The AFE4420 is an analog front-end for optical bio-sensing applications, such as heart-rate monitoring (HRM) and saturation of peripheral capillary oxygen (SpO2). The device supports up to four switching light-emitting diodes (LEDs) and up to four photodiodes. Up to 16 signal phases can be defined and the signal can be acquired from each phase in a synchronized manner and stored in a 128-sample First in, First out (FIFO) block. The FIFO can be read out using either an I2C or a SPI interface. The AFE also has a fully integrated LED driver with an 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.