AD5940: Ultra‑Low‑Power, Dual‑Loop Impedance & Electrochemical Front End for Advanced Bio‑Sensing

Analog Devices introduces the AD5940, a cutting‑edge front‑end chip that delivers unmatched performance and power efficiency for impedance and electrochemical sensing. By integrating a dual‑loop potentiostat and a high‑resolution ADC, the AD5940 supports a full suite of electrochemical measurement techniques—including amperometry, voltammetry, and impedance spectroscopy—within a single, compact package.

Designed with healthcare applications in mind, the AD5940 excels in both skin‑impedance and whole‑body impedance measurements. It can also pair seamlessly with the AD8233 AFE to create a complete bioelectric/biopotential system, enabling clinicians and researchers to capture high‑quality physiological data.

The chip features two potentiostat loops: a low‑bandwidth loop that generates AC signals up to 200 Hz, and a high‑bandwidth loop capable of producing signals up to 200 kHz. Remarkably, the ultra‑low‑power potentiostat consumes only 6.5 µA in biased mode, making it ideal for battery‑powered or implantable devices.

Measurement capability is powered by a 16‑bit, 800 kSPS successive approximation register (SAR) ADC. The ADC includes built‑in anti‑alias filtering, a programmable gain amplifier, and an input range of ±1.35 V. An input multiplexer selects among external voltage and current inputs, as well as internal channels for on‑chip diagnostics—such as supply voltage, die temperature, and reference voltage monitoring.

Control is flexible: users can write directly to registers via the Serial Peripheral Interface (SPI) or leverage the built‑in sequencer for autonomous operation. The AD5940 contains 6 kB of SRAM, partitioned into a deep FIFO for data and a command memory for measurement scripts. Multiple FIFO‑related interrupts provide real‑time status feedback.