4-Channel, Low Noise, Low Power, 24-Bit, Sigma-Delta ADC with PGA and Reference Data Sheet AD7124-4 FEATURES Low-side power switch General-purpose outputs 3 power modes Multiple filter options RMS noise Internal temperature sensor Low power: 24 nV rms at 1.17 SPS, gain = 128 (255 A typical) Self and system calibration Mid power: 20 nV rms at 2.34 SPS, gain = 128 (355 A typical) Sensor burnout detection Full power: 23 nV rms at 9.4 SPS, gain = 128 (930 A typical) Automatic channel sequencer Up to 22 noise free bits in all power modes (gain = 1) Per channel configuration Output data rate Power supply: 2.7 V to 3.6 V and 1.8 V Full power: 9.38 SPS to 19,200 SPS Independent interface power supply Mid power: 2.34 SPS to 4800 SPS Power-down current: 5 A maximum Low power: 1.17 SPS to 2400 SPS Temperature range: 40C to +125C Rail-to-rail analog inputs for gains > 1 32-lead LFCSP/24-lead TSSOP Simultaneous 50 Hz/60 Hz rejection at 25 SPS (single cycle 3-wire or 4-wire serial interface settling) SPI, QSPI, MICROWIRE, and DSP compatible Diagnostic functions (which aid safe integrity level (SIL) Schmitt trigger on SCLK certification) ESD: 4 kV Crosspoint multiplexed analog inputs 4 differential/7 pseudo differential inputs APPLICATIONS Programmable gain (1 to 128) Temperature measurement Band gap reference with 10 ppm/C drift maximum (70 A) Pressure measurement Matched programmable excitation currents Industrial process control Internal clock oscillator Instrumentation On-chip bias voltage generator Smart transmitters FUNCTIONAL BLOCK DIAGRAM AV REGCAPA IOV DD REFOUT REFIN1(+) REFIN1() DD REGCAPD BANDGAP V REFIN2(+) BIAS AV 1.9V AV DD 1.8V REF SS REFIN2() AV LDO SS LDO CROSSPOINT MUX AV DD AIN0/IOUT/VBIAS REFERENCE BUFFERS AIN1/IOUT/VBIAS DOUT/RDY AIN2/IOUT/VBIAS/P1 BUF SERIAL VARIABLE 24-BIT BURNOUT INTERFACE AIN3/IOUT/VBIAS/P2 DIN PGA1 PGA2 DIGITAL - ADC DETECT AND FILTER AIN4/IOUT/VBIAS BUF CONTROL SCLK LOGIC AIN5/IOUT/VBIAS X-MUX CS AIN6/IOUT/VBIAS/REFIN2(+) ANALOG AV CHANNEL SS BUFFERS AIN7/IOUT/VBIAS/REFIN2() SEQUENCER SYNC GPOs TEMPERATURE AV DIAGNOSTICS DD SENSOR COMMUNICATIONS DIAGNOSTICS POWER SUPPLY EXCITATION INTERNAL PSW SIGNAL CHAIN CLK CURRENTS CLOCK POWER DIGITAL SWITCH AD7124-4 AV SS AV DGND SS Figure 1. 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Technical Support www.analog.com 13197-001AD7124-4 Data Sheet TABLE OF CONTENTS Features .............................................................................................. 1 Calibration................................................................................... 53 Applications ....................................................................................... 1 Span and Offset Limits .............................................................. 54 Functional Block Diagram .............................................................. 1 System Synchronization ............................................................ 54 Revision History ............................................................................... 3 Digital Filter .................................................................................... 55 4 General Description ......................................................................... 5 Sinc Filter ................................................................................... 55 3 Specifications ..................................................................................... 6 Sinc Filter ................................................................................... 57 4 1 Timing Characteristics .............................................................. 11 Fast Settling Mode (Sinc + Sinc Filter) .................................. 59 3 1 Absolute Maximum Ratings .......................................................... 14 Fast Settling Mode (Sinc + Sinc Filter) .................................. 61 Thermal Resistance .................................................................... 14 Post Filters ................................................................................... 63 ESD Caution ................................................................................ 14 Summary of Filter Options ....................................................... 66 Pin Configurations and Function Descriptions ......................... 15 Diagnostics ...................................................................................... 67 Typical Performance Characteristics ........................................... 18 Signal Chain Check .................................................................... 67 Terminology .................................................................................... 27 Reference Detect ......................................................................... 67 RMS Noise and Resolution............................................................ 28 Calibration, Conversion, and Saturation Errors .................... 67 Full Power Mode ......................................................................... 28 Overvoltage/Undervoltage Detection ..................................... 67 Mid Power Mode ........................................................................ 31 Power Supply Monitors ............................................................. 68 Low Power Mode ........................................................................ 34 LDO Monitoring ........................................................................ 68 Getting Started ................................................................................ 37 MCLK Counter ........................................................................... 68 Overview ...................................................................................... 37 SPI SCLK Counter...................................................................... 68 Power Supplies ............................................................................ 38 SPI Read/Write Errors ............................................................... 69 Digital Communication ............................................................. 38 SPI IGNORE Error ................................................................... 69 Configuration Overview ........................................................... 40 Checksum Protection ................................................................ 69 ADC Circuit Information .............................................................. 45 Memory Map Checksum Protection ....................................... 69 Analog Input Channel ............................................................... 45 ROM Checksum Protection...................................................... 70 External Impedance When Using a Gain of 1 ........................ 46 Burnout Currents ....................................................................... 71 Programmable Gain Array (PGA) ........................................... 47 Temperature Sensor ................................................................... 71 Reference ..................................................................................... 47 Grounding and Layout .................................................................. 72 Bipolar/Unipolar Configuration .............................................. 47 Applications Information .............................................................. 73 Data Output Coding .................................................................. 48 Temperature Measurement Using a Thermocouple .............. 73 Excitation Currents .................................................................... 48 Temperature Measurement Using an RTD ............................. 74 Bridge Power-Down Switch ...................................................... 49 Flowmeter .................................................................................... 76 Logic Outputs.............................................................................. 49 On-Chip Registers .......................................................................... 78 Bias Voltage Generator .............................................................. 49 Communications Register ......................................................... 79 Clock ............................................................................................ 49 Status Register ............................................................................. 79 Power Modes ............................................................................... 49 ADC CONTROL Register ....................................................... 80 Standby and Power-Down Modes ............................................ 49 Data Register ............................................................................... 82 Digital Interface .......................................................................... 50 IO CONTROL 1 Register........................................................ 82 DATA STATUS .......................................................................... 52 IO CONTROL 2 Register........................................................ 84 Serial Interface Reset (DOUT RDY DEL and CS EN Bits) 52 ID Register................................................................................... 84 Error Register .............................................................................. 84 Reset ............................................................................................. 52 Rev. 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