Overview

Features and Benefits

Analog input
  • 16-bit, 800 kSPS ADC
  • Voltage, current, and impedance measurement capability
    • Internal and external current and voltage channels
    • Ultralow leakage switch matrix and input mux
  • Input buffers and programmable gain amplifier
Voltage DACs
  • Dual output voltage DAC with an output range of 0.2 V to 2.4 V
12-bit VBIAS0 output to bias potentiostat
  • 6-bit VZERO0 output to bias TIA
  • Ultra low power: 1 μA
  • 1 high speed, 12-bit DAC
    • Output range to sensor: ±607 mV
    • Programmable gain amplifier on output with gain settings of 2 and 0.05
Amplifiers, accelerators, and references
  • 1 low power, low noise potentiostat amplifier suitable for potentiostat bias in electrochemical sensing
  • 1 low noise, low power TIA, suitable for measuring sensor current output
    • 50 pA to 3 mA range
    • Programmable load and gain resistors for sensor output
  • Analog hardware accelerators
    • Digital waveform generator
    • Receive filters
    • Complex impedance measurement (DFT) engine
  • 1 high speed TIA to handle wide bandwidth input signals from 0.015 Hz up to 200 kHz
  • Digital waveform generator for generation of sinusoid and trapezoid waveforms
  • 2.5 V and 1.82 V internal reference voltage sources
System level power savings
  • Fast power-up and power-down analog blocks for duty cycling
  • Programmable AFE sequencer to minimize workload of host controller
  • 6 kB SRAM to preprogram AFE sequences
  • Ultra low power potentiostat channel: 6.5 μA of current consumption when powered on and all other blocks in hibernate mode
Smart sensor synchronization and data collection
  • Cycle accurate control of sensor measurement
  • Sequencer controlled GPIOs
On-chip peripherals
  • SPI serial input/output
  • Wake-up timer
  • Interrupt controller
Power
  • 2.8 V to 3.6 V supply
  • 1.82 V input/output compliant
  • Power-on reset
  • Hibernate mode with low power DAC and potentiostat amplifier powered up to maintain sensor bias
Package and temperature range
  • 7 mm × 7 mm, 48-lead LFCSP
  • Fully specified for operating temperature range of −40°C to +85°C

Product Details

The AD5941 is a high precision, low power Analog Front End (AFE) designed for portable applications requiring high precision electrochemical based measurement techniques such as amperometric, voltametric or impedance measurements. The AD5941 is designed for skin impedance and body impedance measurements and is also designed to work with the AD8233 AFE in a complete bio-electric/bio-potential measurement system.

The AD5941 consists of two high precision excitation loops and one common measurement channel, which enables a wide capability of measurements of the sensor under test. The first excitation loop consists of an ultra-low power dual output string DAC and low power, low noise Potentiostat amplifier. One output of the DAC controls the non-inverting input of the Potentiostat amplifier and the other output controls the noninverting input of the TIA amplifier. This low power excitation loop is capable of generating DC to 200 Hz signals.

The second excitation loop consists of a 12-bit DAC, often referred to as the high speed DAC, is capable of generating high frequencies excitation signals up to 200 kHz.

The AD5941 measurement channel features a 16-bit, 800 kSPS multi-channel successive approximation register (SAR) ADC with input buffers, built-in anti-alias filter and Programmable gain amplifier (PGA). It has an input voltage range of ±1.35 V.  An input MUX before the ADC allows the user to select an input channel for measurement. These input channels include multiple external current inputs, multiple external voltage inputs and internal channels. The internal channels allow diagnostic measurements of the internal supply voltages, die temperature and reference voltages.

The current inputs include two Trans-impedance amplifiers (TIA) with programmable gain and load resistors for measuring different sensor types. The first TIA, referred to as LPTIA is designed for measuring low bandwidth signals. The second TIA, referred to as the high speed TIA is designed for measuring high bandwidth signals up to 200 kHz.

An ultra-low leakage programmable Switch Matrix is used for connecting the sensor to the internal analog excitation and measurement blocks. It provides an interface for connecting external TIA gain resistors and calibration resistors. It can also be employed for multiplexing multiple electronic measurement devices to the same wearable electrodes.

A precision 1.8V and 2.5 V on-chip reference source is available. The internal ADC and DAC circuits use this on-chip reference source to ensure low drift performance for these peripherals.

The AD5941 measurement blocks can be controlled via direct register writes via the SPI interface or alternatively using a pre-programmable sequencer, which provides autonomous control the AFE chip. 6 Kbyte of SRAM is partitioned for a deep Data FIFO and command FIFO. Measurement commands are stored in the command FIFO and measurement results are stored in the Data FIFO. A number of FIFO related interrupts are available to indicate when FIFO is full etc.

A number of GPIO’s are available which can be controlled using the AFE Sequencer. This allows for cycle accurate control of multiple external sensor devices via the sequencer.

The AD5941 operates from 2.7 V to 3.6 V supply and is specified over a temperature range of −40°C to +85°C. The AD5941 is packaged in a 48-lead 7 × 7 mm LFCSP package.

Application

  • Electrochemical measurements
  • Electrochemical gas sensors
  • Potentiostat/amperometric/voltammetry/cyclic
    • voltammetry
  • Bioimpedance applications
    • Skin impedance
    • Body impedance
  • Continuous glucose monitoring
  • Battery impedance

Product Lifecycle icon-recommended Recommended for New Designs

This product has been released to the market. The data sheet contains all final specifications and operating conditions. For new designs, ADI recommends utilization of these products.

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Reference Designs (1)

Design Resources

ADI has always placed the highest emphasis on delivering products that meet the maximum levels of quality and reliability. We achieve this by incorporating quality and reliability checks in every scope of product and process design, and in the manufacturing process as well.  "Zero defects" for shipped products is always our goal.

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Pricing displayed is based on 1-piece. The USA list pricing shown is for budgetary use only, shown in United States dollars (FOB USA per unit), and is subject to change. International prices may vary due to local duties, taxes, fees and exchange rates.