High Precision, Impedance, and Electrochemical Front End Data Sheet AD5940/AD5941 FEATURES Fast power-up and power-down analog blocks for duty Analog input cycling 16-bit ADC with both 800 kSPS and 1.6 MSPS options Programmable AFE sequencer to minimize workload of Voltage, current, and impedance measurement capability host controller Internal and external current and voltage channels 6 kB SRAM to preprogram AFE sequences Ultralow leakage switch matrix and input mux Ultra low power potentiostat channel: 6.5 A of current Input buffers and programmable gain amplifier consumption when powered on and all other blocks in Voltage DACs hibernate mode Dual output voltage DAC with an output range of 0.2 V Smart sensor synchronization and data collection to 2.4 V Cycle accurate control of sensor measurement 12-bit V output to bias potentiostat Sequencer controlled GPIOs BIAS0 6-bit V output to bias TIA On-chip peripherals ZERO0 Ultra low power: 1 A SPI serial input/output 1 high speed, 12-bit DAC Wake-up timer Output range to sensor: 607 mV Interrupt controller Programmable gain amplifier on output with gain Power settings of 2 and 0.05 2.8 V to 3.6 V supply Amplifiers, accelerators, and references 1.82 V input/output compliant 1 low power, low noise potentiostat amplifier suitable for Power-on reset potentiostat bias in electrochemical sensing Hibernate mode with low power DAC and potentiostat amplifier powered up to maintain sensor bias 1 low noise, low power TIA, suitable for measuring sensor Package and temperature range current output 3.6 mm 4.2 mm, 56-ball WLCSP 50 pA to 3 mA range 7 mm 7 mm, 48-lead LFCSP Programmable load and gain resistors for sensor output Fully specified for operating temperature range of 40C Analog hardware accelerators to +85C Digital waveform generator Receive filters APPLICATIONS Complex impedance measurement (DFT) engine Electrochemical measurements 1 high speed TIA to handle wide bandwidth input signals Electrochemical gas sensors from 0.015 Hz up to 200 kHz Potentiostat/amperometric/voltammetry/cyclic Digital waveform generator for generation of sinusoid and voltammetry trapezoid waveforms Bioimpedance applications 2.5 V and 1.82 V internal reference voltage sources Skin impedance System level power savings Body impedance Continuous glucose monitoring Battery impedance SIMPLIFIED BLOCK DIAGRAM POTENTIOSTAT: AMPLIFIER AND DAC WAVEFORM GENERATOR ADC FIFO AND MMR CURRENT CHANNELS DFT 16-BIT VOLTAGE ADC CHANNELS DIGITAL DATA FIFO INTERNAL FILTERS CHANNELS SLEEP/WAKEUP LDOs SEQUENCER TEMPERATURE TIMER CHANNEL INTERRUPTION VOLTAGE GPIOs SPI REFERENCES GENERATOR IMPEDANCE ENGINE AMPLIFIERS AND DAC Figure 1. Rev. B 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 One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A. rights of third parties that may result from its use. Specifications subject to change without notice. No Tel: 781.329.4700 20192020 Analog Devices, Inc. All rights reserved. license is granted by implication or otherwise under any patent or patent rights of Analog Devices. Technical Support www.analog.com Trademarks and registered trademarks are the property of their respective owners. 16778-201AD5940/AD5941 Data Sheet TABLE OF CONTENTS Features .............................................................................................. 1 Avoiding Incoherency Errors Between Excitation and Measurement Frequencies During Impedance Measurements Applications ....................................................................................... 1 ....................................................................................................... 43 Simplified Block Diagram ............................................................... 1 High Speed DAC Calibration Options .................................... 44 Revision History ............................................................................... 3 High Speed DAC Circuit Registers .......................................... 45 Functional Block Diagram .............................................................. 5 High Speed TIA Circuits ............................................................... 48 General Description ......................................................................... 6 High Speed TIA Configuration ................................................ 48 Specifications ..................................................................................... 7 High Speed TIA Circuit Registers ............................................ 50 ADC RMS Noise Specifications ............................................... 16 High Performance ADC Circuit ................................................... 52 SPI Timing Specifications ......................................................... 17 ADC Circuit Overview .............................................................. 52 Absolute Maximum Ratings .......................................................... 18 ADC Circuit Diagram ............................................................... 52 Thermal Resistance .................................................................... 18 ADC Circuit Features ................................................................ 53 ESD Caution ................................................................................ 18 ADC Circuit Operation ............................................................. 53 Pin Configuration and Function Descriptions ........................... 19 ADC Transfer Function ............................................................. 53 Typical Performance Characteristics ........................................... 22 ADC Low Power Current Input Channel ............................... 54 Reference Test Circuit ................................................................ 24 Selecting Inputs to ADC Mux .................................................. 54 Theory of Operation ...................................................................... 25 ADC Postprocessing .................................................................. 55 Configuration Registers ............................................................. 25 Internal Temperature Sensor Channel .................................... 55 Silicon Identification ...................................................................... 28 Sinc2 Filter (50 Hz/60 Hz Mains Filter) .................................. 55 Identification Registers .............................................................. 28 ADC Calibration ........................................................................ 55 System Initialization ....................................................................... 29 ADC Circuit Registers ............................................................... 56 Low Power DAC ............................................................................. 30 ADC Calibration Registers ....................................................... 62 Low Power DAC Switch Options ............................................. 30 ADC Digital Postprocessing Registers (Optional) ................ 68 Relationship Between the 12-Bit and 6-Bit Outputs .............. 31 ADC Statistics Registers ............................................................ 69 Low Power DAC Use Cases ....................................................... 31 Programmable Switch Matrix ....................................................... 70 Low Power DAC Circuit Registers ........................................... 32 Switch Descriptions ................................................................... 70 Low Power Potentiostat ................................................................. 35 Recommended Configuration in Hibernate Mode ............... 70 Low Power TIA ............................................................................... 36 Options for Controlling All Switches ...................................... 70 Low Power TIA Protection Diodes .......................................... 36 Programmable Switches Registers ........................................... 73 Using an External R ............................................................... 36 TIA Precision Voltage References ........................................................ 83 Recommended Switch Settings for Various Operating Modes High Power and Low Power Buffer Control Register ....................................................................................................... 36 BUFSENCON ............................................................................. 84 Low Power TIA Circuits Registers ........................................... 39 Sequencer ........................................................................................ 85 High Speed DAC Circuits .............................................................. 42 Sequencer Features ..................................................................... 85 High Speed DAC Output Signal Generation .......................... 42 Sequencer Overview .................................................................. 85 Power Modes of the High Speed DAC Core ........................... 42 Sequencer Commands ............................................................... 85 High Speed DAC Filter Options ............................................... 42 Sequencer Operation ................................................................. 87 High Speed DAC Output Attenuation Options ......................... 43 Sequencer and FIFO Registers ................................................. 89 High Speed DAC Excitation Amplifier ................................... 43 Waveform Generator...................................................................... 94 Coupling an AC Signal from the High Speed DAC to the DC Waveform Generator Features .................................................. 94 Level Set by the Low Power DAC ............................................. 43 Waveform Generator Operation .............................................. 94 Rev. B Page 2 of 133