AFE4900 Ultra-Low-Power Analog Front End

Texas Instruments AFE4900 Ultra-Low-Power Integrated Analog Front End (AFE) is designed for synchronized electrocardiogram (ECG), photoplethysmogram (PPG) signal acquisition. The synchronized PPG signal chain supports four switching light-emitting diodes (LEDs) and up to three photodiodes (PDs). A fully integrated LED driver controls the LEDs with a current of up to 200mA. The current from the photodiode is converted into voltage by the transimpedance amplifier (TIA) and then is digitized using an analog-to-digital converter (ADC). The same ADC interfaces to the ECG signal chain with an instrumentation amplifier (INA) and a programmable gain. The ECG input pins can be set using the right-leg drive (RLD) amplifier. The AFE4900 supports AC and DC lead-off detect schemes. A 128-sample first in, first out (FIFO) block stores the ADC codes from the PPG and ECG phases and reads out using either an I²C or a serial programming interface (SPI) interface.