Ultra-low-power integrated AFE for wearable optical, electrical biosensing

The Texas Instruments AFE4900 device is an AFE for synchronized ECG, PPG signal acquisition. The device can also be used for optical bio-sensing applications, such as HRM and SpO2. The PPG signal chain supports up to four switching LEDs and up to three photodiodes (PDs). The LEDs can be switched on using a fully integrated LED driver. The current from the photodiode is converted into voltage by the TIA and digitized using an ADC. The ECG signal chain has an INA with a programmable gain that interfaces to the same ADC. A RLD amplifier set can be used to the bias for the ECG input pins. AC and DC lead-off detect schemes are supported. The ADC codes from the PPG and ECG phases can be stored in a 128-sample FIFO block and read out using either an I2C or a SPI interface.