New Content (2)
Application NotesAN-1557: Implementing the AD5940 and AD8233 in a Full Bioelectric System
Application NotesAN-1563: Optimizing the AD5940 for Electrochemical Measurements
Features and Benefits
- 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
- Dual output voltage DAC with an output range of 0.2 V to 2.4 V
- 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
- 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
- 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
- Cycle accurate control of sensor measurement
- Sequencer controlled GPIOs
- SPI serial input/output
- Wake-up timer
- Interrupt controller
- 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
- 3.6 mm × 4.2 mm, 56-ball WLCSP
- Fully specified for operating temperature range of −40°C to +85°C
The AD5940 is a high precision, low power analog front end (AFE) designed for portable applications that require high precision, electrochemical-based measurement techniques, such as amperometric, voltammetric, or impedance measurements. The AD5940 is designed for skin impedance and body impedance measurements, and works with the AD8233 AFE in a complete bioelectric or biopotential measurement system. The AD5940 is designed for electrochemical toxic gas sensing.
The AD5940 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, digital-to-analog converter (DAC), and a low power, low noise potentiostat. One output of the DAC controls the noninverting input of the potentiostat, and the other output controls the noninverting input of the transimpedance amplifier (TIA). This low power excitation loop is capable of generating signals from dc to 200 Hz.
The second excitation loop consists of a 12-bit DAC, referred to as the high speed DAC. This DAC is capable of generating high frequency excitation signals up to 200 kHz.
The AD5940 measurement channel features a 16-bit, 800 kSPS, multichannel successive approximation register (SAR) analog-to-digital converter (ADC) with input buffers, a built in antialias filter, and a programmable gain amplifier (PGA). An input mux in front of the ADC allows the user to select an input channel for measurement. These input channels include multiple external current inputs, 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 TIAs with programmable gain and load resistors for measuring different sensor types. The first TIA, referred to as the low power TIA, measures low bandwidth signals. The second TIA, referred to as the high speed TIA, measures high bandwidth signals up to 200 kHz.
An ultralow leakage, programmable switch matrix connects the sensor to the internal analog excitation and measurement blocks. This matrix provides an interface for connecting external RTIAs and calibration resistors. The matrix can also be used to multiplex multiple electronic measurement devices to the same wearable electrodes.
A precision 1.82 V 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 the 1.82 V and 2.5 V peripherals.
The AD5940 measurement blocks can be controlled via direct register writes through the serial peripheral interface (SPI) interface, or, alternatively, by using a preprogrammable sequencer, which provides autonomous control of the AFE chip. 6 kB of static random access memory (SRAM) is partitioned for a deep data first in, first out (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 the FIFO is full.
A number of general-purpose inputs/outputs (GPIOs) are available and are controlled using the AFE sequencer, which allows cycle accurate control of multiple external-sensor devices.
The AD5940 operates from a 2.8 V to 3.6 V supply and is specified over a temperature range of −40°C to +85°C. The AD5940 is packaged in a 56-lead, 3.6 mm × 4.2 mm WLCSP package.
- Electrochemical measurements
- Electrochemical gas sensors
- Bioimpedance applications
- Skin impedance
- Body impedance
- Continuous glucose monitoring
- Battery impedance
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Product Lifecycle 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.
Evaluation Kits (1)
The ADICUP3029 board is an Arduino form factor motherboard containing the ADuCM3029 microcontroller that runs sample firmware and communicates with the AD5940.
The EVAL-AD5940ARDZ board is designed to be versatile and enable different measurements, such as bioelectric, electrochemical, and potentiostat measurements. This is made possible by the expander board headers. The AD5940 kit contains two expander boards. The AD5940-BioElectric for bioimpedance and biopotential measurements, and the AD5940Sens2 for amperometric and impedance measurements.
The evaluation kit also includes custom USB to ECG cables to connect the kit to ECG/BIOZ simulator products. The kit should not be connected directly to the human body.
Features & Benefits
- Debug and programming capability for AD5940
- Evaluation capabilities for bioelectric and electrochemical measurements
- SensorPal GUI user guide for electrochemical and bioelectric measurements
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.
Sample & Buy
The USA list pricing shown is for BUDGETARY USE ONLY, shown in United States dollars (FOB USA per unit for the stated volume), and is subject to change. International prices may differ due to local duties, taxes, fees and exchange rates. For volume-specific price or delivery quotes, please contact your local Analog Devices, Inc. sales office or authorized distributor. Pricing displayed for Evaluation Boards and Kits is based on 1-piece pricing.