Bit Input Shift Register Contents for Clear Code Function MSB LSB DB31 to DB28 DB27 DB26 DB25 DB24 DB23 DB22 DB21 DB20 DB19 to DB2 DB1 DB0 X 0 1 0 1 X X X X X 1/0 1/0 Don’t cares Command bits (C3 to C0) Address bits (A3 to A0) Don’t cares Clear code register (CR1 to CR0) Table 15. LDAC Overwrite Definition Load DAC Register LDAC Bits (DB3 to DB0) LDAC Pin LDAC Operation 0 1/0 Determined by LDAC pin 1 X—don’t care DAC channels update, overrides the LDAC pin. DAC channels see LDAC as 0. Table 16. 32-Bit Input Shift Register Contents for LDAC Overwrite Function MSB LSB DB31 DB19 to to DB28 DB27 DB26 DB25 DB24 DB23 DB22 DB21 DB20 DB4 DB3 DB2 DB1 DB0 X 0 1 1 0 X X X X X DAC D DAC C DAC B DAC A Don’t Command bits (C3 to C0) Address bits (A3 to A0)— Don’t Setting LDAC bit to 1 override LDAC pin cares don’t cares cares Rev. D | Page 26 of 28 AD5666 OUTLINE DIMENSIONS 5.10 5.00 4.90 14 8 4.50 6.40 4.40 BSC 4.30 1 7 PIN 1 0.65 BSC 1.05 1.20 1.00 0.20 MAX 0.80 0.09 0.75 0.15 8° 0.60 SEATING 0° 0.05 0.45 0.30 PLANE COPLANARITY 0.19 0.10 COMPLIANT TO JEDEC STANDARDS MO-153-AB-1 Figure 45. 14-Lead Thin Shrink Small Outline Package [TSSOP] (RU-14) Dimensions shown in millimeters ORDERING GUIDE Package Power-On Internal 1 Model Temperature Range Package Description Option Reset to Code Accuracy Reference AD5666BRUZ-1 −40°C to +105°C 14-Lead TSSOP RU-14 Zero ±16 LSB INL 1.25 V AD5666BRUZ-1REEL7 −40°C to +105°C 14-Lead TSSOP RU-14 Zero ±16 LSB INL 1.25 V AD5666BRUZ-2 −40°C to +105°C 14-Lead TSSOP RU-14 Zero ±16 LSB INL 2.5 V AD5666BRUZ-2REEL7 −40°C to +105°C 14-Lead TSSOP RU-14 Zero ±16 LSB INL 2.5 V AD5666ARUZ-2 −40°C to +105°C 14-Lead TSSOP RU-14 Zero ±32 LSB INL 2.5 V AD5666ARUZ-2REEL7 −40°C to +105°C 14-Lead TSSOP RU-14 Zero ±32 LSB INL 2.5 V EVAL-AD5666EBZ Evaluation Board 1 Z = RoHS Compliant Part. Rev. D | Page 27 of 28 061908-A AD5666 NOTES ©2005–2010 Analog Devices, Inc. All rights reserved. Trademarks and registered trademarks are the property of their respective owners. D05298–0–6/10(D) Rev. D | Page 28 of 28