Ultra-low-power integrated AFE for optical bio-sensing applications

Texas Instruments AFE44S30 Ultra-Low-Power Integrated Analog Front End is designed for optical bio-sensing applications, including heart-rate monitoring and saturation of peripheral capillary oxygen.

The device supports up to eight switching light-emitting diodes and up to four photodiodes. Up to 24 signal phases can be defined, and the signal can be acquired from each phase in a synchronised manner. The current from the photodiode is converted into a voltage by the transimpedance amplifier and digitised using an ADC. The ADC code can be stored in a 128-sample First-In, First-Out block. The FIFO can be read out utilising an SPI interface.

The AFE also includes a fully-integrated LED driver with an 8-bit current control. The device has a high dynamic range transmit-and-receive circuitry that assists with the sensing of extremely small signal levels.