Texas instrument af4432 integrated analog front-end

     The TI AFE4432 Integrated Analog Front-end (AFE) is used for optical biosensing applications such as heart rate monitoring (HRM) and peripheral capillary oxygen saturation (SpO(2)). The device supports up to four switched light emitting diodes (leds) and up to three photodiodes (PDS). The AFE has two LED drivers, each with 8-bit current control.

     The Texas Instruments AFE4432 features high dynamic range transmitting and receiving circuits that help sense very small signal levels. Up to 12 signal phase sets can be defined, each consisting of a combination of LED and ambient phases. The low noise offset dac at the receiver input can be automatically controlled to eliminate DC from ambient and LED lights. The current from pd in each phase is converted from TIAs to voltage, filtered, and then digitized using a typical ADC. ADC code can be stored in a 160-sample FIFO block. FIFO can be read using SPI or I(2)C interface.