Ultra-small integrated AFE for multisensor wearable optical heart-rate monitoring

The Texas Instruments AFE4420 is an analogue front-end for optical bio-sensing applications, such as heart-rate monitoring and saturation of peripheral capillary oxygen. The device supports up to four switching LEDs and up to four photodiodes. Up to 16 signal phases can be defined, and the signal can be collected from each phase in a synchronised manner and stored in a 128-sample FIFO block. The FIFO can be read out with either an I2C or an SPI interface. The AFE also has a fully-integrated LED driver with 8-bit current control. The device has a high dynamic range transmit-and-receive circuitry that helps with the sensing of very small signal levels.