A programmable low-power ADC interface for an ISFET sweat sensor used in a wearable multi-sensing system

An application specific integrated circuit (ASIC) named ANTIGONE (ANalog To dIGital cONvErter) was designed in AMS 0.35 mu m technology to interface with four Ion-sensitive field-effect transistor (ISFET) sensors and perform real-time monitoring of some biomarkers in human sweat. The non-invasive sweat sensing system is targeted for wearable personalized medicine and healthcare applications. The ASIC is based on the current-to-frequency converter (CFC) architecture and is able to perform measurements of multiple currents from a few pA up to 500 nA in time multiplexing. The ASIC is designed for low power consumption and interfaces with the sensors, biases them to the required voltages and sends the measured current values through a Serial Peripheral Interface (SPI) to a portable device.