Analog front end for biological and chemical sensing

June 03, 2019 //By Julien Happich
analog front end
Analog Devices has released a novel electrochemical and impedance measurement front end that enables the next generation of vital sign monitoring devices and intelligent electrochemical sensors.

The AD5940 analog front end (AFE) incorporates both potentiostat and electrochemical impedance spectroscopy (EIS) functionality on a single chip, allowing for sensor measurement in both time and frequency domains. The device features integrated hardware accelerators for advanced sensor diagnostics, best-in-class low noise for accurate sensor measurements and is designed for wearable “always-on” applications.

Compared to traditional discrete solutions which pose limitations and require multiple ICs to achieve similar performance, ADI’s single chip solution offers advantages in terms of system accuracy and size flexibility to measure two-, three- and four-lead electrochemical sensors. The AFE chip can measure voltage, current and impedance.

It consists of two potentiostat loops, a low bandwidth loop with ability to generate AC signals up to 200 Hz and a high bandwidth loop with ability to generate AC signals up to 200kHz. The ultra-low power Potentiostat consumes 6.5uA in biased mode.

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 anti-alias filter (AAF), and a programmable gain amplifier (PGA). The ADC features 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 and voltage inputs, and internal voltage channels. The internal channels enable on chip diagnostic measurements of the internal supply voltages, die temperature, and reference voltages.

Analog Devices - www.analog.com


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