Analog front-end targets optical bio-sensing applications

This post is sponsored by Texas Instruments. The Texas Instruments (TI) AFE4404 is an analog front-end (AFE) for optical bio-sensing applications such as heart-rate monitoring (HRM) and saturation of peripheral capillary oxygen (SpO2). The device supports three switching light-emitting diodes (LEDs) and a single photodiode. The current from the photodiode is converted into voltage by the transimpedance amplifier (TIA) and digitized using an analog-to-digital converter (ADC). The ADC code can be read out using an I2C interface. The device has a fully-integrated LED driver with a 6-bit current control. It also has high dynamic range transmit and receive circuitry that helps with the sensing of very small signal levels.