Quad Channel, 16-Bit, Serial Input, 4 mA to 20 mA and Voltage Output DAC, Dynamic Power Control, HART Connectivity AD5755-1 Data Sheet in current mode. This is achieved by regulating the voltage on the output driver from 7.4 V to 29.5 V using a dc-to-dc boost converter optimized for minimum on-chip power dissipation. Each channel has a corresponding CHART pin so that HART signals can be coupled onto the current output of the AD5755-1. FEATURES 16-bit resolution and monotonicity Dynamic power control for thermal management Current and voltage output pins connectable to a single terminal Current output ranges: 0 mA to 20 mA, 4 mA to 20 mA, or 0 mA to 24 mA ±0.05% total unadjusted error (TUE) maximum Voltage output ranges (with 20% overrange): 0 V to 5 V, 0 V to 10 V, ±5 V, and ±10 V ±0.04% total unadjusted error (TUE) maximum User programmable offset and gain On-chip diagnostics On-chip reference (±10 ppm/°C maximum) −40°C to +105°C temperature range The device uses a versatile 3-wire serial interface that operates at clock rates of up to 30 MHz and is compatible with standard SPI, QSPI™, MICROWIRE™, DSP, and microcontroller interface standards. The interface also features optional CRC-8 packet error checking, as well as a watchdog timer that monitors activity on the interface. PRODUCT HIGHLIGHTS 1. 2. 3. 4. APPLICATIONS Process control Actuator control Programmable logic controllers (PLCs) HART network connectivity Dynamic power control for thermal management. 16-bit performance. Multichannel. HART compliant. COMPANION PRODUCTS Product Family: AD5755, AD5757 HART Modem: AD5700, AD5700-1 External References: ADR445, ADR02 Digital Isolators: ADuM1410, ADuM1411 Power: ADP2302, ADP2303 Additional companion products on the AD5755-1 product page GENERAL DESCRIPTION The AD5755-1 is a quad, voltage and current output DAC that operates with a power supply range from −26.4 V to +33 V. Onchip dynamic power control minimizes package power dissipation FUNCTIONAL BLOCK DIAGRAM AVCC 5.0V AVSS –15V/0V AGND AVDD +15V SWx DVDD VBOOST_x 7.4V TO 29.5V DGND LDAC DC-TO-DC CONVERTER SCLK SDIN SYNC SDO CLEAR DIGITAL INTERFACE IOUT_x + FAULT ALERT GAIN REG A OFFSET REG A AD1 AD0 DAC A CURRENT AND VOLTAGE OUTPUT RANGE SCALING RSET_x CHARTx +VSENSE_x VOUT _x DAC CHANNEL A REFERENCE REFIN DAC CHANNEL B DAC CHANNEL C AD5755-1 09226-101 REFOUT DAC CHANNEL D NOTES 1. x = A, B, C, AND D. Figure 1. Rev. F Document Feedback 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. 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Technical Support www.analog.com AD5755-1 Data Sheet TABLE OF CONTENTS Features .............................................................................................. 1 Readback Operation .................................................................. 38 Applications ....................................................................................... 1 Device Features ............................................................................... 41 General Description ......................................................................... 1 Output Fault ................................................................................ 41 Product Highlights ........................................................................... 1 Voltage Output Short-Circuit Protection ................................ 41 Companion Products ....................................................................... 1 Digital Offset and Gain Control ............................................... 41 Functional Block Diagram .............................................................. 1 Status Readback During a Write .............................................. 41 Revision History ............................................................................... 3 Asynchronous Clear................................................................... 42 Detailed Functional Block Diagram .............................................. 4 Packet Error Checking ............................................................... 42 Specifications..................................................................................... 5 Watchdog Timer ......................................................................... 42 AC Performance Characteristics ................................................ 8 Output Alert ................................................................................ 42 Timing Characteristics ................................................................ 9 Internal Reference ...................................................................... 42 Absolute Maximum Ratings.......................................................... 12 External Current Setting Resistor ............................................ 42 ESD Caution ................................................................................ 12 HART Connectivity ................................................................... 43 Pin Configuration and Function Descriptions ........................... 13 Digital Slew Rate Control .......................................................... 43 Typical Performance Characteristics ........................................... 16 Power Dissipation control ......................................................... 44 Voltage Outputs .......................................................................... 16 DC-to-DC Converters ............................................................... 44 Current Outputs ......................................................................... 20 AICC Supply Requirements—Static .......................................... 45 DC-to-DC Block......................................................................... 24 AICC Supply Requirements—Slewing ...................................... 45 Reference ..................................................................................... 25 Applications Information .............................................................. 47 General ......................................................................................... 26 Voltage and Current Output Ranges on the Same Terminal 47 Terminology .................................................................................... 27 Current Output Mode with Internal RSET ................................ 47 Theory of Operation ...................................................................... 29 Precision Voltage Reference Selection ..................................... 47 DAC Architecture ....................................................................... 29 Driving Inductive Loads ............................................................ 48 Power-On State of the AD5755-1 ............................................. 29 Transient Voltage Protection .................................................... 48 Serial Interface ............................................................................ 30 Microprocessor Interfacing ....................................................... 48 Transfer Function ....................................................................... 30 Layout Guidelines....................................................................... 48 Registers ........................................................................................... 31 Galvanically Isolated Interface ................................................. 49 Programming Sequence to Write/Enable the Output Correctly ...................................................................................... 32 Industrial HART Capable Analog Output Application— Shared VOUT_x and IOUT_x Pin...................................................... 50 Changing and Reprogramming the Range ............................. 32 Outline Dimensions ....................................................................... 51 Data Registers ............................................................................. 33 Ordering Guide .......................................................................... 51 Control Registers ........................................................................ 35 Rev. F | Page 2 of 51 Data Sheet AD5755-1 REVISION HISTORY 9/14—Rev. E to Rev. F 5/12—Rev. B to Rev. C Changes to Thermal Hysteresis Parameter, Table 1...................... 7 Changes to Table 3 ............................................................................ 9 Changes to Figure 4.........................................................................10 Added Figure 5; Renumbered Sequentially .................................11 Changes to Table 5 ..........................................................................14 Changes to Figure 56 through Figure 59 ......................................24 Change to Figure 70 and Figure 71 ...............................................26 Change to Voltage Reference Thermal Hysteresis Definition ........27 Changes to Table 7 ..........................................................................31 Changes to Offset Register Section, Table 12, and Table 14 ......34 Changes to Software Register Section, Table 22, and Table 23 .......37 Changes to Readback Operation Section, Added Table 28 and Table 29; Renumbered Sequentially ..............................................38 Changes to Status Register Section, Table 31, and Table 32 ......40 Changes to Status Readback During a Write Section .................41 Changes to Packet Error Checking Section .................................42 Changes to HART Connectivity Section......................................43 Changes to Table 36 ........................................................................44 Changes to Companion Products Section ..................................... 1 Changes to Figure 2 .......................................................................... 3 Changes to Table 5 .......................................................................... 15 Changes to Figure 22 ...................................................................... 18 Added Industrial HART Capable Analog Output Application— Shared VOUT_x and IOUT_X Pin Section and Figure 89, Renumbered Sequentially .............................................................. 49 Updated Outline Dimensions........................................................ 50 11/12—Rev. D to Rev. E Changes to Figure 2........................................................................... 4 Changed Thermal Impedance from 20°C/W to 28°C/W ..........12 Changes to Pin 6 Description ........................................................13 Changes to Pin 27 Description ......................................................14 Changes to Figure 26 ......................................................................19 Changes to DUT_AD1, DUT_AD0 Description, Table 9 .........33 Changes to Packet Error Checking Section and Internal Reference Section ............................................................................41 Changes to Figure 81 ......................................................................43 Changes to Figure 86 ......................................................................47 Changes to Figure 89 ......................................................................49 7/12—Rev. C to Rev. D Changes to Figure 89 ...................................................................... 49 Updated Outline Dimensions ........................................................ 50 11/11—Rev. A to Rev. B Removed Voltage Output Test Conditions/Comments, Table 1.... 5 Changed Headroom and Footroom Test Conditions/Comments, Table 1 .......................................................................................................... 5 Changes to Figure 4 ........................................................................ 10 Changes to Figure 5 ........................................................................ 11 Changes to SCLK Description, Table 5 ........................................ 13 Changes to Figure 12 ...................................................................... 16 Changes to Figure 21 ...................................................................... 18 Changes to Figure 37 ...................................................................... 20 Changes to Figure 44 ...................................................................... 22 Changes to Figure 71 ...................................................................... 29 Changes to Power-On State of the AD5755-1 Section ............... 30 Changes to Table 17 ........................................................................ 35 Changes to Readback Operation section and Table 26 .............. 38 Changes to Voltage Output Short-Circuit Protection Section .. 40 Changes to Figure 78 ...................................................................... 41 Changes to Figure 82 ...................................................................... 44 Changes to Figure 83, Figure 84, and Figure 85 ................................. 45 Changes to Transient Voltage Protection Section and Figure 86 ... 47 Changes to Galvanically Isolated Interface Section .................... 48 5/11—Rev. 0 to Rev. A Removed Endnote 6 (Table 1) ......................................................... 6 Changed AVDD Minimum Value from 10.8 V to 9 V ................... 6 Changed AISS Minimum Value from −1.4 mA to −1.7 mA......... 7 Changed AVDD Voltage in Pin 19 Description ............................ 13 Changes to Ordering Guide ........................................................... 48 4/11—Revision 0: Initial Version Rev. F | Page 3 of 51 AD5755-1 Data Sheet DETAILED FUNCTIONAL BLOCK DIAGRAM AV CC 5.0V AV SS –15V/0V AGND DVDD DGND LDAC CLEAR SCLK SDIN SYNC SDO AV DD +15V SWA POWER-ON RESET DC-TO-DC CONVERTER POWER CONTROL INPUT SHIFT REGISTER AND CONTROL FAULT STATUS REGISTER VBOOST_A 16 INPUT REG A DAC REG A 16 7.4V TO 29.5V VSEN1 REG R2 VSEN2 R3 DAC A GAIN REG A OFFSET REG A IOUT_A R1 ALERT REFOUT REFIN WATCHDOG TIMER (SPI ACTIVITY) RSET_A CHARTA 30kΩ VREF VOUT RANGE SCALING +VSENSE_A VOUT_A REFERENCE BUFFERS DAC CHANNEL A RSET_B, RSET_C, RSET_D AD5755-1 DAC CHANNEL B DAC CHANNEL C DAC CHANNEL D +VSENSE_B, +VSENSE_C, +VSENSE_D IOUT_B, IOUT_C, IOUT_D AD0 CHARTB, CHARTC, CHARTD VOUT_B, VOUT_C, VOUT_D SWB, SWC, SWD Figure 2. Rev. F | Page 4 of 51 VBOOST_B, VBOOST_C, VBOOST_D 09226-001 AD1 Data Sheet AD5755-1 SPECIFICATIONS AVDD = VBOOST_x = 15 V; AVSS = −15 V/0 V; DVDD = 2.7 V to 5.5 V; AVCC = 4.5 V to 5.5 V; dc-to-dc converter disabled; AGND = DGND = GNDSWx = 0 V; REFIN = 5 V; voltage outputs: RL = 1 kΩ, CL = 220 pF; current outputs: RL = 300 Ω; all specifications TMIN to TMAX, unless otherwise noted. Table 1. Parameter 1 VOLTAGE OUTPUT Output Voltage Ranges ACCURACY BIPOLAR SUPPLY Resolution Total Unadjusted Error (TUE) TUE Long-Term Stability Relative Accuracy (INL) Differential Nonlinearity (DNL) Zero-Scale Error Zero-Scale TC 2 Bipolar Zero Error Bipolar Zero TC2 Offset Error Offset TC2 Gain Error Gain TC2 Full-Scale Error Full-Scale TC2 ACCURACY UNIPOLAR SUPPLY2 Total Unadjusted Error (TUE) Relative Accuracy (INL) 3 Differential Nonlinearity (DNL) Zero-Scale Error Offset Error Gain Error Full-Scale Error OUTPUT CHARACTERISTICS2 Headroom Footroom Min 0 0 −5 −10 0 0 −6 −12 Max Unit 5 10 +5 +10 6 12 +6 +12 V V V V V V V V Test Conditions/Comments AVSS = −15 V, loaded and unloaded 16 −0.04 −0.03 −0.006 −0.008 −1 −0.03 −0.03 −0.03 −0.03 −0.03 ±0.0032 35 ±0.0012 ±0.0012 ±0.002 ±2 ±0.002 ±1 ±0.002 ±2 ±0.004 ±3 ±0.002 ±2 +0.04 +0.03 +0.006 +0.008 +1 +0.03 +0.03 +0.03 +0.03 +0.03 Bits % FSR % FSR ppm FSR % FSR % FSR LSB % FSR ppm FSR/°C % FSR ppm FSR/°C % FSR ppm FSR/°C % FSR ppm FSR/°C % FSR ppm FSR/°C TA = 25°C Drift after 1000 hours, TJ = 150°C 0 V to 5 V, 0 V to 10 V, ±5 V, ±10 V ranges On overranges Guaranteed monotonic AVSS = 0 V −0.06 −0.009 −1 −0.07 −0.07 −0.06 Output Voltage Drift vs. Time Short-Circuit Current 12/6 Load Capacitive Load Stability 1 DC Output Impedance DC PSRR DC Crosstalk Typ ±0.025 +0.06 +0.009 +1 +0.22 ±0.025 ±0.015 ±0.015 +0.07 +0.07 +0.06 % FSR % FSR LSB % FSR % FSR % FSR % FSR 1 0.7 2.2 1.4 V V 20 ppm FSR 16/8 mA 10 2 0.06 50 24 kΩ nF µF Ω µV/V µV Rev. F | Page 5 of 51 Guaranteed monotonic With respect to VBOOST supply With respect to the AVSS supply, bipolar output ranges Drift after 1000 hours, ¾ scale output, TJ = 150°C, AVSS = −15 V Programmable by user, defaults to 16 mA typical level For specified performance External compensation capacitor of 220 pF connected AD5755-1 Parameter 1 CURRENT OUTPUT Output Current Ranges Resolution ACCURACY (EXTERNAL RSET) Total Unadjusted Error (TUE) TUE Long-Term Stability Relative Accuracy (INL) Differential Nonlinearity (DNL) Offset Error Offset Error Drift2 Gain Error Gain TC2 Full-Scale Error Full-Scale TC2 DC Crosstalk ACCURACY (INTERNAL RSET) Total Unadjusted Error (TUE) 4, 5 TUE Long-Term Stability Relative Accuracy (INL) Relative Accuracy (INL) Differential Nonlinearity (DNL) Offset Error4, 5 Offset Error Drift2 Gain Error Gain TC2 Full-Scale Error4, 5 Full-Scale TC2 DC Crosstalk5 OUTPUT CHARACTERISTICS2 Current Loop Compliance Voltage Data Sheet Min Typ 0 0 4 16 Max Unit 24 20 20 mA mA mA Bits Assumes ideal resistor, see the External Current Setting Resistor section for more information −0.05 −0.006 −1 −0.05 −0.05 −0.05 −0.14 −0.11 −0.006 −0.004 −1 −0.05 −0.04 −0.12 −0.06 −0.14 −0.1 ±0.009 100 ±0.005 ±4 ±0.004 ±3 ±0.008 ±5 0.0005 ±0.009 180 ±0.007 ±6 ±0.002 ±9 ±0.007 ±14 −0.011 VBOOST_x − 2.4 +0.05 +0.006 +1 +0.05 +0.05 +0.05 +0.14 +0.11 +0.006 +0.004 +1 +0.05 +0.04 +0.12 +0.06 +0.14 +0.1 VBOOST_x − 2.7 % FSR ppm FSR % FSR LSB % FSR ppm FSR/°C % FSR ppm FSR/°C % FSR ppm FSR/°C % FSR % FSR % FSR ppm FSR % FSR % FSR LSB % FSR % FSR ppm FSR/°C % FSR % FSR ppm FSR/°C % FSR % FSR ppm FSR/°C % FSR 90 140 Resistive Load 100 0.02 Drift after 1000 hours, TJ = 150°C Guaranteed monotonic External RSET TA = 25°C Drift after 1000 hours, TJ = 150°C TA = 25°C Guaranteed monotonic TA = 25°C TA = 25°C TA = 25°C Internal RSET V Output Current Drift vs. Time Output Impedance DC PSRR Test Conditions/Comments 1000 ppm FSR ppm FSR Ω 1 MΩ µA/V Rev. F | Page 6 of 51 Drift after 1000 hours, ¾ scale output, TJ = 150°C External RSET Internal RSET The dc-to-dc converter has been characterized with a maximum load of 1 kΩ, chosen such that compliance is not exceeded; see Figure 54 and DC-DC MaxV bits in Table 25 Data Sheet Parameter 1 REFERENCE INPUT/OUTPUT Reference Input2 Reference Input Voltage DC Input Impedance Reference Output Output Voltage Reference TC2 Output Noise (0.1 Hz to 10 Hz)2 Noise Spectral Density2 Output Voltage Drift vs. Time2 Capacitive Load2 Load Current Short-Circuit Current Line Regulation2 Load Regulation2 Thermal Hysteresis2 DC-TO-DC Switch Switch On Resistance Switch Leakage Current Peak Current Limit Oscillator Oscillator Frequency Maximum Duty Cycle DIGITAL INPUTS2 VIH, Input High Voltage VIL, Input Low Voltage Input Current Pin Capacitance DIGITAL OUTPUTS2 SDO, ALERT VOL, Output Low Voltage VOH, Output High Voltage High Impedance Leakage Current High Impedance Output Capacitance FAULT VOL, Output Low Voltage VOL, Output Low Voltage VOH, Output High Voltage POWER REQUIREMENTS AVDD AVSS DVDD AVCC AD5755-1 Min Typ Max Unit Test Conditions/Comments 4.95 45 5 150 5.05 V MΩ For specified performance 4.995 −10 5 ±5 7 100 180 1000 9 10 3 95 200 5.005 +10 V ppm/°C µV p-p nV/√Hz ppm nF mA mA ppm/V ppm/mA ppm TA = 25°C 0.425 10 0.8 11.5 13 14.5 0.8 +1 2.6 0.4 +1 2.5 See Figure 65 See Figure 65 V V µA pF V V µA This oscillator is divided down to give the dc-to-dc converter switching frequency At 410 kHz dc-to-dc switching frequency JEDEC compliant Per pin Per pin Sinking 200 µA Sourcing 200 µA pF 0.4 V V V 33 −10.8/0 5.5 5.5 V V V V 0.6 3.6 9 −26.4 2.7 4.5 MHz % 2 DVDD − 0.5 −1 See Figure 65 Ω nA A 89.6 −1 At 10 kHz Drift after 1000 hours, TJ = 150°C Rev. F | Page 7 of 51 10 kΩ pull-up resistor to DVDD At 2.5 mA 10 kΩ pull-up resistor to DVDD AD5755-1 Parameter 1 AIDD AISS Data Sheet Min −11 Typ 8.6 Max 10.5 Unit mA 7 −8.8 7.5 mA mA 9.2 11 mA mA 1 2.7 mA mA 1 mA mW −1.7 DICC AICC IBOOST IBOOST 6 Power Dissipation 173 Test Conditions/Comments Voltage output mode on all channels, output unloaded, over supplies Current output mode on all channels Voltage output mode on all channels, output unloaded, over supplies Current output mode on all channels VIH = DVDD, VIL = DGND, internal oscillator running, over supplies Output unloaded, over supplies Per channel, voltage output mode, output unloaded, over supplies Per channel, current output mode, 0 mA output AVDD = +15 V, AVSS = −15 V, dc-to-dc converter enable, current output mode, outputs disabled Temperature range: −40°C to +105°C; typical at +25°C. Guaranteed by design and characterization; not production tested. 3 For voltage output ranges in unipolar supply mode, the INL and TUE are measured beginning from Code 4096. 4 For current outputs with internal RSET, the offset, full-scale, and TUE measurements exclude dc crosstalk. The measurements are made with all four channels enabled loaded with the same code. 5 See the Current Output Mode with Internal RSET section for more explanation of the dc crosstalk. 6 Efficiency plots in Figure 56, Figure 57, Figure 58, and Figure 59 include the IBOOST quiescent current. 1 2 AC PERFORMANCE CHARACTERISTICS AVDD = VBOOST_x = 15 V; AVSS = −15 V; DVDD = 2.7 V to 5.5 V; AVCC = 4.5 V to 5.5 V; dc-to-dc converter disabled; AGND = DGND = GNDSWx = 0 V; REFIN = 5 V; voltage outputs: RL = 2 kΩ, CL = 220 pF; current outputs: RL = 300 Ω; all specifications TMIN to TMAX, unless otherwise noted. Table 2. Parameter 1 DYNAMIC PERFORMANCE Voltage Output Output Voltage Settling Time Min Typ Max Unit Test Conditions/Comments 1.9 150 6 25 1 2 0.15 µs µs µs V/µs nV-sec nV-sec mV nV-sec nV-sec LSB p-p 5 V step to ±0.03% FSR, 0 V to 5 V range 10 V step to ±0.03% FSR, 0 V to 10 V range 100 mV step to 1 LSB (16-bit LSB), 0 V to 10 V range 0 V to 10 V range 150 83 nV/√Hz dB Measured at 10 kHz, midscale output, 0 V to 10 V range 200 mV 50 Hz/60 Hz sine wave superimposed on power supply voltage 15 See test conditions/ comments 0.15 µs ms To 0.1% FSR (0 mA to 24 mA) See Figure 50, Figure 51, and Figure 52 LSB p-p 16-bit LSB, 0 mA to 24 mA range 0.5 nA/√Hz Measured at 10 kHz, midscale output, 0 mA to 24 mA range 11 18 13 Slew Rate Power-On Glitch Energy Digital-to-Analog Glitch Energy Glitch Impulse Peak Amplitude Digital Feedthrough DAC to DAC Crosstalk Output Noise (0.1 Hz to 10 Hz Bandwidth) Output Noise Spectral Density AC PSRR Current Output Output Current Settling Time Output Noise (0.1 Hz to 10 Hz Bandwidth) Output Noise Spectral Density 1 Guaranteed by design and characterization; not production tested. Rev. F | Page 8 of 51 0 V to 10 V range 16-bit LSB, 0 V to 10 V range Data Sheet AD5755-1 TIMING CHARACTERISTICS AVDD = VBOOST_x = 15 V; AVSS = −15 V; DVDD = 2.7 V to 5.5 V; AVCC = 4.5 V to 5.5 V; dc-to-dc converter disabled; AGND = DGND = GNDSWx = 0 V; REFIN = 5 V; voltage outputs: RL = 1 kΩ, CL = 220 pF; current outputs: RL = 300 Ω; all specifications TMIN to TMAX, unless otherwise noted. Table 3. Parameter 1, 2, 3 t1 t2 t3 t4 t5 t6 t7 t8 t9 t10 t11 t12 t13 t14 t15 t16 t17 t18 t19 Limit at TMIN, TMAX 50 17 17 20 15 198 5 15 10 20 Unit ns min ns min ns min ns min ns min ns min µs min ns min ns min µs min 5 10 500 See the AC Performance Characteristics section 1 7 40 5 500 1 20 µs min ns min ns max µs max 5 µs min µs min µs max ns max µs min ns min µs min µs min Description SCLK cycle time SCLK high time SCLK low time SYNC falling edge to SCLK falling edge setup time 24th/32nd SCLK falling edge to SYNC rising edge (see Figure 79) SYNC high time following a configuration write SYNC high time following a DAC update write Data setup time Data hold time SYNC rising edge to LDAC falling edge (applies to any channel with digital slew rate control enabled; single DAC updated) SYNC rising edge to LDAC falling edge (single DAC updated) LDAC pulse width low LDAC falling edge to DAC output response time DAC output settling time CLEAR high time CLEAR activation time SCLK rising edge to SDO valid SYNC rising edge to DAC output response time (LDAC = 0) (single DAC updated) LDAC falling edge to SYNC rising edge RESET pulse width SYNC rising edge to next SYNC falling edge (digital slew rate control enabled; single DAC updated) SYNC rising edge to next SYNC falling edge (digital slew rate control disabled; single DAC updated) Guaranteed by design and characterization; not production tested. All input signals are specified with tR = tF = 5 ns (10% to 90% of DVDD) and timed from a voltage level of 1.2 V. 3 See Figure 3, Figure 4, Figure 6, and Figure 7. 1 2 Rev. F | Page 9 of 51 AD5755-1 Data Sheet Timing Diagrams t1 SCLK 1 2 24 t3 t6 t2 t4 t5 SYNC t8 t7 SDIN t19 MSB LSB t10 t10 t9 LDAC t17 t12 t11 VOUT_x LDAC = 0 t12 t16 VOUT_x t13 CLEAR t14 VOUT_x 09226-002 t18 RESET Figure 3. Serial Interface Timing Diagram SCLK 24 1 24 1 t6 SYNC LSB MSB LSB MSB NOP CONDITION INPUT WORD SPECIFIES REGISTER TO BE READ MSB SDO LSB UNDEFINED t15 SELECTED REGISTER DATA CLOCKED OUT 1IF FIRST SCLK IS NEGATIVE EDGE WITHIN SYNC FRAME OF NOP CONDITION, 7 DON’T CARE BITS + 16 DATA BITS CLOCKED OUT (TOTAL 23 BITS). IF FIRST SCLK IS POSITIVE EDGE WITHIN SYNC FRAME OF NOP CONDITION, 8 DON’T CARE BITS + 16 DATA BITS CLOCKED OUT (TOTAL 24 BITS). SEE THE READBACK OPERATION SECTION FOR FURTHER INFORMATION. Figure 4. Readback Timing Diagram (Packet Error Checking Disabled) Rev. F | Page 10 of 51 09226-003 SDIN Data Sheet SCLK AD5755-1 1 24 1 32 24 32 2 t6 SYNC MSB SDIN LSB CRC7 CRC0 MSB CRC7 CRC0 8-BIT CRC NOP CONDITION 8-BIT CRC INPUT WORD SPECIFIES REGISTER TO BE READ LSB MSB SDO LSB 8-BIT CRC t15 UNDEFINED SELECTED REGISTER DATA CLOCKED OUT1 IF FIRST SCLK IS POSITIVE EDGE WITHIN SYNC FRAME OF NOP CONDITION, 8 DONT CARE BITS + 16 DATA BITS CLOCKED OUT + 8 CRC BITS (TOTAL 32 BITS). 2 AVOID SCLK ACTIVITY DURING t AS IT MAY RESULT IN A PEC ERROR ON READBACK. 6 SEE THE READBACK OPERATION AND PACKET ERROR CHECKING SECTIONS FOR FURTHER INFORMATION. 09226-105 1IF FIRST SCLK IS NEGATIVE EDGE WITHIN SYNC FRAME OF NOP CONDITION, 7 DONT CARE BITS + 16 DATA BITS CLOCKED OUT + 8 CRC BITS (TOTAL 31 BITS). Figure 5. Readback Timing Diagram (Packet Error Checking Enabled) LSB 1 MSB 24 2 SCLK SDO R/W DUT_ AD1 DUT_ AD0 SDO DISABLED X X X D15 D14 D1 D0 SDO_ ENAB STATUS STATUS STATUS STATUS Figure 6. Status Readback During Write 200µA TO OUTPUT PIN IOL VOH (MIN) OR VOL (MAX) CL 50pF 200µA IOH Figure 7. Load Circuit for SDO Timing Diagram Rev. F | Page 11 of 51 09226-005 SDIN 09226-004 SYNC AD5755-1 Data Sheet ABSOLUTE MAXIMUM RATINGS TA = 25°C, unless otherwise noted. Transient currents of up to 100 mA do not cause SCR latch-up. Table 4. Parameter AVDD, VBOOST_x to AGND, DGND AVSS to AGND, DGND AVDD to AVSS AVCC to AGND DVDD to DGND Digital Inputs to DGND Digital Outputs to DGND REFIN, REFOUT to AGND VOUT_x to AGND +VSENSE_x to AGND IOUT_x to AGND SWx to AGND AGND, GNDSWx to DGND Operating Temperature Range (TA) Industrial1 Storage Temperature Range Junction Temperature (TJ max) 64-Lead LFCSP θJA Thermal Impedance2 Power Dissipation Lead Temperature Soldering 1 2 Rating −0.3 V to +33 V +0.3 V to −28 V −0.3 V to +60 V −0.3 V to +7 V −0.3 V to +7 V −0.3 V to DVDD + 0.3 V or +7 V (whichever is less) −0.3 V to DVDD + 0.3 V or +7 V (whichever is less) −0.3 V to AVDD + 0.3 V or +7 V (whichever is less) AVSS to VBOOST_x or 33 V if using the dc-to-dc circuitry AVSS to VBOOST_x or 33 V if using the dc-to-dc circuitry AVSS to VBOOST_x or 33 V if using the dc-to-dc circuitry −0.3 to +33 V −0.3 V to +0.3 V Stresses above those listed under Absolute Maximum Ratings may cause permanent damage to the device. This is a stress rating only; functional operation of the device at these or any other conditions above those indicated in the operational section of this specification is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability. ESD CAUTION −40°C to +105°C −65°C to +150°C 125°C 28°C/W (TJ max − TA)/θJA JEDEC industry standard J-STD-020 Power dissipated on chip must be derated to keep the junction temperature below 125°C. Based on a JEDEC 4-layer test board. Rev. F | Page 12 of 51 Data Sheet AD5755-1 64 63 62 61 60 59 58 57 56 55 54 53 52 51 50 49 RSET_C RSET_D REFOUT REFIN COMPLV_D CHARTD +VSENSE_D COMPDCDC_D VBOOST_D VOUT_D IOUT_D AVSS COMPLV_C CHARTC +VSENSE_C VOUT_C PIN CONFIGURATION AND FUNCTION DESCRIPTIONS PIN 1 INDICATOR 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 AD5755-1 TOP VIEW (Not to Scale) 48 47 46 45 44 43 42 41 40 39 38 37 36 35 34 33 COMPDCDC_C IOUT_C VBOOST_C AVCC SWC GNDSWC GNDSWD SWD AVSS SWA GNDSWA GNDSWB SWB AGND VBOOST_B IOUT_B NOTES 1. THE EXPOSED PAD SHOULD BE CONNECTED TO THE POTENTIAL OF THE AVSS PIN, OR, ALTERNATIVELY, IT CAN BE LEFT ELECTRICALLY UNCONNECTED. IT IS RECOMMENDED THAT THE PAD BE THERMALLY CONNECTED TO A COPPER PLANE FOR ENHANCED THERMAL PERFORMANCE. 09266-006 POC RESET AVDD COMPLV_A CHARTA +VSENSE_A COMPDCDC_A VBOOST_A VOUT_A IOUT_A AVSS COMPLV_B CHARTB +VSENSE_B VOUT_B COMPDCDC_B 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 RSET_B RSET_A REFGND REFGND AD0 AD1 SYNC SCLK SDIN SDO DVDD DGND LDAC CLEAR ALERT FAULT Figure 8. Pin Configuration Table 5. Pin Function Descriptions Pin No. 1 Mnemonic RSET_B 2 RSET_A 3, 4 5 6 REFGND AD0 AD1 7 SYNC 8 SCLK 9 10 11 12 13 SDIN SDO DVDD DGND LDAC 14 CLEAR Description An external, precision, low drift 15 kΩ current setting resistor can be connected to this pin to improve the IOUT_B temperature drift performance. See the Device Features section. An external, precision, low drift 15 kΩ current setting resistor can be connected to this pin to improve the IOUT_A temperature drift performance. See the Device Features section. Ground Reference Point for Internal Reference. Address Decode for the Device Under Test (DUT) on the Board. Address Decode for the DUT on the Board. It is not recommended to tie both AD1 and AD0 low when using PEC, see the Packet Error Checking section. Active Low Input. This is the frame synchronization signal for the serial interface. While SYNC is low, data is transferred in on the falling edge of SCLK. Serial Clock Input. Data is clocked into the input shift register on the falling edge of SCLK. This operates at clock speeds of up to 30 MHz. Serial Data Input. Data must be valid on the falling edge of SCLK. Serial Data Output. Used to clock data from the serial register in readback mode. See Figure 4 and Figure 6. Digital Supply. The voltage range is from 2.7 V to 5.5 V. Digital Ground. Load DAC, Active Low Input. This is used to update the DAC register and consequently the DAC outputs. When tied permanently low, the addressed DAC data register is updated on the rising edge of SYNC. If LDAC is held high during the write cycle, the DAC input register is updated, but the DAC output update only takes place at the falling edge of LDAC (see Figure 3). Using this mode, all analog outputs can be updated simultaneously. The LDAC pin must not be left unconnected. Active High, Edge Sensitive Input. Asserting this pin sets the output current and voltage to the preprogrammed clear code bit setting. Only channels enabled to be cleared are cleared. See the Device Features section for more information. When CLEAR is active, the DAC output register cannot be written to. Rev. F | Page 13 of 51 AD5755-1 Pin No. 15 Mnemonic ALERT 16 FAULT 17 POC 18 19 20 RESET AVDD COMPLV_A 21 CHARTA 22 23 +VSENSE_A COMPDCDC_A 24 VBOOST_A 25 26 27 28 VOUT_A IOUT_A AVSS COMPLV_B 29 CHARTB 30 31 32 +VSENSE_B VOUT_B COMPDCDC_B 33 34 IOUT_B VBOOST_B 35 36 AGND SWB 37 38 39 GNDSWB GNDSWA SWA 40 AVSS 41 SWD 42 43 GNDSWD GNDSWC Data Sheet Description Active High Output. This pin is asserted when there has been no SPI activity on the interface pins for a predetermined time. See the Device Features section for more information. Active Low Output. This pin is asserted low when an open circuit in current mode is detected, a short circuit in voltage mode is detected, a PEC error is detected, or an overtemperature is detected (see the Device Features section). Open-drain output. Power-On Condition. This pin determines the power-on condition and is read during power-on or, alternatively, after a device reset. If POC = 0, the device is powered up with the voltage and current channels in tristate mode. If POC = 1, the device is powered up with a 30 kΩ pull-down resistor to ground on the voltage output channel, and the current channel is in tristate mode. Hardware Reset, Active Low Input. Positive Analog Supply. The voltage range is from 9 V to 33 V. Optional Compensation Capacitor Connection for VOUT_A Output Buffer. Connecting a 220 pF capacitor between this pin and the VOUT_A pin allows the voltage output to drive up to 2 µF. Note that the addition of this capacitor reduces the bandwidth of the output amplifier, increasing the settling time. HART Input Connection for DAC Channel A. For more information, see the HART Connectivity section. If unused, leave as an open circuit. Sense Connection for the Positive Voltage Output Load Connection for VOUT_A. DC-to-DC Compensation Capacitor. Connect a 10 nF capacitor from this pin to ground. Used to regulate the feedback loop of the Channel A dc-to-dc converter. Alternatively, if using an external compensation resistor, place a resistor in series with a capacitor to ground from this pin (see the DC-to-DC Converter Compensation Capacitors and the AICC Supply Requirements—Slewing sections in the Device Features section for more information). Supply for Channel A Current Output Stage (see Figure 74). This is also the supply for the VOUT_x stage, which is regulated to 15 V by the dc-to-dc converter. To use the dc-to-dc feature of the device, connect as shown in Figure 81. Buffered Analog Output Voltage for DAC Channel A. Current Output Pin for DAC Channel A. Negative Analog Supply. Voltage range is from 0 V to −26.4 V. Optional Compensation Capacitor Connection for VOUT_B Output Buffer. Connecting a 220 pF capacitor between this pin and the VOUT_B pin allows the voltage output to drive up to 2 µF. Note that the addition of this capacitor reduces the bandwidth of the output amplifier, increasing the settling time. HART Input Connection for DAC Channel B. For more information, see the HART Connectivity section. If unused, leave as an open circuit. Sense Connection for the Positive Voltage Output Load Connection for VOUT_B. Buffered Analog Output Voltage for DAC Channel B. DC-to-DC Compensation Capacitor. Connect a 10 nF capacitor from this pin to ground. Used to regulate the feedback loop of the Channel B dc-to-dc converter. Alternatively, if using an external compensation resistor, place a resistor in series with a capacitor to ground from this pin (see the DC-to-DC Converter Compensation Capacitors and AICC Supply Requirements—Slewing sections in the Device Features section for more information). Current Output Pin for DAC Channel B. Supply for Channel B Current Output Stage (see Figure 74). This is also the supply for the VOUT_x stage, which is regulated to 15 V by the dc-to-dc converter. To use the dc-to-dc feature of the device, connect as shown in Figure 81. Ground Reference Point for Analog Circuitry. This must be connected to 0 V. Switching Output for Channel B DC-to-DC Circuitry. To use the dc-to-dc feature of the device, connect as shown in Figure 81. Ground Connection for DC-to-DC Switching Circuit. This pin must always be connected to ground. Ground Connection for DC-to-DC Switching Circuit. This pin must always be connected to ground. Switching Output for Channel A DC-to-DC Circuitry. To use the dc-to-dc feature of the device, connect as shown in Figure 81. Negative Analog Supply Pin. The voltage range is from −10.8 V to −26.4 V. This pin can be connected to 0 V if using the device in unipolar supply mode. Switching Output for Channel D DC-DC Circuitry. To use the dc-to-dc feature of the device, connect as shown in Figure 81. Ground Connections for DC-to-DC Switching Circuit. This pin must always be connected to ground. Ground Connections for DC-to-DC Switching Circuit. This pin must always be connected to ground. Rev. F | Page 14 of 51 Data Sheet Pin No. 44 Mnemonic SWC 45 46 AVCC VBOOST_C 47 48 IOUT_C COMPDCDC_C 49 50 51 VOUT_C +VSENSE_C CHARTC 52 COMPLV_C 53 54 55 56 AVSS IOUT_D VOUT_D VBOOST_D 57 COMPDCDC_D 58 59 +VSENSE_D CHARTD 60 COMPLV_D 61 62 REFIN REFOUT 63 RSET_D 64 RSET_C EPAD AD5755-1 Description Switching Output for Channel C DC-to-DC Circuitry. To use the dc-to-dc feature of the device, connect as shown in Figure 81. Supply for DC-to-DC Circuitry. Supply for Channel C Current Output Stage (see Figure 74). This is also the supply for the VOUT_x stage, which is regulated to 15 V by the dc-to-dc converter. To use the dc-to-dc feature of the device, connect as shown in Figure 81. Current Output Pin for DAC Channel C. DC-to-DC Compensation Capacitor. Connect a 10 nF capacitor from this pin to ground. Used to regulate the feedback loop of the Channel C dc-to-dc converter. Alternatively, if using an external compensation resistor, place a resistor in series with a capacitor to ground from this pin (see the DC-to-DC Converter Compensation Capacitors and AICC Supply Requirements—Slewing sections in the Device Features section for more information). Buffered Analog Output Voltage for DAC Channel C. Sense Connection for the Positive Voltage Output Load Connection for VOUT_C. HART Input Connection for DAC Channel C. For more information, see the HART Connectivity section. If unused, leave as an open circuit. Optional Compensation Capacitor Connection for VOUT_C Output Buffer. Connecting a 220 pF capacitor between this pin and the VOUT_C pin allows the voltage output to drive up to 2 µF. Note that the addition of this capacitor reduces the bandwidth of the output amplifier, increasing the settling time. Negative Analog Supply Pin. Current Output Pin for DAC Channel D. Buffered Analog Output Voltage for DAC Channel D. Supply for Channel D Current Output Stage (see Figure 74). This is also the supply for the VOUT_x stage, which is regulated to 15 V by the dc-to-dc converter. To use the dc-to-dc feature of the device, connect as shown in Figure 81. DC-to-DC Compensation Capacitor. Connect a 10 nF capacitor from this pin to ground. Used to regulate the feedback loop of the Channel D dc-to-dc converter. Alternatively, if using an external compensation resistor, place a resistor in series with a capacitor to ground from this pin (see the DC-to-DC Converter Compensation Capacitors and AICC Supply Requirements—Slewing sections in the Device Features section for more information). Sense Connection for the Positive Voltage Output Load Connection for VOUT_D. HART Input Connection for DAC Channel D. For more information, see the HART Connectivity section. If unused, leave as an open circuit. Optional Compensation Capacitor Connection for VOUT_D Output Buffer. Connecting a 220 pF capacitor between this pin and the VOUT_D pin allows the voltage output to drive up to 2 µF. Note that the addition of this capacitor reduces the bandwidth of the output amplifier, increasing the settling time. External Reference Voltage Input. Internal Reference Voltage Output. Place a 0.1 µF capacitor between REFOUT and REFGND. REFOUT must be connected to REFIN to use the internal reference. An external, precision, low drift 15 kΩ current setting resistor can be connected to this pin to improve the IOUT_D temperature drift performance. See the Device Features section. An external, precision, low drift 15 kΩ current setting resistor can be connected to this pin to improve the IOUT_C temperature drift performance. See the Device Features section. Exposed Pad. Connect this exposed pad to the potential of the AVSS pin, or, alternatively, leave it electrically unconnected. It is recommended that the pad be thermally connected to a copper plane for enhanced thermal performance. Rev. F | Page 15 of 51 AD5755-1 Data Sheet TYPICAL PERFORMANCE CHARACTERISTICS VOLTAGE OUTPUTS 0.0015 0.0015 ±10V RANGE AVDD = +15V ±5V RANGE AVSS = –15V +10V RANGE TA = 25°C +5V RANGE +10V RANGE WITH DCDC 0.0010 INL ERROR (%FSR) 0.0005 0 –0.0005 0.0005 0 10k 20k 30k 40k 50k 60k CODE 09226-127 –20 0 20 40 60 80 100 TEMPERATURE (°C) Figure 12. Integral Nonlinearity Error vs. Temperature Figure 9. Integral Nonlinearity Error vs. DAC Code 1.0 1.0 ±10V RANGE AVDD = +15V ±5V RANGE AVSS = –15V +10V RANGE TA = 25°C +5V RANGE +10V RANGE WITH DCDC 0.8 0.6 AVDD = +15V AVSS = –15V ALL RANGES 0.8 0.6 DNL ERROR (LSB) 0.4 0.2 0 –0.2 –0.4 0.4 0.2 DNL ERROR MAX DNL ERROR MIN 0 –0.2 –0.6 –0.8 –0.8 –1.0 0 10k 20k 30k 40k 50k 60k CODE –1.0 –40 Figure 10. Differential Nonlinearity Error vs. DAC Code –20 0 60 40 20 TEMPERATURE (°C) 80 100 09226-128 –0.4 –0.6 09226-024 DNL ERROR (LSB) AVDD = +15V AVSS = –15V OUTPUT UNLOADED –0.0005 –0.0015 –40 09226-023 0 Figure 13. Differential Nonlinearity Error vs. Temperature 0.012 0.006 TOTAL UNADJUSTED ERROR (%FSR) ±10V RANGE AVDD = +15V ±5V RANGE AVSS = –15V +10V RANGE TA = 25°C +5V RANGE +10V RANGE WITH DCDC 0.004 0.002 0 –0.002 –0.004 –0.006 –0.008 0 10k 20k 30k 40k 50k 60k CODE 09226-025 TOTAL UNADJUSTED ERROR (%FSR) +10V RANGE MAX INL ±10V RANGE MAX INL +10V RANGE MIN INL ±10V RANGE MIN INL –0.0010 –0.0010 –0.010 +5V RANGE MAX INL ±5V RANGE MAX INL +5V RANGE MIN INL ±5V RANGE MIN INL +5V RANGE +10V RANGE ±5V RANGE ±10V RANGE 0.010 0.008 AVDD = +15V AVSS = –15V OUTPUT UNLOADED 0.006 0.004 0.002 0 –0.002 09226-129 INL ERROR (%FSR) 0.0010 –0.004 –0.006 –40 –20 0 20 40 60 80 TEMPERATURE (°C) Figure 14. Total Unadjusted Error vs. Temperature Figure 11. Total Unadjusted Error vs. DAC Code Rev. F | Page 16 of 51 100 Data Sheet AD5755-1 0.0025 0.0020 –0.010 +5V RANGE +12V RANGE AVDD = +15V AVSS = 0V OUTPUT UNLOADED –0.015 –0.020 –0.025 –0.030 –20 20 0 40 80 60 0.0010 0.0005 0 ±5V RANGE ±10V RANGE –0.0005 –0.0010 AVDD = +15V AVSS = –15V OUTPUT UNLOADED –0.0015 –0.0020 –40 100 –20 0 TEMPERATURE (°C) Figure 15. Total Unadjusted Error vs. Temperature, Single Supply GAIN ERROR (%FSR) 0.004 0.002 0 100 AVDD = +15V AVSS = –15V OUTPUT UNLOADED 0.004 0.002 0 –0.002 –0.002 –20 0 20 40 60 80 –0.006 –40 100 09226-135 –0.004 09226-132 FULL-SCALE ERROR (%FSR) 0.006 AVDD = +15V AVSS = –15V OUTPUT UNLOADED 0.006 –0.004 –20 0 TEMPERATURE (°C) 0.0010 0.0010 ZERO-SCALE ERROR (%FSR) 0.0015 0.0005 0 –0.0005 +5V RANGE +10V RANGE AVDD = +15V AVSS = –15V OUTPUT UNLOADED 09226-133 –0.0020 –20 0 20 40 40 60 80 100 80 100 Figure 19. Gain Error vs. Temperature 0.0015 –0.0010 20 TEMPERATURE (°C) Figure 16. Full-Scale Error vs. Temperature OFFSET (%FSR) 80 +5V RANGE +10V RANGE ±5V RANGE ±10V RANGE 0.008 0.008 –0.0025 –40 60 0.010 +5V RANGE +10V RANGE ±5V RANGE ±10V RANGE 0.010 –0.0015 40 Figure 18. Bipolar Zero Error vs. Temperature 0.012 –0.006 –40 20 TEMPERATURE (°C) 60 80 100 0.0005 0 –0.0005 –0.0010 –0.0015 –0.0020 –40 +5V RANGE +10V RANGE ±5V RANGE ±10V RANGE AVDD = +15V AVSS = –15V OUTPUT UNLOADED –20 0 09226-136 –0.035 –40 0.0015 09226-134 BIPOLAR ZERO ERROR (%FSR) –0.005 09226-130 TOTAL UNADJUSTED ERROR (%FSR) 0 20 40 60 TEMPERATURE (°C) TEMPERATURE (°C) Figure 20. Zero-Scale Error vs. Temperature Figure 17. Offset Error vs. Temperature Rev. F | Page 17 of 51 AD5755-1 Data Sheet 0.0020 0.0015 0.0015 OUTPUT VOLTAGE DELTA (V) 0.0020 0.0005 0V TO 10V RANGE MAX INL 0V TO 10V RANGE MIN INL TA = 25°C AVSS = –26.4V FOR AVDD > +26.4V 0 –0.0005 –0.0010 0.0010 0.0005 0 –0.0005 –0.0010 –0.0015 –0.0015 10 15 25 20 –0.0020 –20 09226-034 –0.0020 30 SUPPLY (V) 8 OUTPUT VOLTAGE (V) 0.4 0.2 DNL ERROR MAX DNL ERROR MIN 0 –8 –4 0 4 8 12 16 20 12 AVDD = +15V AVSS = –15V ALL RANGES TA = 25°C AVSS = –26.4V FOR AVDD > +26.4V 0.6 –12 Figure 24. Source and Sink Capability of Output Amplifier 1.0 0.8 –16 OUTPUT CURRENT (mA) Figure 21. Integral Nonlinearity Error vs. AVDD/|AVSS| DNL ERROR (LSB) AVDD = +15V AVSS = –15V ±10V RANGE TA = 25°C 09226-036 INL ERROR (%FSR) 0.0010 8mA LIMIT, CODE = 0xFFFF 16mA LIMIT, CODE = 0xFFFF –0.2 –0.4 AVDD = +15V AVSS = –15V ±10V RANGE TA = 25°C OUTPUT UNLOADED 4 0 –4 –0.6 –8 15 20 25 30 SUPPLY (V) –12 –5 5 10 15 TIME (µs) Figure 22. Differential Nonlinearity Error vs. AVDD/|AVSS| Figure 25. Full-Scale Positive Step 0.008 12 0V TO 10V RANGE MAX TUE 0V TO 10V RANGE MIN TUE TA = 25°C AVSS = –26.4V FOR AVDD > +26.4V AVDD = +15V AVSS = –15V ±10V RANGE TA = 25°C OUTPUT UNLOADED 8 OUTPUT VOLTAGE (V) 0.006 0.004 0.002 0 –0.008 4 0 –4 –0.004 10 15 20 25 30 SUPPLY (V) Figure 23. Total Unadjusted Error vs. AVDD/|AVSS| –12 –5 0 5 10 TIME (µs) Figure 26. Full-Scale Negative Step Rev. F | Page 18 of 51 15 09226-038 –8 09226-035 TOTAL UNADJUSTED ERROR (%FSR) 0 09226-037 –1.0 10 09226-138 –0.8 Data Sheet AD5755-1 20 15 OUTPUT VOLTAGE (mV) 10 5 0 –5 –10 10 5 0 –5 –10 –15 AVDD = +15V AVSS = –15V TA = 25°C –15 –20 THE EXTERNAL RESISTOR IS A VISHAY S102C, 0.6ppm RESISTOR 0 1 2 3 4 5 TIME (µs) –25 09226-039 –20 0 50 75 100 Figure 30. VOUT_x vs. Time on Power-Up 60 AVDD = +15V AVSS = –15V ±10V RANGE TA = 25°C OUTPUT UNLOADED 40 20 OUTPUT VOLTAGE (mV) 10 5 0 –5 0 –20 –40 –60 POC = 1 POC = 0 –80 AVDD = +15V AVSS = –15V ±10V RANGE TA = 25°C INT_ENABLE = 1 –100 –10 –120 0 1 2 3 4 5 6 7 8 9 10 TIME (s) –140 09226-040 –15 0 AVDD = +15V AVSS = –15V 4 6 8 10 TIME (µs) Figure 31. VOUT_x vs. Time on Output Enable Figure 28. Peak-to-Peak Noise (0.1 Hz to 10 Hz Bandwidth) 300 2 09226-044 15 0 ±10V RANGE OUTPUT UNLOADED TA = 25°C –20 VOUT_x PSRR (dB) 200 100 0 –100 AVDD = +15V VBOOST = +15V AVSS = –15V TA = 25°C –40 –60 –80 –100 –200 –300 0 1 2 3 4 5 6 7 8 9 TIME (µs) 10 09226-041 OUTPUT VOLTAGE (µV) 125 TIME (µs) Figure 27. Digital-to-Analog Glitch OUTPUT VOLTAGE (µV) 25 –120 10 100 1k 10k 100k FREQUENCY (Hz) Figure 32. VOUT_x PSRR vs. Frequency Figure 29. Peak-to-Peak Noise (100 kHz Bandwidth) Rev. F | Page 19 of 51 1M 10M 09226-045 OUTPUT VOLTAGE (V) 25 AV DD = +15V AV SS = –15V ±10V RANGE TA = 25°C 0x7FFF TO 0x8000 0x8000 TO 0x7FFF 09226-043 15 AD5755-1 Data Sheet CURRENT OUTPUTS 0.0010 0.0025 AVDD = +15V AVSS = –15V TA = 25°C 0.0008 0.0006 INL ERROR (%FSR) 0.0005 –0.0005 4mA TO 4mA TO 4mA TO 4mA TO 20mA, 20mA, 20mA, 20mA, 10000 20000 30000 40000 50000 4mA TO 0mA TO 0mA TO 0mA TO 4mA TO 0mA TO 0.0002 0 –0.0002 20mA RANGE MAX INL 24mA RANGE MAX INL 20mA RANGE MIN INL 20mA RANGE MAX INL 20mA RANGE MAX INL 24mA RANGE MIN INL –0.0004 –0.0008 –0.0010 –40 60000 –20 0 40 60 80 100 Figure 36. Integral Nonlinearity vs. Temperature, Internal RSET Figure 33. Integral Nonlinearity vs. Code 0.0020 1.0 AVDD = +15V AVSS = –15V TA = 25°C 0.8 4mA TO 20mA RANGE MAX INL 0mA TO 24mA RANGE MAX INL 0mA TO 20mA RANGE MIN INL 0.0015 0.6 0.0010 0.4 INL ERROR (%FSR) 0.2 0 –0.2 –0.4 0.0005 0mA TO 20mA RANGE MAX INL 4mA TO 20mA RANGE MIN INL 0mA TO 24mA RANGE MIN INL 0 –0.0005 –0.0010 –0.6 –1.0 0 10000 EXTERNAL RSET EXTERNAL RSET, WITH DC-TO-DC CONVERTER INTERNAL RSET INTERNAL RSET, WITH DC-TO-DC CONVERTER 20000 30000 40000 50000 AVDD = +15V AVSS = –15V/0V –0.0015 –0.0020 –40 60000 –20 0 20 40 09226-153 20mA, 20mA, 20mA, 20mA, 09226-150 4mA TO 4mA TO 4mA TO 4mA TO –0.8 60 80 100 TEMPERATURE (°C) CODE Figure 37. Integral Nonlinearity vs. Temperature, External RSET Figure 34. Differential Nonlinearity vs. Code 1.0 0.035 AVDD = +15V AVSS = –15V/0V ALL RANGES INTERNAL AND EXTERNAL RSET 0.8 0.030 0.6 0.025 0.015 DNL ERROR (LSB) AVDD = +15V AVSS = –15V TA = 25°C ALL CHANNELS ENABLED 0.020 0.010 4mA TO 4mA TO 4mA TO 4mA TO 0.005 0 20mA, 20mA, 20mA, 20mA, EXTERNAL R SET EXTERNAL R SET, WITH DC-TO-DC CONVERTER INTERNAL RSET INTERNAL RSET, WITH DC-TO-DC CONVERTER 0.4 0.2 DNL ERROR MAX DNL ERROR MIN 0 –0.2 –0.4 –0.6 09226-151 –0.005 –0.010 –0.015 0 10000 20000 30000 40000 50000 60000 CODE –0.8 –1.0 –40 –20 0 20 40 60 TEMPERATURE (°C) 80 Figure 38. Differential Nonlinearity vs. Temperature Figure 35. Total Unadjusted Error vs. Code Rev. F | Page 20 of 51 100 09226-154 DNL ERROR (LSB) 20 TEMPERATURE (°C) CODE TOTAL UNADJUSTED ERROR (%FSR) AVDD = +15V AVSS = –15V/0V –0.0006 EXTERNAL RSET EXTERNAL RSET, WITH DC-TO-DC CONVERTER INTERNAL RSET INTERNAL RSET, WITH DC-TO-DC CONVERTER –0.0025 0 0.0004 09226-152 –0.0015 09226-149 INL ERROR (%FSR) 0.0015 Data Sheet AD5755-1 0.03 0.02 0.01 0.01 0 –0.01 AVDD = +15V AVSS = –15V/0V –0.02 –0.03 4mA TO 0mA TO 0mA TO 4mA TO 0mA TO 0mA TO –0.04 –0.05 –0.06 –0.07 –20 0 60 40 20 TEMPERATURE (°C) –0.02 AVDD = +15V AVSS = –15V/0V –0.03 4mA TO 0mA TO 0mA TO 4mA TO 0mA TO 0mA TO –0.04 80 –0.05 –0.06 –40 100 Figure 39. Total Unadjusted Error vs. Temperature 20 40 60 TEMPERATURE (°C) 80 100 0.0025 0.02 0.0020 0.01 0.0015 INL ERROR (%FSR) 0 –0.01 –0.02 AVDD = +15V AVSS = –15V/0V –0.03 4mA TO 0mA TO 0mA TO 4mA TO 0mA TO 0mA TO –0.04 –0.05 –0.06 –0.07 –20 0 20mA INTERNAL RSET 20mA INTERNAL RSET 24mA INTERNAL RSET 20mA EXTERNAL RSET 20mA EXTERNAL RSET 24mA EXTERNAL RSET 20 40 60 TEMPERATURE (°C) 4mA TO 20mA RANGE MAX INL 4mA TO 20mA RANGE MIN INL TA = 25°C AVSS = –26.4V FOR AVDD > +26.4V 0.0010 0.0005 0 –0.0005 –0.0010 09226-157 FULL-SCALE ERROR (%FSR) 0 Figure 42. Gain Error vs. Temperature 0.03 –0.08 –40 –20 20mA INTERNAL RSET 20mA INTERNAL RSET 24mA INTERNAL RSET 20mA EXTERNAL RSET 20mA EXTERNAL RSET 24mA EXTERNAL RSET 80 –0.0015 –0.0020 10 100 Figure 40. Full Scale Error vs. Temperature 15 20 SUPPLY (V) 25 30 09226-056 –0.08 –40 20mA INTERNAL RSET 20mA INTERNAL RSET 24mA INTERNAL RSET 20mA EXTERNAL RSET 20mA EXTERNAL RSET 24mA EXTERNAL RSET –0.01 09226-159 GAIN ERROR (%FSR) 0 09226-155 TOTAL UNADJSUTED ERROR (%FSR) 0.02 Figure 43. Integral Nonlinearity Error vs. AVDD/|AVSS|, Over Supply, External RSET 0.020 0.0015 0.015 0.0005 0 AVDD = +15V AVSS = –15V/0V –0.005 4mA TO 0mA TO 0mA TO 4mA TO 0mA TO 0mA TO –0.010 –0.015 –0.020 –40 –20 0 20mA INTERNAL RSET 20mA INTERNAL RSET 24mA INTERNAL RSET 20mA EXTERNAL RSET 20mA EXTERNAL RSET 24mA EXTERNAL RSET 60 40 20 TEMPERATURE (°C) 80 0 –0.0005 –0.0010 –0.0015 100 –0.0020 –0.0025 10 Figure 41. Offset Error vs. Temperature 4mA TO 20mA RANGE MAX INL 4mA TO 20mA RANGE MIN INL TA = 25°C AVSS = –26.4V FOR AVDD > +26.4V 15 20 SUPPLY (V) 25 30 Figure 44. Integral Nonlinearity Error vs. AVDD/|AVSS|, Over Supply, Internal RSET Rev. F | Page 21 of 51 09226-057 INL ERROR (%FSR) 0.005 09226-158 OFFSET ERROR (%FSR) 0.0010 0.010 AD5755-1 Data Sheet 1.0 6 ALL RANGES INTERNAL AND EXTERNAL R SET TA = 25°C AVSS = –26.4V FOR AVDD > +26.4V 0.8 5 0.4 4 CURRENT (µA) DNL ERROR (LSB) 0.6 AVDD = +15V AVSS = –15V TA = 25°C RLOAD = 300Ω 0.2 DNL ERROR MAX DNL ERROR MIN 0 –0.2 3 2 –0.4 –0.6 1 –0.8 20 25 30 SUPPLY (V) 0 10 15 20 TIME (µs) Figure 48. Output Current vs. Time on Power-Up Figure 45. Differential Nonlinearity Error vs. AVDD 4 0.012 2 0.010 0 0.006 0.004 0.002 0 10 –2 –4 –6 4mA TO 20mA RANGE MAX TUE 4mA TO 20mA RANGE MIN TUE TA = 25°C AVSS = –26.4V FOR AVDD > +26.4V 15 20 SUPPLY (V) AVDD = +15V AVSS = –15V TA = 25°C RLOAD = 300Ω INT_EN = 1 –8 25 30 –10 0 1 2 3 4 5 6 TIME (µs) 09226-063 CURRENT (µA) 0.008 09226-060 TOTAL UNADJUSTED ERROR (%FSR) 5 0 09226-062 15 09226-162 –1.0 10 Figure 49. Output Current vs. Time on Output Enable Figure 46. Total Unadjusted Error vs. AVDD, External RSET 30 0 25 –0.006 –0.008 –0.010 4mA TO 20mA RANGE MAX TUE 4mA TO 20mA RANGE MIN TUE TA = 25°C AVSS = –26.4V FOR AVDD > +26.4V –0.012 –0.014 –0.016 20 IOUT VBOOST 15 10 0mA TO 24mA RANGE 1kΩ LOAD fSW = 410kHz INDUCTOR = 10µH (XAL4040-103) AVCC = 5V TA = 25°C 5 –0.018 –0.020 10 15 20 SUPPLY (V) 25 30 0 –0.50 –0.25 0 0.25 0.50 0.75 1.00 1.25 09226-167 OUTPUT CURRENT (mA) –0.004 09226-061 TOTAL UNADJUSTED ERROR (%FSR) –0.002 1.50 1.75 2.00 TIME (ms) Figure 50. Output Current and VBOOST_x Settling Time with DC-to-DC Converter (See Figure 81) Figure 47. Total Unadjusted Error vs. AVDD, Internal RSET Rev. F | Page 22 of 51 Data Sheet AD5755-1 8 30 0mA TO 24mA RANGE 1kΩ LOAD FSW = 410kHz INDUCTOR = 10µH (XAL4040-103) TA = 25°C 7 HEADROOM VOLTAGE (V) 20 TA = –40°C TA = +25°C TA = +105°C 10 0mA TO 24mA RANGE 1kΩ LOAD fSW = 410kHz INDUCTOR = 10µH (XAL4040-103) AVCC = 5V 5 0 –0.25 0 0.25 0.50 0.75 1.00 1.25 1.50 6 5 4 3 2 1 0 0 1.75 5 10 Figure 51. Output Current Settling with DC-to-DC Converter vs. Time and Temperature (See Figure 81) 0 –20 20 –40 IOUT_x PSRR (dB) 25 IOUT, AVCC = 4.5V IOUT, AVCC = 5.0V IOUT, AVCC = 5.5V 10 0mA TO 24mA RANGE 1kΩ LOAD fSW = 410kHz INDUCTOR = 10µH (XAL4040-103) TA = 25°C 5 0 –0.25 0 0.25 0.50 0.75 1.00 1.25 1.50 20mA OUTPUT 10mA OUTPUT 6 4 2 0 –2 –4 AVDD = 5V fSW = 410kHz INDUCTOR = 10µH (XAL4040-103) 2 4 6 8 10 0mA TO 24mA RANGE 1kΩ LOAD EXTERNAL R SET TA = 25°C 12 09226-170 –6 0 100 1k 10k 100k FREQUENCY (Hz) 8 –10 –80 –120 10 1.75 Figure 52. Output Current Settling with DC-to-DC Converter vs. Time and AVCC (See Figure 81) –8 –60 –100 TIME (ms) 10 AVDD = +15V VBOOST = +15V AVSS = –15V TA = 25°C 14 TIME (µs) Figure 53. Output Current vs. Time with DC-to-DC Converter (See Figure 81) Rev. F | Page 23 of 51 Figure 55. IOUT_x PSRR vs. Frequency 1M 10M 09226-068 15 09226-169 OUTPUT CURRENT (mA) 20 Figure 54. DC-to-DC Converter Headroom vs. Output Current (See Figure 81) 30 CURRENT (AC-COUPLED) (µA) 15 CURRENT (mA) TIME (ms) 09226-067 IOUT, IOUT, IOUT, 15 09226-168 OUTPUT CURRENT (mA) 25 AD5755-1 Data Sheet DC-TO-DC BLOCK 100 100 AVDD = 4.5V AVDD = 5.0V AVDD = 5.5V 90 90 80 70 60 50 40 30 0mA TO 24mA RANGE 1kΩ LOAD EXTERNAL RSET fSW = 410kHz INDUCTOR = 10µH (XAL4040-103) TA = 25°C 10 0 0 0.005 0.010 0.025 0.020 0.015 OUTPUT CURRENT (A) 20mA 60 50 40 30 0mA TO 24mA RANGE 1kΩ LOAD EXTERNAL RSET AVDD = 5V fSW = 410kHz INDUCTOR = 10µH (XAL4040-103) 20 10 0 –40 09226-255 20 70 –20 20 0 40 60 80 100 120 140 TEMPERATURE (°C) Figure 56. Efficiency at VBOOST_x vs. Output Current (See Figure 81) Figure 59. Output Efficiency vs. Temperature (See Figure 81) 100 0.6 09226-258 OUTPUT EFFICIENCY (%) VBOOST EFFICIENCY (%) 80 90 SWITCH RESISTANCE (Ω) 70 60 50 40 0mA TO 24mA RANGE 1kΩ LOAD EXTERNAL RSET AVDD = 5V fSW = 410kHz INDUCTOR = 10µH (XAL4040-103) 20 10 0 -40 -20 0 20 40 60 80 100 120 140 TEMPERATURE (°C) AVDD = 4.5V AVDD = 5.0V AVDD = 5.5V 70 60 50 40 0mA TO 24mA RANGE 1kΩ LOAD EXTERNAL RSET fSW = 410kHz INDUCTOR = 10µH (XAL4040-103) TA = 25°C 10 0 0 0.005 0.010 0.015 0.020 0.025 OUTPUT CURRENT (A) 09226-257 OUTPUT EFFICIENCY (%) 80 20 0.2 0 –40 –20 0 20 40 60 80 TEMPERATURE (°C) Figure 60. Switch Resistance vs. Temperature 100 30 0.3 0.1 Figure 57. Efficiency at VBOOST_x vs. Temperature (See Figure 81) 90 0.4 Figure 58. Output Efficiency vs. Output Current (See Figure 81) Rev. F | Page 24 of 51 100 09226-123 30 09226-256 VBOOST EFFICIENCY (%) 0.5 20mA 80 Data Sheet AD5755-1 REFERENCE 5.0050 16 AVDD REFOUT TA = 25°C 14 5.0040 12 5.0035 REFOUT (V) 8 6 4 5.0025 5.0020 5.0015 2 5.0010 0 5.0005 0 0.2 0.4 0.6 0.8 1.0 1.2 TIME (ms) 5.0000 –40 09226-010 –2 Figure 61. REFOUT Turn-On Transient –20 0 20 40 60 80 100 TEMPERATURE (°C) Figure 64. REFOUT vs. Temperature (When the AD5575-1 is soldered onto a PCB, the reference shifts due to thermal shock on the package. The average output voltage shift is −4 mV. Measurement of these parts after seven days shows that the outputs typically shift back 2 mV toward their initial values. This second shift is due to the relaxations of stress incurred during soldering.) 4 REFERENCE OUTPUT VOLTAGE (µV) 5.0030 09226-163 VOLTAGE (V) 10 AVDD = 15V TA = 25°C 3 30 DEVICES SHOWN AVDD = 15V 5.0045 5.002 2 AVDD = 15V TA = 25°C 5.001 1 5.000 REFOUT (V) 0 –1 4.999 4.998 –2 2 0 4 6 8 10 TIME (s) 4.996 4.995 Figure 62. REFOUT Output Noise (0.1 Hz to 10 Hz Bandwidth) 0 2 4 6 8 10 LOAD CURRENT (mA) 09226-014 –3 09226-011 4.997 Figure 65. REFOUT vs. Load Current AVDD = 15V TA = 25°C 100 0 –50 –100 –150 0 5 10 15 TIME (ms) Figure 63. REFOUT Output Noise (100 kHz Bandwidth) 20 4.99995 TA = 25°C 4.99990 4.99985 4.99980 4.99975 4.99970 4.99965 4.99960 10 15 20 25 AVDD (V) Figure 66. REFOUT vs. Supply Rev. F | Page 25 of 51 30 09226-015 50 REFERENCE OUTPUT VOLTAGE (V) 5.00000 09226-012 REFERENCE OUTPUT VOLTAGE (µV) 150 AD5755-1 Data Sheet GENERAL 13.4 450 DVDD = 5V TA = 25°C 400 13.3 350 FREQUENCY (MHz) 13.2 250 200 150 13.1 13.0 12.9 12.8 100 12.7 50 0 1 2 3 4 5 SDIN VOLTAGE (V) 12.6 –40 09226-007 0 DVDD = 5.5V –20 0 20 40 60 80 09226-020 DICC (µA) 300 100 TEMPERATURE (°C) Figure 67. DICC vs. Logic Input Voltage Figure 70. Internal Oscillator Frequency vs. Temperature 10 14.4 8 14.2 6 AIDD AISS TA = 25°C VOUT = 0V OUTPUT UNLOADED 2 0 14.0 FREQUENCY (MHz) CURRENT (mA) 4 –2 –4 13.8 13.6 13.4 –6 –8 15 20 25 30 VOLTAGE (V) 09226-008 –12 10 Figure 68. AIDD/AISS vs. AVDD/|AVSS| 7 5 4 3 2 AIDD TA = 25°C IOUT = 0mA 15 20 25 VOLTAGE (V) 30 09226-009 CURRENT (mA) 6 0 10 3.0 3.5 4.0 4.5 5.0 5.5 VOLTAGE (V) Figure 71. Internal Oscillator Frequency vs. DVDD Supply Voltage 8 1 13.0 2.5 DVDD = 5.5V TA = 25°C Figure 69. AIDD vs. AVDD Rev. F | Page 26 of 51 09226-021 13.2 –10 Data Sheet AD5755-1 TERMINOLOGY Relative Accuracy or Integral Nonlinearity (INL) For the DAC, relative accuracy, or integral nonlinearity, is a measure of the maximum deviation, in LSBs, from the best fit line through the DAC transfer function. A typical INL vs. code plot is shown in Figure 9. Full-Scale Error Full-scale error is a measure of the output error when full-scale code is loaded to the DAC register. Ideally, the output is fullscale − 1 LSB. Full-scale error is expressed in percent of fullscale range (% FSR). Differential Nonlinearity (DNL) Differential nonlinearity (DNL) 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 is shown in Figure 10. Full-Scale TC Full-scale TC is a measure of the change in full-scale error with changes in temperature and is expressed in ppm FSR/°C. Monotonicity A DAC is monotonic if the output either increases or remains constant for increasing digital input code. The AD5755-1 is monotonic over its full operating temperature range. Negative Full-Scale Error/Zero-Scale Error Negative full-scale error is the error in the DAC output voltage when 0x0000 (straight binary coding) is loaded to the DAC register. Zero-Scale TC This is a measure of the change in zero-scale error with a change in temperature. Zero-scale error TC is expressed in ppm FSR/°C. Bipolar Zero Error Bipolar zero error is the deviation of the analog output from the ideal half-scale output of 0 V when the DAC register is loaded with 0x8000 (straight binary coding). Bipolar Zero TC Bipolar zero TC is a measure of the change in the bipolar zero error with a change in temperature. It is expressed in ppm FSR/°C. Offset Error In voltage output mode, offset error is the deviation of the analog output from the ideal quarter-scale output when in bipolar output ranges and the DAC register is loaded with 0x4000 (straight binary coding). In current output mode, offset error is the deviation of the analog output from the ideal zero-scale output when all DAC registers are loaded with 0x0000. 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 in % FSR. Gain TC This is a measure of the change in gain error with changes in temperature. Gain TC is expressed in ppm FSR/°C. Total Unadjusted Error Total unadjusted error (TUE) is a measure of the output error taking all the various errors into account, including INL error, offset error, gain error, temperature, and time. TUE is expressed in % FSR. DC Crosstalk This 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 while monitoring another DAC, which is at midscale. Current Loop Compliance Voltage The maximum voltage at the IOUT_x pin for which the output current is equal to the programmed value. Voltage Reference Thermal Hysteresis Voltage reference thermal hysteresis is the difference in output voltage measured at +25°C compared to the output voltage measured at +25°C after cycling the temperature from +25°C to −40°C to +105°C and back to +25°C. The hysteresis is expressed in ppm. Output Voltage Settling Time Output voltage settling time is the amount of time it takes for the output to settle to a specified level for a full-scale input change. A plot of settling time is shown in Figure 25, Figure 51, and Figure 52. Slew Rate The slew rate of a device is a limitation in the rate of change of the output voltage. The output slewing speed of a voltage-output digital-to-analog converter is usually limited by the slew rate of the amplifier used at its output. Slew rate is measured from 10% to 90% of the output signal and is given in V/μs. Power-On Glitch Energy Power-on glitch energy is the impulse injected into the analog output when the AD5755-1 is powered-on. It is specified as the area of the glitch in nV-sec. See Figure 30 and Figure 48. 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, but the output voltage remains constant. 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 27. Rev. F | Page 27 of 51 AD5755-1 Data Sheet Glitch Impulse Peak Amplitude Glitch impulse peak amplitude is the peak amplitude of the impulse injected into the analog output when the input code in the DAC register changes state. It is specified as the amplitude of the glitch in mV and is measured when the digital input code is changed by 1 LSB at the major carry transition (~0x7FFF to 0x8000). See Figure 27. 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. 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 a 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 and vice versa) with LDAC low and monitoring the output of another DAC. The energy of the glitch is expressed in nV-sec. Power Supply Rejection Ratio (PSRR) PSRR indicates how the output of the DAC is affected by changes in the power supply voltage. Line Regulation Line regulation is the change in reference output voltage due to a specified change in supply voltage. It is expressed in ppm/V. Load Regulation Load regulation is the change in reference output voltage due to a specified change in load current. It is expressed in ppm/mA. DC-to-DC Converter Headroom This is the difference between the voltage required at the current output and the voltage supplied by the dc-to-dc converter. See Figure 54. Output Efficiency I 2OUT × R LOAD AVCC × AI CC This is defined as the power delivered to a channel’s load vs. the power delivered to the channel’s dc-to-dc input. Efficiency at VBOOST_x I OUT × VBOOST _ x AVCC × AI CC This is defined as the power delivered to a channel’s VBOOST_x supply vs. the power delivered to the dc-to-dc input of the channel. The VBOOST_x quiescent current is considered part of the dc-todc converter’s losses. Reference TC Reference TC is a measure of the change in the reference output voltage with a change in temperature. It is expressed in ppm/°C. Rev. F | Page 28 of 51 Data Sheet AD5755-1 THEORY OF OPERATION The AD5755-1 is a quad, precision digital-to-current loop and voltage output converter designed to meet the requirements of industrial process control applications. It provides a high precision, fully integrated, low cost, single-chip solution for generating current loop and unipolar/bipolar voltage outputs. The current ranges available are 0 mA to 20 mA, 0 mA to 24 mA, and 4 mA to 20 mA. The voltage ranges available are 0 V to 5 V, ±5 V, 0 V to 10 V, and ±10 V. The current and voltage outputs are available on separate pins, and only one is active at any one time. The desired output configuration is user selectable via the DAC control register. The DAC core architecture of the AD5755-1 consists of two matched DAC sections. A simplified circuit diagram is shown in Figure 72. The four MSBs of the 16-bit data-word are decoded to drive 15 switches, E1 to E15. Each of these switches connects one of 15 matched resistors to either ground or the reference buffer output. The remaining 12 bits of the data-word drive Switch S0 to Switch S11 of a 12-bit voltage mode R-2R ladder network. 2R 2R 2R 2R S0 S1 S7/S11 E1 E2 E15 12-BIT R-2R LADDER FOUR MSBs DECODED INTO 15 EQUAL SEGMENTS 09226-069 VOUT 2R Figure 72. DAC Ladder Structure The voltage output from the DAC core is either converted to a current (see Figure 74), which is then mirrored to the supply rail so that the application simply sees a current source output, or it is buffered and scaled to output a software selectable unipolar or bipolar voltage range (see Figure 73). Both the voltage and current outputs are supplied by VBOOST_x. The current and voltage are output on separate pins and cannot be output simultaneously. A channel’s current and voltage output pins can be tied together. +VSENSE_x VOUT_x VOUT_X SHORT FAULT Figure 73. Voltage Output 09226-070 DAC RANGE SCALING R3 T2 A2 T1 IOUT_x A1 RSET 09226-071 16-BIT DAC Voltage Output Amplifier DAC ARCHITECTURE 2R R2 Figure 74. Voltage-to-Current Conversion Circuitry On-chip dynamic power control minimizes package power dissipation in current mode. 2R VBOOST_x The voltage output amplifier is capable of generating both unipolar and bipolar output voltages. It is capable of driving a load of 1 kΩ in parallel with 1 µF (with an external compensation capacitor) to AGND. The source and sink capabilities of the output amplifier are shown in Figure 24. The slew rate is 1.9 V/µs with a full-scale settling time of 16 µs (10 V step). If remote sensing of the load is not required, connect +VSENSE_x directly to VOUT_x. +VSENSE_x must stay within ±3.0 V of VOUT_x for correct operation. Driving Large Capacitive Loads The voltage output amplifier is capable of driving capacitive loads of up to 2 µF with the addition of a 220 pF nonpolarized compensation capacitor on each channel. Take care to choose an appropriate value of compensation capacitor. This capacitor, while allowing the AD5755-1 to drive higher capacitive loads and reduce overshoot, increases the settling time of the part and, therefore, affects the bandwidth of the system. Without the compensation capacitor, up to 10 nF capacitive loads can be driven. See Table 5 for information on connecting compensation capacitors. Reference Buffers The AD5755-1 can operate with either an external or internal reference. The reference input requires a 5 V reference for specified performance. This input voltage is then buffered before it is applied to the DAC. POWER-ON STATE OF THE AD5755-1 On initial power-up of the AD5755-1, the power-on reset circuit powers up in a state that is dependent on the power-on condition (POC) pin. If POC = 0, the voltage output and current output channels power up in tristate mode. If POC = 1, the voltage output channel powers up with a 30 kΩ pull-down resistor to ground, and the current output channel powers up to tristate. Even though the output ranges are not enabled, the default output range is 0 V to 5 V, and the clear code register is loaded Rev. F | Page 29 of 51 AD5755-1 Data Sheet with all zeros. This means that if the user clears the part after power-up, the output is actively driven to 0 V (if the channel has been enabled for clear). OUTPUT I/V AMPLIFIER VREFIN After a device power-on, or a device reset, it is recommended to wait 100 μs or more before writing to the device to allow time for internal calibrations to take place. LDAC SERIAL INTERFACE SCLK SYNC SDIN In this mode, LDAC is held low while data is being clocked into the DAC data register. The addressed DAC output is updated on the rising edge of SYNC. See Table 3 and Figure 3 for timing information. Simultaneous Updating of All DACs In this mode, LDAC is held high while data is being clocked into the DAC data register. Only the first write to each channel’s DAC data register is valid after LDAC is brought high. Any subsequent writes while LDAC is still held high are ignored, though they are loaded into the DAC data register. All the DAC outputs are updated by taking LDAC low after SYNC is taken high. INTERFACE LOGIC SDO 09226-072 DAC DATA REGISTER The input shift register is 24 bits wide. Data is loaded into the device MSB first as a 24-bit word under the control of a serial clock input, SCLK. Data is clocked in on the falling edge of SCLK. Individual DAC Updating DAC REGISTER OFFSET AND GAIN CALIBRATION Input Shift Register There are two ways in which the DAC outputs can be updated: individual updating or simultaneous updating of all DACs. VOUT_x DAC INPUT REGISTER The AD5755-1 is controlled over a versatile 3-wire serial interface that operates at clock rates of up to 30 MHz and is compatible with SPI, QSPI, MICROWIRE, and DSP standards. Data coding is always straight binary. If packet error checking, or PEC (see the Device Features section), is enabled, an additional eight bits must be written to the AD5755-1, creating a 32-bit serial interface. 16-BIT DAC Figure 75. Simplified Serial Interface of Input Loading Circuitry for One DAC Channel TRANSFER FUNCTION Table 6 shows the input code to ideal output voltage relationship for the AD5755-1 for straight binary data coding of the ±10 V output range. Table 6. Ideal Output Voltage to Input Code Relationship Digital Input Straight Binary Data Coding MSB LSB 1111 1111 1111 1111 1111 1111 1111 1110 1000 0000 0000 0000 0000 0000 0000 0001 0000 0000 0000 0000 Rev. F | Page 30 of 51 Analog Output VOUT +2 VREF × (32,767/32,768) +2 VREF × (32,766/32,768) 0V −2 VREF × (32,767/32,768) −2 VREF Data Sheet AD5755-1 REGISTERS Table 7 shows an overview of the registers for the AD5755-1. Table 7. Data, Control, and Readback Registers for the AD5755-1 Register Data DAC Data Register (×4) Gain Register (×4) Offset Register (×4) Clear Code Register (×4) Control Main Control Register Software Register Slew Rate Control Register (×4) DAC Control Register (×4) DC-to-DC Control Register Readback Status Register Description Used to write a DAC code to each DAC channel. AD5755-1 data bits = D15 to D0. There are four DAC data registers, one per DAC channel. Used to program gain trim, on a per channel basis. AD5755-1 data bits = D15 to D0. There are four gain registers, one per DAC channel. Used to program offset trim, on a per channel basis. AD5755-1 data bits = D15 to D0. There are four offset registers, one per DAC channel. Used to program clear code on a per channel basis. AD5755-1 data bits = D15 to D0. There are four clear code registers, one per DAC channel. Used to configure the part for main operation. Sets functions such as status readback during write, enables output on all channels simultaneously, powers on all dc-to-dc converter blocks simultaneously, and enables and sets conditions of the watchdog timer. See the Device Features section for more details. Has three functions. Used to perform a reset, enables the packet error checking feature, and verifies correct data communication operation as part of the watchdog timer feature. Used to program the slew rate of the output. There are four slew rate control registers, one per channel. These registers are used to control the following: Set the output range, for example, 4 mA to 20 mA, 0 V to 10 V. Set whether an internal/external sense resistor is used. Enable/disable a channel for CLEAR. Enable/disable overrange. Enable/disable internal circuitry on a per channel basis. Enable/disable output on a per channel basis. Power on dc-to-dc converters on a per channel basis. There are four DAC control registers, one per DAC channel. Use to set the dc-to-dc control parameters. Can control dc-to-dc maximum voltage, phase, and frequency. This contains any fault information, as well as the status of the packet error checking feature. Rev. F | Page 31 of 51 AD5755-1 Data Sheet PROGRAMMING SEQUENCE TO WRITE/ENABLE THE OUTPUT CORRECTLY CHANGING AND REPROGRAMMING THE RANGE To correctly write to and set up the part from a power-on condition, use the following sequence: 1. 2. 3. 4. 5. Perform a hardware or software reset after initial power-on. The dc-to-dc converter supply block must be configured. Set the dc-to-dc switching frequency, maximum output voltage allowed, and the phase that the four dc-to-dc channels clock at. Configure the DAC control register on a per channel basis. The output range is selected, and the dc-to-dc converter block is enabled (DC_DC bit). Other control bits can be configured at this point. Set the INT_ENABLE bit; however, do not set the output enable bit (OUTEN). Write the required code to the DAC data register. This implements a full DAC calibration internally. Allow at least 200 μs before Step 5 for reduced output glitch. Write to the DAC control register again to enable the output (set the OUTEN bit). When changing between ranges, use the same sequence as described in the Programming Sequence to Write/Enable the Output Correctly section. It is recommended to set the range to its zero point (can be midscale or zero scale) prior to disabling the output. Because the dc-to-dc switching frequency, maximum voltage, and phase have already been selected, there is no need to reprogram these. A flowchart of this sequence is shown in Figure 77. CHANNEL’S OUTPUT IS ENABLED. STEP 1: WRITE TO CHANNEL’S DAC DATA REGISTER. SET THE OUTPUT TO 0V (ZERO OR MIDSCALE). STEP 2: WRITE TO DAC CONTROL REGISTER. DISABLE THE OUTPUT (OUTEN = 0), AND SET THE NEW OUTPUT RANGE. KEEP THE DC_DC BIT AND THE INT_ENABLE BIT SET. STEP 3: WRITE VALUE TO THE DAC DATA REGISTER. STEP 4: WRITE TO DAC CONTROL REGISTER. RELOAD SEQUENCE AS IN STEP 2 ABOVE. THIS TIME SELECT THE OUTEN BIT TO ENABLE THE OUTPUT. POWER ON. Figure 77. Steps for Changing the Output Range STEP 1: PERFORM A SOFTWARE/HARDWARE RESET. STEP 2: WRITE TO DC-TO-DC CONTROL REGISTER TO SET DC-TO-DC CLOCK FREQUENCY, PHASE, AND MAXIMUM VOLTAGE. STEP 3: WRITE TO DAC CONTROL REGISTER. SELECT THE DAC CHANNEL AND OUTPUT RANGE. SET THE DC_DC BIT AND OTHER CONTROL BITS AS REQUIRED. SET THE INT_ENABLE BIT BUT DO NOT SELECT THE OUTEN BIT. STEP 5: WRITE TO DAC CONTROL REGISTER. RELOAD SEQUENCE AS IN STEP 3 ABOVE. THIS TIME SELECT THE OUTEN BIT TO ENABLE THE OUTPUT. 09226-073 STEP 4: WRITE TO EACH/ALL DAC DATA REGISTERS. ALLOW AT LEAST 200µs BETWEEN STEP 3 AND STEP 5 FOR REDUCED OUTPUT GLITCH. Figure 76. Programming Sequence for Enabling the Output Correctly Rev. F | Page 32 of 51 09226-074 A flowchart of this sequence is shown in Figure 76. Data Sheet AD5755-1 DATA REGISTERS The input register is 24 bits wide. When PEC is enabled, the input register is 32 bits wide, with the last eight bits corresponding to the PEC code (see the Packet Error Checking section for more information on PEC). When writing to a data register, the format in Table 8 must be used. DAC Data Register When writing to the AD5755-1 DAC data registers, D15 to D0 are used for DAC data bits. Table 10 shows the register format and Table 9 describes the function of Bit D23 to Bit D16. Table 8. Writing to a Data Register MSB D23 R/W D22 DUT_AD1 D21 DUT_AD0 D20 DREG2 D19 DREG1 D18 DREG0 D17 DAC_AD1 D16 DAC_AD0 LSB D15 to D0 Data Table 9. Input Register Decode Bit R/W Description Indicates a read from or a write to the addressed register. DUT_AD1, DUT_AD0 Used in association with the external pins, AD1 and AD0, to determine which AD5755-1 device is being addressed by the system controller. It is not recommended to tie both AD1 and AD0 low when using PEC, see the Packet Error Checking section. DUT_AD1 DUT_AD0 Function 0 0 Addresses part with Pin AD1 = 0, Pin AD0 = 0 0 1 Addresses part with Pin AD1 = 0, Pin AD0 = 1 1 0 Addresses part with Pin AD1 = 1, Pin AD0 = 0 1 1 Addresses part with Pin AD1 = 1, Pin AD0 = 1 Selects whether a data register or a control register is written to. If a control register is selected, a further decode of CREG bits (see Table 17) is required to select the particular control register, as follows. DREG2 DREG1 DREG0 Function DREG2, DREG1, DREG0 0 0 0 1 1 1 1 DAC_AD1, DAC_AD0 0 1 1 0 0 1 1 0 0 1 0 1 0 1 Write to DAC data register (individual channel write) Write to gain register Write to gain register (all DACs) Write to offset register Write to offset register (all DACs) Write to clear code register Write to a control register These bits are used to decode the DAC channel. DAC_AD1 DAC_AD0 DAC Channel/Register Address 0 0 DAC A 0 1 DAC B 1 0 DAC C 1 1 DAC D X X These are don’t cares if they are not relevant to the operation being performed. Table 10. Programming the DAC Data Registers MSB D23 R/W D22 DUT_AD1 D21 DUT_AD0 D20 DREG2 D19 DREG1 D18 DREG0 Rev. F | Page 33 of 51 D17 DAC_AD1 D16 DAC_AD0 LSB D15 to D0 DAC data AD5755-1 Data Sheet Gain Register in steps of 1 LSB. This is done by setting the DREG[2:0] bits to 100. It is possible to write the same offset code to all four DAC channels at the same time by setting the DREG[2:0] bits to 101. The offset register coding is straight binary as shown in Table 14. The default code in the offset register is 0x8000, which results in zero offset programmed to the output. See the Digital Offset and Gain Control section for more information. The 16-bit gain register, as shown in Table 11, allows the user to adjust the gain of each channel in steps of 1 LSB. This is done by setting the DREG[2:0] bits to 010. It is possible to write the same gain code to all four DAC channels at the same time by setting the DREG[2:0] bits to 011. The gain register coding is straight binary as shown in Table 12. The default code in the gain register is 0xFFFF. In theory, the gain can be tuned across the full range of the output. In practice, the maximum recommended gain trim is about 50% of programmed range to maintain accuracy. See the Digital Offset and Gain Control section for more information. Offset Register The 16-bit offset register, as shown in Table 13, allows the user to adjust the offset of each channel by −32,768 LSBs to +32,768 LSBs Clear Code Register The 16-bit clear code register allows the user to set the clear value of each channel as shown in Table 15. It is possible, via software, to enable or disable on a per channel basis which channels are cleared when the CLEAR pin is activated. The default clear code is 0x0000. See the Asynchronous Clear section for more information. Table 11. Programming the Gain Register R/W 0 DUT_AD1 DUT_AD0 Device address DREG2 0 DREG1 1 DREG0 0 DAC_AD1 DAC_AD0 DAC channel address D15 to D0 Gain adjustment G15 1 1 … 0 0 G14 1 1 … 0 0 G13 1 1 … 0 0 G12 to G4 1 1 … 0 0 DREG2 1 DREG1 0 DREG0 0 DAC_AD1 DAC_AD0 DAC channel address OF14 1 1 1 … 0 … 0 0 OF13 1 1 1 … 0 … 0 0 OF12 to OF4 1 1 1 … 0 … 0 0 OF3 1 1 1 … 0 … 0 0 DREG1 1 DREG0 0 DAC_AD1 DAC_AD0 DAC channel address Table 12. Gain Register Gain Adjustment +65,535 LSBs +65,534 LSBs … 1 LSB 0 LSBs G3 1 1 … 0 0 G2 1 1 … 0 0 G1 1 1 … 0 0 G0 1 0 … 1 0 Table 13. Programming the Offset Register R/W 0 DUT_AD1 DUT_AD0 Device address D15 to D0 Offset adjustment Table 14. Offset Register Options Offset Adjustment +32,768 LSBs +32,767 LSBs +32,766 LSBs … No Adjustment (Default) … −32,767 LSBs −32,768 LSBs OF15 1 1 1 … 1 … 0 0 OF2 1 1 1 … 0 … 0 0 OF1 1 1 0 … 0 … 0 0 OF0 1 0 0 … 0 … 1 0 Table 15. Programming the Clear Code Register R/W 0 DUT_AD1 DUT_AD0 Device address DREG2 1 Rev. F | Page 34 of 51 D15 to D0 Clear code Data Sheet AD5755-1 CONTROL REGISTERS Main Control Register When writing to a control register, use the format shown in Table 16. See Table 9 for information on the configuration of Bit D23 to Bit D16. The control registers are addressed by setting the DREG[2:0] bits to 111 and then setting the CREG[2:0] bits to the appropriate decode address for that register, according to Table 17. These CREG bits select among the various control registers. The main control register options are shown in Table 18 and Table 19. See the Device Features section for more information on the features controlled by the main control register. Table 16. Writing to a Control Register MSB D23 R/W D22 DUT_AD1 D21 DUT_AD0 D20 1 D19 1 D18 1 D17 DAC_AD1 D16 DAC_AD0 D15 CREG2 D14 CREG1 D13 CREG0 LSB D12 to D0 Data Table 17. Register Access Decode CREG2 (D15) 0 0 0 0 1 CREG1 (D14) 0 0 1 1 0 CREG0 (D13) 0 1 0 1 0 Function Slew rate control register (one per channel) Main control register DAC control register (one per channel) DC-to-dc control register Software register Table 18. Programming the Main Control Register MSB D15 0 1 D14 0 D13 1 D12 POC D11 STATREAD D10 EWD D9 WD1 D8 WD0 D7 X1 D6 SHTCCTLIM D5 OUTEN_ALL D4 DCDC_ALL LSB D3 to D0 X1 X = don’t care. Table 19. Main Control Register Functions Bit POC STATREAD EWD WD1, WD0 SHTCCTLIM OUTEN_ALL DCDC_ALL Description The POC bit determines the state of the voltage output channels during normal operation. Its default value is 0. POC = 0. The output goes to the value set by the POC hardware pin when the voltage output is not enabled (default). POC = 1. The output goes to the opposite value of the POC hardware pin if the voltage output is not enabled. Enable status readback during a write. See the Device Features section. STATREAD = 1, enable. STATREAD = 0, disable (default). Enable watchdog timer. See the Device Features section for more information. EWD = 1, enable watchdog. EWD = 0, disable watchdog (default). Timeout select bits. Used to select the timeout period for the watchdog timer. WD1 WD0 Timeout Period (ms) 0 0 5 0 1 10 1 0 100 1 1 200 Programmable short-circuit limit on the VOUT_x pin in the event of a short-circuit condition. 0 = 16 mA (default). 1 = 8 mA. Enables the output on all four DACs simultaneously. Do not use the OUTEN_ALL bit when using the OUTEN bit in the DAC control register. When set, powers up the dc-to-dc converter on all four channels simultaneously. To power down the dc-to-dc converters, all channel outputs must first be disabled. Do not use the DCDC_ALL bit when using the DC_DC bit in the DAC control register. Rev. F | Page 35 of 51 AD5755-1 Data Sheet DAC Control Register The DAC control register is used to configure each DAC channel. The DAC control register options are shown in Table 20 and Table 21. Table 20. Programming DAC Control Register D15 0 1 D14 1 D13 0 D12 X1 D11 X1 D10 X1 D9 X1 D8 INT_ENABLE D7 CLR_EN D6 OUTEN D5 RSET D4 DC_DC D3 OVRNG D2 R2 D1 R1 D0 R0 X = don’t care. Table 21. DAC Control Register Functions Bit INT_ENABLE CLR_EN OUTEN RSET DC_DC OVRNG R2, R1, R0 Description Powers up the dc-to-dc converter, DAC, and internal amplifiers for the selected channel. Does not enable the output. Can only be done on a per channel basis. It is recommended to set this bit and allow a >200 µs delay before enabling the output because this results in a reduced output enable glitch. See Figure 31 and Figure 49 for plots of this glitch. Per channel clear enable bit. Selects if this channel clears when the CLEAR pin is activated. CLR_EN = 1, channel clears when the part is cleared. CLR_EN = 0, channel does not clear when the part is cleared (default). Enables/disables the selected output channel. OUTEN = 1, enables the channel. OUTEN = 0, disables the channel (default). Selects an internal or external current sense resistor for the selected DAC channel. RSET = 0, selects the external resistor (default). RSET = 1, selects the internal resistor. Powers the dc-to-dc converter on the selected channel. DC_DC = 1, power up the dc-to-dc converter. DC_DC = 0, power down the dc-to-dc converter (default). This allows per channel dc-to-dc converter power-up/power-down. To power down the dc-to-dc converter, the OUTEN and INT_ENABLE bits must also be set to 0. All dc-to-dc converters can also be powered up simultaneously using the DCDC_ALL bit in the main control register. Enables 20% overrange on voltage output channel only. No current output overrange available. OVRNG = 1, enabled. OVRNG = 0, disabled (default). Selects the output range to be enabled. R2 R1 R0 Output Range Selected 0 0 0 0 V to 5 V voltage range (default). 0 0 1 0 V to 10 V voltage range. 0 1 0 ±5 V voltage range. 0 1 1 ±10 V voltage range. 1 0 0 4 mA to 20 mA current range. 1 0 1 0 mA to 20 mA current range. 1 1 0 0 mA to 24 mA current range. Rev. F | Page 36 of 51 Data Sheet AD5755-1 Software Register The software register has three functions. It allows the user to perform a software reset to the device and enable the packet error checking feature (see the Packet Error Checking section) It is also used as part of the watchdog feature when it is enabled. This feature is useful to ensure that communication is not lost between the MCU and the AD5755-1 and that the datapath lines are working properly (that is, SDIN, SCLK, and SYNC). When the watchdog feature is enabled, the user must write 0x195 to the software register within the timeout period. If this command is not received within the timeout period, the ALERT pin signals a fault condition. This is only required when the watchdog timer function is enabled. DC-to-DC Control Register The dc-to-dc control register allows the user control over the dc-to-dc switching frequency and phase, as well as the maximum allowable dc-to-dc output voltage. The dc-to-dc control register options are shown in Table 24 and Table 25. Table 22. Programming the Software Register MSB D15 1 D14 0 D13 0 LSB D11 to D0 Reset code/SPI code D12 PEC enable Table 23. Software Register Functions Bit PEC Enable Description This bit selects if the packet error checking feature is enabled (see the Packet Error Checking section). 0 = PEC disabled. 1 = PEC enabled. Option Description Reset code Writing 0x555 to D[11:0] performs a reset of the AD5755-1. SPI code If the watchdog timer feature is enabled, 0x195 must be written to the software register (D11 to D0) within the programmed timeout period. Reset Code/SPI Code Table 24. Programming the DC-to-DC Control Register MSB D15 0 1 D14 1 D13 1 D12 to D7 X1 D6 DC-DC Comp D5 to D4 DC-DC phase D3 to D2 DC-DC Freq LSB D1 to D0 DC-DC MaxV X = don’t care. Table 25. DC-to-DC Control Register Options Bit DC-DC Comp DC-DC Phase DC-DC Freq DC-DC MaxV Description Selects between an internal and external compensation resistor for the dc-to-dc converter. See the DC-to-DC Converter Compensation Capacitors and AICC Supply Requirements—Slewing sections in the Device Features section for more information. 0 = selects the internal 150 kΩ compensation resistor (default). 1 = bypasses the internal compensation resistor for the dc-to-dc converter. In this mode, an external dc-to-dc compensation resistor must be used; this is placed at the COMPDCDC_x pin in series with the 10 nF dc-to-dc compensation capacitor to ground. Typically, a ~50 kΩ resistor is recommended. User programmable dc-to-dc converter phase (between channels). 00 = all dc-to-dc converters clock on the same edge (default). 01 = Channel A and Channel B clock on the same edge, Channel C and Channel D clock on opposite edges. 10 = Channel A and Channel C clock on the same edge, Channel B and Channel D clock on opposite edges. 11 = Channel A, Channel B, Channel C, and Channel D clock 90° out of phase from each other. DC-to-dc switching frequency; these are divided down from the internal 13 MHz oscillator (see Figure 70 and Figure 71). 00 = 250 ± 10% kHz. 01 = 410 ± 10% kHz (default). 10 = 650 ± 10% kHz. Maximum allowed VBOOST_x voltage supplied by the dc-to-dc converter. 00 = 23 V + 1 V/−1.5 V (default). 01 = 24.5 V ± 1 V. 10 = 27 V ± 1 V. 11 = 29.5 V ± 1 V. Rev. F | Page 37 of 51 AD5755-1 Data Sheet If the first clock edge in the NOP command is positive, the data readback is 24 bits of bits in length, consisting of eight don’t care bits prior to the 16 data bits (see Table 28). Slew Rate Control Register This register is used to program the slew rate control for the selected DAC channel. This feature is available on both the current and voltage outputs. The slew rate control is enabled/ disabled and programmed on a per channel basis. See Table 26 and the Digital Slew Rate Control section for more information. If the first clock edge in the NOP command is negative, the data readback is 23 bits in length, consisting of seven don’t care bits prior to the 16 data bits (see Table 29). In both cases, if PEC is enabled, there must be no activity on SCLK between the read command and NOP command, or an incorrect PEC may be read back (see Figure 6). READBACK OPERATION Readback mode is invoked by setting the R/W bit = 1 in the serial input register write. See Table 27 for the bits associated with a readback operation. The DUT_AD1 and DUT_AD0 bits, in association with Bits RD[4:0], select the register to be read. The remaining data bits in the write sequence are don’t cares. During the next SPI transfer (see Figure 4), the data appearing on the SDO output contains the data from the previously addressed register. This second SPI transfer must either be a request to read yet another register on a third data transfer or a no operation command. The no operation command for DUT Address 00 is 0x1CE000, for other DUT addresses, Bits D22 and D21 are set accordingly. Readback Example To read back the gain register of Device 1, Channel A on the AD5755-1, implement the following sequence: 1. Write 0xA80000 to the AD5755-1 input register. This configures the AD5755-1 Device Address 1 for read mode with the gain register of Channel A selected. All the data bits, D15 to D0, are don’t cares. Follow with another read command or a no operation command (0x3CE000). During this command, the data from the Channel A gain register is clocked out on the SDO line. 2. The data readback is set in the 16 LSBs. The MSBs consist of don’t care bits. The number of don’t care bits is dependent of the polarity of the first clock edge within the SYNC phase of the NOP command (see Figure 4). Table 26. Programming the Slew Rate Control Register D15 0 1 D14 0 D13 0 D12 SREN D11 to D7 X1 D6 to D3 SR_CLOCK D2 to D0 SR_STEP X = don’t care. Table 27. Input Shift Register Contents for a Read Operation D23 R/W 1 D22 DUT_AD1 D21 DUT_AD0 D20 RD4 D19 RD3 D18 RD2 D17 RD1 D16 RD0 D15 to D0 X1 X = don’t care. Table 28. Decoding Data Readback on SDO (First Clock Edge Within the SYNC Frame of NOP Command is Positive) D23 X1 1 D22 X1 D21 X1 D20 X1 D19 X1 D18 X1 D17 X1 D16 X1 D15 to D0 Data Readback X = don’t care. Table 29. Decoding Data Readback on SDO (First Clock Edge Within the SYNC Frame of NOP Command is Negative) D22 X1 1 D21 X1 D20 X1 D19 X1 D18 X1 D17 X1 X = don’t care. Rev. F | Page 38 of 51 D16 X1 D15 to D0 Data Readback Data Sheet AD5755-1 Table 30. Read Address Decoding RD4 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 1 1 1 1 1 1 1 1 1 1 RD3 0 0 0 0 0 0 0 0 1 1 1 1 1 1 1 1 0 0 0 0 0 0 0 0 1 1 1 RD2 0 0 0 0 1 1 1 1 0 0 0 0 1 1 1 1 0 0 0 0 1 1 1 1 0 0 0 RD1 0 0 1 1 0 0 1 1 0 0 1 1 0 0 1 1 0 0 1 1 0 0 1 1 0 0 1 RD0 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 Function Read DAC A data register Read DAC B data register Read DAC C data register Read DAC D data register Read DAC A control register Read DAC B control register Read DAC C control register Read DAC D control register Read DAC A gain register Read DAC B gain register Read DAC C gain register Read DAC D gain register Read DACA offset register Read DAC B offset register Read DAC C offset register Read DAC D offset register Clear DAC A code register Clear DAC B code register Clear DAC C code register Clear DAC D code register DAC A slew rate control register DAC B slew rate control register DAC C slew rate control register DAC D slew rate control register Read status register Read main control register Read dc-to-dc control register Rev. F | Page 39 of 51 AD5755-1 Data Sheet Status Register read back on the SDO pin during every write sequence. Alternatively, if the STATREAD bit is not set, the status register can be read using the normal readback operation. The status register is a read only register. This register contains any fault information, the status of the packet error checking feature, and a ramp active bit. When the STATREAD bit in the main control register is set, the status register contents can be Table 31. Decoding the Status Register MSB D15 DCDCD D14 DCDCC D13 DCDCB D12 DCDCA D11 PEC enabled D10 PEC error D9 Ramp active D8 Over TEMP D7 VOUT_D fault D6 VOUT_C fault D5 VOUT_B fault D4 VOUT_A fault D3 IOUT_D fault D2 IOUT_C fault D1 IOUT_B fault LSB D0 IOUT_A fault Table 32. Status Register Options Bit DC-DCD DC-DCC DC-DCB DC-DCA PEC Enabled PEC Error Ramp Active Over TEMP VOUT_D Fault VOUT_C Fault VOUT_B Fault VOUT_A Fault IOUT_D Fault IOUT_C Fault IOUT_B Fault IOUT_A Fault Description In current output mode, this bit is set on Channel D if the dc-to-dc converter cannot maintain compliance (it may be reaching its VMAX voltage). In this case, the IOUT_D fault bit is also set. See the DC-to-DC Converter VMAX Functionality section for more information on the operation of this bit under this condition. In voltage output mode, this bit is set if, on Channel D, the dc-to-dc converter is unable to regulate to 15 V as expected. When this bit is set, it does not result in the FAULT pin going high. In current output mode, this bit is set on Channel C if the dc-to-dc converter cannot maintain compliance (it may be reaching its VMAX voltage). In this case, the IOUT_C fault bit is also set. See the DC-to-DC Converter VMAX Functionality section for more information on the operation of this bit under this condition. In voltage output mode, this bit is set if, on Channel C, the dc-to-dc converter is unable to regulate to 15 V as expected. When this bit is set, it does not result in the FAULT pin going high. In current output mode, this bit is set on Channel B if the dc-to-dc converter cannot maintain compliance (it may be reaching its VMAX voltage). In this case, the IOUT_B fault bit is also set. See the DC-to-DC Converter VMAX Functionality section for more information on the operation of this bit under this condition. In voltage output mode, this bit is set if, on Channel B, the dc-to-dc converter is unable to regulate to 15 V as expected. When this bit is set, it does not result in the FAULT pin going high. In current output mode, this bit is set on Channel A if the dc-to-dc converter cannot maintain compliance (it may be reaching its VMAX voltage). In this case, the IOUT_A fault bit is also set. See the DC-to-DC Converter VMAX Functionality section for more information on the operation of this bit under this condition. In voltage output mode, this bit is set if, on Channel A, the dc-to-dc converter is unable to regulate to 15 V as expected. When this bit is set, it does not result in the FAULT pin going high. This is a read only bit. It allows the user to verify the status of the packet error checking feature. Denotes a PEC error on the last data-word received over the SPI interface. This bit is set while any one of the output channels is slewing (slew rate control is enabled on at least one channel). This bit is set if the AD5755-1 core temperature exceeds approximately 150°C. This bit is set if a fault is detected on the VOUT_D pin. This bit is set if a fault is detected on the VOUT_C pin. This bit is set if a fault is detected on the VOUT_B pin. This bit is set if a fault is detected on the VOUT_A pin. This bit is set if a fault is detected on the IOUT_D pin. This bit is set if a fault is detected on the IOUT_C pin. This bit is set if a fault is detected on the IOUT_B pin. This bit is set if a fault is detected on the IOUT_A pin. Rev. F | Page 40 of 51 Data Sheet AD5755-1 DEVICE FEATURES OUTPUT FAULT The AD5755-1 is equipped with a FAULT pin, an active low open-drain output allowing several AD5755-1 devices to be connected together to one pull-up resistor for global fault detection. The FAULT pin is forced active by any one of the following fault scenarios: DAC INPUT REGISTER DAC DATA REGISTER DAC 09226-075 M REGISTER C REGISTER Figure 78. Digital Offset and Gain Control The voltage at IOUT_x attempts to rise above the compliance range due to an open-loop circuit or insufficient power supply voltage. The internal circuitry that develops the fault output avoids using a comparator with windowed limits because this requires an actual output error before the FAULT output becomes active. Instead, the signal is generated when the internal amplifier in the output stage has less than approximately 1 V of remaining drive capability. Thus, the FAULT output activates slightly before the compliance limit is reached. A short is detected on a voltage output pin. The shortcircuit current is limited to 16 mA or 8 mA, which is programmable by the user. If using the AD5755-1 in unipolar supply mode, a short-circuit fault may be generated if the output voltage is below 50 mV. An interface error is detected due to a PEC failure. See the Packet Error Checking section. If the core temperature of the AD5755-1 exceeds approximately 150°C. The VOUT_x fault, IOUT_x fault, PEC error, and over TEMP bits of the status register are used in conjunction with the FAULT output to inform the user which one of the fault conditions caused the FAULT output to be activated. VOLTAGE OUTPUT SHORT-CIRCUIT PROTECTION Under normal operation, the voltage output sinks/sources up to 12 mA and maintains specified operation. The maximum output current or short-circuit current is programmable by the user and can be set to 16 mA or 8 mA. If a short circuit is detected, the FAULT goes low and the relevant VOUT_x fault bit in the status register is set. DIGITAL OFFSET AND GAIN CONTROL Each DAC channel has a gain (M) and offset (C) register, which allow trimming out of the gain and offset errors of the entire signal chain. Data from the DAC data register is operated on by a digital multiplier and adder controlled by the contents of the M and C registers. The calibrated DAC data is then stored in the DAC input register. Although Figure 78 indicates a multiplier and adder for each channel, there is only one multiplier and one adder in the device, and they are shared among all four channels. This has implications for the update speed when several channels are updated at once (see Table 3). Each time data is written to the M or C register, the output is not automatically updated. Instead, the next write to the DAC channel uses these M and C values to perform a new calibration and automatically updates the channel. The output data from the calibration is routed to the DAC input register. This is then loaded to the DAC as described in the Theory of Operation section. Both the gain register and the offset register have 16 bits of resolution. The correct method to calibrate the gain/offset is to first calibrate out the gain and then calibrate the offset. The value (in decimal) that is written to the DAC input register can be calculated by Code DACRegister D ( M 1) 216 C 215 (1) where: D is the code loaded to the DAC channel’s input register. M is the code in the gain register (default code = 216 – 1). C is the code in the offset register (default code = 215). STATUS READBACK DURING A WRITE The AD5755-1 has the ability to read back the status register contents during every write sequence. This feature is enabled via the STATREAD bit in the main control register. This allows the user to continuously monitor the status register and act quickly in the case of a fault. When status readback during a write is enabled, the contents of the 16-bit status register (see Table 32) are output on the SDO pin, as shown in Figure 6. The AD5755-1 powers up with this feature disabled. When this is enabled, the normal readback feature is not available, except for the status register. To read back any other register, clear the STATREAD bit first before following the readback sequence. STATREAD can be set high again after the register read. If there are multiple units on the same SDO bus which have the STATREAD feature enabled, ensure that each unit is provided a unique physical address (AD1 and AD0) to prevent contention on the bus. If packet error checking is enabled, ignore the PEC values returned on a status readback during a write operation. See the Packet Error Checking section for more information. Rev. F | Page 41 of 51 AD5755-1 Data Sheet The PEC can be used for both transmit and receive of data packets. If status readback during a write is enabled, ignore the PEC values returned during the status readback during a write operation. If status readback during a write is disabled, the user can still use the normal readback operation to monitor status register activity with PEC. ASYNCHRONOUS CLEAR CLEAR is an active high, edge-sensitive input that allows the output to be cleared to a preprogrammed 16-bit code. This code is user programmable via a per channel 16-bit clear code register. For a channel to clear, that channel must be enabled to be cleared via the CLR_EN bit in the channel’s DAC control register. If the channel is not enabled to be cleared, then the output remains in its current state independent of the CLEAR pin level. If PEC is enabled when receiving data packets, there must be no activity on SCLK between the read command and NOP command, or an incorrect PEC may be read back. See Figure 5 and the Readback Operation for further information. When the CLEAR signal is returned low, the relevant outputs remain cleared until a new value is programmed. WATCHDOG TIMER When enabled, an on-chip watchdog timer generates an alert signal if 0x195 has not been written to the software register within the programmed timeout period. This feature is useful to ensure that communication is not lost between the MCU and the AD5755-1 and that these datapath lines are working properly (that is, SDIN, SCLK, and SYNC). If 0x195 is not received by the software register within the timeout period, the ALERT pin signals a fault condition. The ALERT signal is active high and can be connected directly to the CLEAR pin to enable a clear in the event that communication from the MCU is lost. PACKET ERROR CHECKING To verify that data has been received correctly in noisy environments, the AD5755-1 offers the option of packet error checking based on an 8-bit cyclic redundancy check (CRC-8). The device controlling the AD5755-1 generates an 8-bit frame check sequence using the polynomial C(x) = x8 + x2 + x1 + 1 This is added to the end of the data-word, and 32 bits are sent to the AD5755-1 before taking SYNC high. If the packet error checking enable bit is set high (Bit 12 in the software register), the user must supply a 32-bit frame that contains the 24 data bits and 8-bit CRC. If the check is valid, the data is written to the selected register. If the error check fails, the FAULT pin goes low and the PEC error bit in the status register is set. After reading the status register, FAULT returns high (assuming there are no other faults), and the PEC error bit is cleared automatically. It is not recommended to tie both AD1 and AD0 low because a short low on SDIN, that is, a command of 16 zeroes, may possibly lead to a zero-scale update for DAC A. The watchdog timer is enabled, and the timeout period (5 ms, 10 ms, 100 ms, or 200 ms) is set in the main control register (see Table 18 and Table 19). OUTPUT ALERT The AD5755-1 is equipped with an ALERT pin. This is an active high CMOS output. The AD5755-1 also has an internal watchdog timer. When enabled, it monitors SPI communications. If 0x195 is not received by the software register within the timeout period, the ALERT pin goes active. INTERNAL REFERENCE UPDATE ON SYNC HIGH SYNC The AD5755-1 contains an integrated +5 V voltage reference with initial accuracy of ±5 mV maximum and a temperature drift coefficient of ±10 ppm maximum. The reference voltage is buffered and externally available for use elsewhere within the system. REFOUT must be connected to REFIN to use the internal reference. SCLK MSB D23 SDIN LSB D0 24-BIT DATA EXTERNAL CURRENT SETTING RESISTOR 24-BIT DATA TRANSFER—NO ERROR CHECKING Referring to Figure 74, RSET is an internal sense resistor as part of the voltage-to-current conversion circuitry. The stability of the output current value over temperature is dependent on the stability of the value of RSET. As a method of improving the stability of the output current over temperature, an external 15 kΩ low drift resistor can be connected to the RSET_x pin of the AD5755-1 to be used instead of the internal resistor, R1. The external resistor is selected via the DAC control register (see Table 20). UPDATE ON SYNC HIGH ONLY IF ERROR CHECK PASSED SYNC SCLK SDIN FAULT LSB D8 24-BIT DATA D7 D0 8-BIT CRC FAULT PIN GOES LOW IF ERROR CHECK FAILS 32-BIT DATA TRANSFER WITH ERROR CHECKING Figure 79. PEC Timing 09226-180 MSB D31 Table 1 outlines the performance specifications of the AD5755-1 with both the internal RSET resistor and an external, 15 kΩ RSET resistor. Using an external RSET resistor allows for improved performance over the internal RSET resistor option. The external RSET resistor specification assumes an ideal resistor; the actual Rev. F | Page 42 of 51 Data Sheet AD5755-1 performance depends on the absolute value and temperature coefficient of the resistor used. This directly affects the gain error of the output, and thus the total unadjusted error. To arrive at the gain/TUE error of the output with a particular external RSET resistor, add the percentage absolute error of the RSET resistor directly to the gain/TUE error of the AD5755-1 with the external RSET resistor, shown in Table 1 (expressed in % FSR). HART CONNECTIVITY The AD5755-1 has four CHART pins, one corresponding to each output channels. A HART signal can be coupled into these pins. The HART signal appears on the corresponding current output, if the output is enabled. Table 33 shows the recommended input voltages for the HART signal at the CHART pin. If these voltages are used, the current output must meet the HART amplitude specifications. Figure 80 shows the recommended circuit for attenuating and coupling in the HART signal. Table 33. CHART Input Voltage to HART Output Current RSET Internal RSET External RSET CHART Input Voltage 150 mV p-p 170 mV p-p Current Output (HART) 1 mA p-p 1 mA p-p CHARTx SR_CLOCK 0000 0001 0010 0011 0100 0101 0110 0111 1000 1001 1010 1011 1100 1101 1110 1111 Update Clock Frequency (Hz)1 64 k 32 k 16 k 8k 4k 2k 1k 500 250 125 64 32 16 8 4 0.5 These clock frequencies are divided down from the 13 MHz internal oscillator. See Table 1, Figure 70, and Figure 71. Table 35. Slew Rate Step Size Options 09226-076 C2 Table 34. Slew Rate Update Clock Options 1 C1 HART MODEM OUTPUT outline the range of values for both the SR_CLOCK and SR_STEP parameters. Digitally controlling the slew rate of the output is necessary to meet the analog rate of change requirements for HART. SR_STEP 000 001 010 011 100 101 110 111 If the HART feature is not required, leave the CHART pins open circuit. The following equation describes the slew rate as a function of the step size, the update clock frequency, and the LSB size: Figure 80. Coupling HART Signal A minimum capacitance of C1 + C2 is required to ensure that the 1.2 kHz and 2.2 kHz HART frequencies are not significantly attenuated at the output. The recommended values are C1 = 22 nF, C2 = 47 nF. DIGITAL SLEW RATE CONTROL Step Size (LSBs) 1 2 4 16 32 64 128 256 Slew Time = The slew rate control feature of the AD5755-1 allows the user to control the rate at which the output value changes. This feature is available on both the current and voltage outputs. With the slew rate control feature disabled, the output value changes at a rate limited by the output drive circuitry and the attached load. To reduce the slew rate, this can be achieved by enabling the slew rate control feature. With the feature enabled via the SREN bit of the slew rate control register (see Table 26), the output, instead of slewing directly between two values, steps digitally at a rate defined by two parameters accessible via the slew rate control register, as shown in Table 26. The parameters are SR_CLOCK and SR_STEP. SR_CLOCK defines the rate at which the digital slew is updated, for example, if the selected update rate is 8 kHz, the output updates every 125 µs. In conjunction with this, SR_STEP defines by how much the output value changes at each update. Together, both parameters define the rate of change of the output value. Table 34 and Table 35 Output Change Step Size × Update Clock Frequency × LSB Size where: Slew Time is expressed in seconds. Output Change is expressed in amps for IOUT_x or volts for VOUT_x. When the slew rate control feature is enabled, all output changes occur at the programmed slew rate (see the DC-to-DC Converter Settling Time section for additional information). For example, if the CLEAR pin is asserted, the output slews to the clear value at the programmed slew rate (assuming that the clear channel is enabled to be cleared). If a number of channels are enabled for slew, care must be taken when asserting the CLEAR pin. If one of the channels is slewing when CLEAR is asserted, other channels may change directly to their clear values not under slew rate control. The update clock frequency for any given value is the same for all output ranges. The step size, however, varies Rev. F | Page 43 of 51 AD5755-1 Data Sheet across output ranges for a given value of step size because the LSB size is different for each output range. POWER DISSIPATION CONTROL The AD5755-1 contains integrated dynamic power control using a dc-to-dc boost converter circuit, allowing reductions in power consumption from standard designs when using the part in current output mode. In standard current input module designs, the load resistor values can range from typically 50 Ω to 750 Ω. Output module systems must source enough voltage to meet the compliance voltage requirement across the full range of load resistor values. For example, in a 4 mA to 20 mA loop when driving 20 mA, a compliance voltage of >15 V is required. When driving 20 mA into a 50 Ω load, only 1 V compliance is required. The AD5755-1 circuitry senses the output voltage and regulates this voltage to meet compliance requirements plus a small headroom voltage. The AD5755-1 is capable of driving up to 24 mA through a 1 kΩ load. DC-TO-DC CONVERTERS The AD5755-1 contains four independent dc-to-dc converters. These are used to provide dynamic control of the VBOOST supply voltage for each channel (see Figure 74). Figure 81 shows the discrete components needed for the dc-to-dc circuitry, and the following sections describe component selection and operation of this circuitry. 10µH CDCDC 4.7µF RFILTER 10Ω VBOOST_X CFILTER 0.1µF SWx When a channel current output is enabled, the converter regulates the VBOOST_x supply to 7.4 V (±5%) or (IOUT × RLOAD + Headroom), whichever is greater (see Figure 54 for a plot of headroom supplied vs. output current). In voltage output mode with the output disabled, the converter regulates the VBOOST_x supply to +15 V (±5%). In current output mode with the output disabled, the converter regulates the VBOOST_x supply to 7.4 V (±5%). Within a channel, the VOUT_x and IOUT_x stages share a common VBOOST_x supply so that the outputs of the IOUT_x and VOUT_x stages can be tied together. DC-to-DC Converter Settling Time When in current output mode, the settling time for a step greater than ~1 V (IOUT × RLOAD) is dominated by the settling time of the dc-to-dc converter. The exception to this is when the required voltage at the IOUT_x pin plus the compliance voltage is below 7.4 V (±5%). A typical plot of the output settling time can be found in Figure 50. This plot is for a 1 kΩ load. The settling time for smaller loads is faster. The settling time for current steps less than 24 mA is also faster. DC-to-DC Converter VMAX Functionality The maximum VBOOST_x voltage is set in the dc-to-dc control register (23 V, 24.5 V, 27 V, or 29.5 V; see Table 25). On reaching this maximum voltage, the dc-to-dc converter is disabled, and the VBOOST_x voltage is allowed to decay by ~0.4 V. After the VBOOST_x voltage has decayed by ~0.4 V, the dc-to-dc converter is reenabled, and the voltage ramps up again to VMAX, if still required. This operation is shown in Figure 82. 29.6 Figure 81. DC-to-DC Circuit Table 36. Recommended DC-to-DC Components Component XAL4040-103 GRM32ER71H475KA88L PD3S160-7 Value 10 µH 4.7 µF 0.55 VF 0mA TO 24mA RANGE, 24mA OUTPUT OUTPUT UNLOADED 29.4 Manufacturer Coilcraft® Murata Diodes, Inc. It is recommended to place a 10 Ω, 100 nF low-pass RC filter after CDCDC. This consumes a small amount of power but reduces the amount of ripple on the VBOOST_x supply. VBOOST VOLTAGE (V) Symbol LDCDC CDCDC DDCDC VMAX DC_DC BIT 29.5 29.3 29.2 29.1 DC-DCMaxV = 11 (29.5V) DCDCx BIT = 1 29.0 fSW = 410kHz 28.9 TA = 25°C 28.8 28.7 DCDCx BIT = 0 DC-to-DC Converter Operation 28.6 The on-board dc-to-dc converters use a constant frequency, peak current mode control scheme to step up an AVCC input of 4.5 V to 5.5 V to drive the AD5755-1 output channel. These are designed to operate in discontinuous conduction mode (DCM) with a duty cycle of <90% typical. Discontinuous conduction mode refers to a mode of operation where the inductor current goes to zero for an appreciable percentage of the switching cycle. The dc-to-dc converters are nonsynchronous; that is, they require an external Schottky diode. 0 0.5 1.0 1.5 2.0 2.5 TIME (ms) 3.0 3.5 4.0 09226-183 CIN ≥10µF DDCDC 09226-077 LDCDC AVCC DC-to-DC Converter Output Voltage Figure 82. Operation on Reaching VMAX As can be seen in Figure 82, the DC-DCx bit in the status register asserts when the AD5755-1 is ramping to the VMAX value but deasserts when the voltage is decaying to VMAX − ~0.4 V. DC-to-DC Converter On-Board Switch The AD5755-1 contains a 0.425 Ω internal switch. The switch current is monitored on a pulse by pulse basis and is limited to 0.8 A peak current. Rev. F | Page 44 of 51 Data Sheet AD5755-1 DC-to-DC Converter Switching Frequency and Phase The AD5755-1 dc-to-dc converter switching frequency can be selected from the dc-to-dc control register. The phasing of the channels can also be adjusted so that the dc-to-dc converter can clock on different edges (see Table 25). For typical applications, a 410 kHz frequency is recommended. At light loads (low output current and small load resistor), the dc-to-dc converter enters a pulse-skipping mode to minimize switching power dissipation. DC-to-DC Converter Inductor Selection For typical 4 mA to 20 mA applications, a 10 µH inductor (such as the XAL4040-103 from Coilcraft), combined with a switching frequency of 410 kHz, allows up to 24 mA to be driven into a load resistance of up to 1 kΩ with an AVCC supply of 4.5 V to 5.5 V. It is important to ensure that the inductor is able to handle the peak current without saturating, especially at the maximum ambient temperature. If the inductor enters into saturation mode, it results in a decrease in efficiency. The inductance value also drops during saturation and may result in the dc-to-dc converter circuit not being able to supply the required output power. DC-to-DC Converter External Schottky Selection The AD5755-1 requires an external Schottky for correct operation. Ensure that the Schottky is rated to handle the maximum reverse breakdown expected in operation and that the rectifier maximum junction temperature is not exceeded. The diode average current is approximately equal to the ILOAD current. Diodes with larger forward voltage drops result in a decrease in efficiency. DC-to-DC Converter Compensation Capacitors As the dc-to-dc converter operates in DCM, the uncompensated transfer function is essentially a single-pole transfer function. The pole frequency of the transfer function is determined by the output capacitance of the dc-to-dc converter, input and output voltage, and output load. The AD5755-1 uses an external capacitor in conjunction with an internal 150 kΩ resistor to compensate the regulator loop. Alternatively, an external compensation resistor can be used in series with the compensation capacitor, by setting the DC-DC Comp bit in the dc-to-dc control register. In this case, a ~50 kΩ resistor is recommended. A description of the advantages of this can be found in the AICC Supply Requirements—Slewing section. For typical applications, a 10 nF dc-to-dc compensation capacitor is recommended. DC-to-DC Converter Input and Output Capacitor Selection The output capacitor affects ripple voltage of the dc-to-dc converter and indirectly limits the maximum slew rate at which the channel output current can rise. The ripple voltage is caused by a combination of the capacitance and equivalent series resistance (ESR) of the capacitor. For the AD5755-1, a ceramic capacitor of 4.7 µF is recommended for typical applications. Larger capacitors or paralleled capacitors improve the ripple at the expense of reduced slew rate. Larger capacitors also impact the AVCC supplies current requirements while slewing (see the AICC Supply Requirements—Slewing section). This capacitance at the output of the dc-to-dc converter must be >3 µF under all operating conditions. The input capacitor provides much of the dynamic current required for the dc-to-dc converter and must be a low ESR component. For the AD5755-1, a low ESR tantalum or ceramic capacitor of 10 µF is recommended for typical applications. Ceramic capacitors must be chosen carefully because they can exhibit a large sensitivity to dc bias voltages and temperature. X5R or X7R dielectrics are preferred because these capacitors remain stable over wider operating voltage and temperature ranges. Care must be taken if selecting a tantalum capacitor to ensure a low ESR value. AICC SUPPLY REQUIREMENTS—STATIC The dc-to-dc converter is designed to supply a VBOOST_x voltage of VBOOST = IOUT × RLOAD + Headroom (2) See Figure 54 for a plot of headroom supplied vs. output voltage. This means that, for a fixed load and output voltage, the dc-to-dc converter output current can be calculated by the following formula: AI CC = Power Out Efficiency × AVCC = I OUT × VBOOST η VBOOST × AVCC (3) where: IOUT is the output current from IOUT_x in amps. ηVBOOST is the efficiency at VBOOST_x as a fraction (see Figure 56 and Figure 57). AICC SUPPLY REQUIREMENTS—SLEWING The AICC current requirement while slewing is greater than in static operation because the output power increases to charge the output capacitance of the dc-to-dc converter. This transient current can be quite large (see Figure 83), although the methods described in the Reducing AICC Current Requirements section can reduce the requirements on the AVCC supply. If not enough AICC current can be provided, the AVCC voltage drops. Due to this AVCC drop, the AICC current required to slew increases further. This means that the voltage at AVCC drops further (see Equation 3) and the VBOOST_x voltage, and thus the output voltage, may never reach its intended value. Because this AVCC voltage is common to all channels, this may also affect other channels. Rev. F | Page 45 of 51 AD5755-1 Data Sheet 0.8 0.4 20 15 0.3 10 0.2 AICC IOUT VBOOST 0.1 5 0 0 0 0.5 1.0 1.5 TIME (ms) 2.0 0.6 2.5 A compensation resistor can be placed at the COMPDCDC_x pin in series with the 10 nF compensation capacitor. A 51 kΩ external compensation resistor is recommended. This compensation increases the slew time of the current output but eases the AICC transient current requirements. Figure 84 shows a plot of AICC current for a 24 mA step through a 1 kΩ load when using a 51 kΩ compensation resistor. This method eases the current requirements through smaller loads even further, as shown in Figure 85. 0.5 20 0.4 16 0.3 12 0.2 8 AICC IOUT VBOOST 0.1 4 IOUT_x CURRENT (mA)/VBOOST_x VOLTAGE (V) 24 0 0 0 0.5 1.0 1.5 TIME (ms) 2.0 2.5 0.4 16 0.3 12 0.2 8 0.1 4 0 0.5 1.0 1.5 TIME (ms) 2.0 2.5 Using slew rate control can greatly reduce the AVCC supplies current requirements, as shown in Figure 86. When using slew rate control, pay attention to the fact that the output cannot slew faster than the dc-to-dc converter. The dc-to-dc converter slews slowest at higher currents through large (for example, 1 kΩ) loads. This slew rate is also dependent on the configuration of the dc-to-dc converter. Two examples of the dc-to-dc converter output slew are shown in Figure 84 and Figure 85 (VBOOST corresponds to the dc-to-dc converter’s output voltage). 0.8 32 0mA TO 24mA RANGE 1kΩ LOAD fSW = 410kHz INDUCTOR = 10µH (XAL4040-103) TA = 25°C 0.7 0.6 28 24 AICC IOUT VBOOST 0.5 20 0.4 16 0.3 12 0.2 8 0.1 4 0 0 0 1 2 3 TIME (ms) 4 5 6 Figure 86. AICC Current vs. Time for 24 mA Step Through 1 kΩ Load with Slew Rate Control 09226-185 0.6 AICC CURRENT (A) 32 28 20 0 AICC CURRENT (A) There are two main methods that can be used to reduce the AICC current requirements. One method is to add an external compensation resistor, and the other is to use slew rate control. Both of these methods can be used in conjunction. 0.7 0.5 Figure 85. AICC Current vs. Time for 24 mA Step Through 500 Ω Load with External 51 kΩ Compensation Resistor Reducing AICC Current Requirements 0mA TO 24mA RANGE 1kΩ LOAD fSW = 410kHz INDUCTOR = 10µH (XAL4040-103) TA = 25°C 24 0 Figure 83. AICC Current vs. Time for 24 mA Step Through 1 kΩ Load with Internal Compensation Resistor 0.8 28 IOUT_x CURRENT (mA)/VBOOST_x VOLTAGE (V) 0.5 0mA TO 24mA RANGE 500Ω LOAD fSW = 410kHz INDUCTOR = 10µH (XAL4040-103) TA = 25°C 09226-186 0mA TO 24mA RANGE 1kΩ LOAD fSW = 410kHz INDUCTOR = 10µH (XAL4040-103) TA = 25°C 09226-184 AICC CURRENT (A) 0.6 0.7 IOUT_x CURRENT (mA)/VBOOST_x VOLTAGE (V) 25 32 AICC IOUT VBOOST Figure 84. AICC Current vs. Time for 24 mA Step Through 1 kΩ Load with External 51 kΩ Compensation Resistor Rev. F | Page 46 of 51 09226-187 0.7 AICC CURRENT (A) 30 IOUT_x CURRENT (mA)/VBOOST_x VOLTAGE (V) 0.8 Data Sheet AD5755-1 APPLICATIONS INFORMATION VOLTAGE AND CURRENT OUTPUT RANGES ON THE SAME TERMINAL When using a channel of the AD5755-1, the current and voltage output pins can be connected to two separate terminals or tied together and connected to a single terminal. There is no conflict with tying the two output pins together because only the voltage output or the current output can be enabled at any one time. When the current output is enabled, the voltage output is in tristate mode, and when the voltage output is enabled, the current output is in tristate mode. For this operation, the POC pin must be tied low and the POC bit in the main control register set to 0, or, if the POC pin is tied high, the POC bit in the main control register must be set to 1 before the current output is enabled. As shown in the Absolute Maximum Ratings section, the output tolerances are the same for both the voltage and current output pins. The +VSENSE_x connections are buffered so that current leakage into these pins is negligible when in current output mode. CURRENT OUTPUT MODE WITH INTERNAL RSET When using the internal RSET resistor in current output mode, the output is significantly affected by how many other channels using the internal RSET are enabled and by the dc crosstalk from these channels. The internal RSET specifications in Table 1 are for all channels enabled with the internal RSET selected and outputting the same code. For every channel enabled with the internal RSET, the offset error decreases. For example, with one current output enabled using the internal RSET, the offset error is 0.075% FSR. This value decreases proportionally as more current channels are enabled; the offset error is 0.056% FSR on each of two channels, 0.029% on each of three channels, and 0.01% on each of four channels. Similarly, the dc crosstalk when using the internal RSET is proportional to the number of current output channels enabled with the internal RSET. For example, with the measured channel at 0x8000 and one channel going from zero to full scale, the dc crosstalk is −0.011% FSR. With two channels going from zero to full scale, it is −0.019% FSR, and with all three other channels going from zero to full scale, it is −0.025% FSR. For the full-scale error measurement in Table 1, all channels are at 0xFFFF. This means that, as any channel goes to zero scale, the full-scale error increases due to the dc crosstalk. For example, with the measured channel at 0xFFFF and three channels at zero scale, the full-scale error is 0.025%. Similarly, if only one channel is enabled in current output mode with the internal RSET, the full-scale error is 0.025% FSR + 0.075% FSR = 0.1% FSR. PRECISION VOLTAGE REFERENCE SELECTION To achieve the optimum performance from the AD5755-1 over its full operating temperature range, a precision voltage reference must be used. Give thought to the selection of a precision voltage reference. The voltage applied to the reference inputs is used to provide a buffered reference for the DAC cores. Therefore, any error in the voltage reference is reflected in the outputs of the device. There are four possible sources of error to consider when choosing a voltage reference for high accuracy applications: initial accuracy, temperature coefficient of the output voltage, long term drift, and output voltage noise. Initial accuracy error on the output voltage of an external reference can lead to a full-scale error in the DAC. Therefore, to minimize these errors, a reference with low initial accuracy error specification is preferred. Choosing a reference with an output trim adjustment, such as the ADR425, allows a system designer to trim system errors out by setting the reference voltage to a voltage other than the nominal. The trim adjustment can be used at any temperature to trim out any error. Long-term drift is a measure of how much the reference output voltage drifts over time. A reference with a tight long-term drift specification ensures that the overall solution remains relatively stable over its entire lifetime. The temperature coefficient of a reference’s output voltage affects INL, DNL, and TUE. Choose a reference with a tight temperature coefficient specification to reduce the dependence of the DAC output voltage to ambient temperature. In high accuracy applications, which have a relatively low noise budget, reference output voltage noise must be considered. Choosing a reference with as low an output noise voltage as practical for the system resolution required is important. Precision voltage references such as the ADR435 (XFET design) produce low output noise in the 0.1 Hz to 10 Hz region. However, as the circuit bandwidth increases, filtering the output of the reference may be required to minimize the output noise. Table 37. Recommended Precision References Part No. ADR445 ADR02 ADR435 ADR395 AD586 Initial Accuracy (mV Maximum) ±2 ±3 ±2 ±5 ±2.5 Long-Term Drift (ppm Typical) 50 50 40 50 15 Temperature Drift (ppm/°C Maximum) 3 3 3 9 10 Rev. F | Page 47 of 51 0.1 Hz to 10 Hz Noise (µV p-p Typical) 2.25 10 8 8 4 AD5755-1 Data Sheet DRIVING INDUCTIVE LOADS MICROPROCESSOR INTERFACING When driving inductive or poorly defined loads, a capacitor may be required between IOUT_x and AGND to ensure stability. A 0.01 μF capacitor between IOUT_x and AGND ensures stability of a load of 50 mH. The capacitive component of the load may cause slower settling, although this may be masked by the settling time of the AD5755-1. There is no maximum capacitance limit for the current output of the AD5755-1. Microprocessor interfacing to the AD5755-1 is via a serial bus that uses a protocol compatible with microcontrollers and DSP processors. The communications channel is a 3-wire minimum interface consisting of a clock signal, a data signal, and a latch signal. The AD5755-1 requires a 24-bit data-word with data valid on the falling edge of SCLK. TRANSIENT VOLTAGE PROTECTION The AD5755-1 contains ESD protection diodes that prevent damage from normal handling. The industrial control environment can, however, subject I/O circuits to much higher transients. To protect the AD5755-1 from excessively high voltage transients, external power diodes and a surge current limiting resistor (RP) are required, as shown in Figure 87. A typical value for RP is 10 Ω. The two protection diodes and the resistor (RP) must have appropriate power ratings. The AD5755-1 can be connected directly to the SPORT interface of the ADSP-BF527, an Analog Devices, Inc., Blackfin® DSP. Figure 88 shows how the SPORT interface can be connected to control the AD5755-1. AD5755-1 10Ω SPORT_TFS SYNC SPORT_TSCK SCLK SPORT_DTO CFILTER 0.1µF VBOOST_x AD5755-1 AGND ADSP-BF527 D2 GPIO0 RP IOUT_x D1 AVSS SDIN RLOAD LDAC 09226-080 CDCDC 4.7µF AD5755-1-to-ADSP-BF527 Interface RFILTER 09226-079 (FROM DC-TO-DC CONVERTER) The DAC output update is initiated on either the rising edge of LDAC or, if LDAC is held low, on the rising edge of SYNC. The contents of the registers can be read using the readback function. Figure 88. AD5755-1-to-ADSP-BF527 SPORT Interface LAYOUT GUIDELINES Grounding Figure 87. Output Transient Voltage Protection Further protection can be provided using transient voltage suppressors (TVSs), also referred to as transorbs. These components are available as unidirectional suppressors, which protect against positive high voltage transients, and as bidirectional suppressors, which protect against both positive and negative high voltage transients. Transient voltage suppressors are available in a wide range of standoff and breakdown voltage ratings. The TVS must be sized with the lowest breakdown voltage possible while not conducting in the functional range of the current output. It is recommended that all field connected nodes be protected. The voltage output node can be protected with a similar circuit, where D2 and the transorb are connected to AVSS. For the voltage output node, the +VSENSE_x pin must also be protected with a large value series resistance to the transorb, such as 5 kΩ. In this way, the IOUT_x and VOUT_x pins can also be tied together and share the same protection circuitry. In any circuit where accuracy is important, careful consideration of the power supply and ground return layout helps to ensure the rated performance. The printed circuit board on which the AD5755-1 is mounted must be designed so that the analog and digital sections are separated and confined to certain areas of the board. If the AD5755-1 is in a system where multiple devices require an AGND-to-DGND connection, the connection must be made at one point only. The star ground point must be established as close as possible to the device. The GNDSWx and ground connection for the AVCC supply are referred to as PGND. PGND must be confined to certain areas of the board, and the PGND-to-AGND connection must be made at one point only. Supply Decoupling The AD5755-1 must 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 must have low effective series resistance (ESR) and low effective series inductance (ESL), 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. Rev. F | Page 48 of 51 Data Sheet AD5755-1 Traces GALVANICALLY ISOLATED INTERFACE The power supply lines of the AD5755-1 must use as large a trace as possible to provide low impedance paths and reduce the effects of glitches on the power supply line. Shield fast switching signals, such as clocks, with digital ground to prevent radiating noise to other parts of the board and never run them near the reference inputs. A ground line routed between the SDIN and SCLK lines helps reduce crosstalk between them (not required on a multilayer board that has a separate ground plane, but separating the lines helps). It is essential to minimize noise on the REFIN line because it couples through to the DAC output. 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. The Analog Devices iCoupler® products can provide voltage isolation in excess of 2.5 kV. The serial loading structure of the AD5755-1 makes it ideal for isolated interfaces because the number of interface lines is kept to a minimum. Figure 89 shows a 4-channel isolated interface to the AD5755-1 using an ADuM1400. For more information, visit www.analog.com. DC-to-DC Converters MICROCONTROLLER SERIAL DATA OUT VIB CONTROL OUT VIC VID ENCODE DECODE ENCODE DECODE ENCODE DECODE ENCODE DECODE *ADDITIONAL PINS OMITTED FOR CLARITY. Follow these guidelines when designing printed circuit boards (see Figure 81): VIA SYNC OUT To achieve high efficiency, good regulation, and stability, a welldesigned printed circuit board layout is required. ADuM1400* SERIAL CLOCK OUT Keep the low ESR input capacitor, CIN, close to AVCC and PGND. Keep the high current path from CIN through the inductor, LDCDC, to SWX and PGND as short as possible. Keep the high current path from CIN through LDCDC and the rectifier, DDCDC, to the output capacitor, CDCDC, as short as possible. Keep high current traces as short and as wide as possible. The path from CIN through the inductor, LDCDC, to SWX and PGND must be able to handle a minimum of 1 A. Place the compensation components as close as possible to COMPDCDC_x. Avoid routing high impedance traces near any node connected to SWx or near the inductor to prevent radiated noise injection. Rev. F | Page 49 of 51 Figure 89. Isolated Interface VOA VOB VOC VOD TO SCLK TO SDIN TO SYNC TO LDAC 09226-081 Avoid crossover of digital and analog signals. Traces on opposite sides of the board must run at right angles to each other. This reduces the effects of feedthrough on the board. A microstrip technique is by far the best but not always possible with a double-sided board. In this technique, the component side of the board is dedicated to ground plane, whereas signal traces are placed on the solder side. AD5755-1 Data Sheet the AD5700 HART modem output modulating the 4 mA to 20 mA analog current without affecting the dc level of the current. This circuit adheres to the HART physical layer specifications as defined by the HART Communication Foundation. INDUSTRIAL HART CAPABLE ANALOG OUTPUT APPLICATION—SHARED VOUT_X AND IOUT_X PIN Many industrial control applications have requirements for accurately controlled current output signals, and the AD5755-1 is ideal for such applications. Figure 90 shows the AD5755-1 in a circuit design for a HART-enabled output module, specifically for use in an industrial control application in which both the voltage output and current output are available—one at a time—on one pin, thus reducing the number of screw connections required. There is no conflict with tying the two output pins together because only the voltage output or the current output can be enabled at any one time. For transient overvoltage protection, a 24 V transient voltage suppressor (TVS) is placed on the IOUT/VOUT connection. For added protection, clamping diodes are connected from the IOUT_x/VOUT_x pin to the AVDD and AVSS power supply pins. A 5 kΩ current limiting resistor is also placed in series with the +VSENSE_x input. This is to limit the current to an acceptable level during a transient event. The recommended external band-pass filter for the AD5700 HART modem includes a 150 kΩ resistor, which limits current to a sufficiently low level to adhere to intrinsic safety requirements. In this case, the input has higher transient voltage protection and, therefore, does not require additional protection circuitry, even in the most demanding of industrial environments. The design provides for a HART-enabled current output, with the HART capability provided by the AD5700/AD5700-1 HART modem, the industry’s lowest power and smallest footprint HARTcompliant IC modem. For additional space-savings, the AD5700-1 offers a 0.5% precision internal oscillator. The HART_OUT signal from the AD5700 is attenuated and ac-coupled into the CHARTx pin of the AD5755-1. Such a configuration results in +15V +5V AVDD AVCC 10µF 0.1µF 2.7V TO 5.5V DVDD 10µF 0.1µF 10kΩ SW (×4) VBOOST (×4) VOUT B, C, D RESET IOUT B, C, D ALERT D2 CHART B, C, D RP FAULT IOUT A CLEAR D1 AD5755-1 SYNC MCU SCLK +VSENSE_A SDIN 4mA TO 20mA CURRENT LOOP D3 RL 500Ω 5kΩ SDO AVSS UART INTERFACE VOUTA LDAC DGND REFOUT REFIN CHART A AVSS GND 0.1µF 0.1µF 47nF C2 22nF C1 VCC TXD HART_OUT RXD RTS CD AD5700/AD5700-1 REF 1.2MΩ 1µF 300pF ADC_IP 150kΩ 1.2MΩ 150pF Figure 90. AD5755-1 in HART Configuration Rev. F | Page 50 of 51 09226-089 GND Data Sheet AD5755-1 OUTLINE DIMENSIONS 9.10 9.00 SQ 8.90 0.60 MAX 0.60 MAX 64 49 1 PIN 1 INDICATOR 48 PIN 1 INDICATOR 8.85 8.75 SQ 8.65 0.50 BSC 0.50 0.40 0.30 33 32 0.05 MAX 0.02 NOM 0.30 0.23 0.18 0.25 MIN FOR PROPER CONNECTION OF THE EXPOSED PAD, REFER TO THE PIN CONFIGURATION AND FUNCTION DESCRIPTIONS SECTION OF THIS DATA SHEET. 0.20 REF COMPLIANT TO JEDEC STANDARDS MO-220-VMMD-4 06-13-2012-C SEATING PLANE 16 7.50 REF 0.80 MAX 0.65 TYP 12° MAX 17 BOTTOM VIEW TOP VIEW 1.00 0.85 0.80 7.25 7.10 SQ 6.95 EXPOSED PAD Figure 91. 64-Lead Lead Frame Chip Scale Package [LFCSP_VQ] 9 mm × 9 mm Body, Very Thin Quad (CP-64-3) Dimensions shown in millimeters ORDERING GUIDE Model1 AD5755-1ACPZ AD5755-1ACPZ-REEL7 EVAL-AD5755-1SDZ 1 Resolution (Bits) 16 16 Temperature Range −40°C to +105°C −40°C to +105°C Z = RoHS Compliant Part. ©2011–2014 Analog Devices, Inc. All rights reserved. Trademarks and registered trademarks are the property of their respective owners. D09226-0-9/14(F) Rev. F | Page 51 of 51 Package Description 64-lead LFCSP_VQ 64-lead LFCSP_VQ Evaluation Board Package Option CP-64-3 CP-64-3