TI Ultra-small, Integrated AFE for Wearable, Optical Heart Rate Monitoring and Bio-Sensing
Analog front-end (AFE) for optical bio-sensing applications including heart-rate monitoring and saturation of peripheral capillary oxygen (Sp02).
- Pulse Frequency: 10 SPS to 1000 SPS
- Flexible Pulse Sequencing, Timing Control and Clock Options
- I2C Interface
- Supplies: Rx: 2 V to 3.6 V, Tx: 3 V to 5.25 V, IO: 1.8 V to 3.6 V
Product Description
The AFE4404 is an analog front-end (AFE) for optical bio-sensing applications, such as heart-rate monitoring (HRM) and saturation of peripheral capillary oxygen (SpO2). The device supports three switching light-emitting diodes (LEDs) and a single photodiode. The current from the photodiode is converted into voltage by the transimpedance amplifier (TIA) and digitized using an analog-to-digital converter (ADC). The ADC code can be read out using an I 2C interface. The AFE also has a fully-integrated LED driver with a 6-bit current control. The device has a high dynamic range transmit and receive circuitry that helps with the sensing of very small signal levels.
Applications include Optical Heart-Rate Monitoring (HRM), Heart-Rate Variability (HRV), Pulse Oximetry (SpO2 Measurement), VO2 Max and Calorie Expenditure.
Transmitter
Supports common anode LED configuration, dynamic range of 100dB, programmable LED on-time, 6-bit programmable LED Current to 50mA (extendable to 100 mA) and simultaneous support of 3 LEDs for optimized SPO2, HRM or multi-wavelength HRM.
Receiver
24-bit representation of the current input from a photodiode in twos complement format, individual DC offset subtraction DAC at TIA input for each LED and ambient phase, digital ambient subtraction at ADC output, programmable transimpedance gain of 10 kΩ to 2 MΩ and dynamic range 100dB.
Flexible pulse
Pulse frequency 10 SPS to 1,000 SPS with flexible pulse sequencing and timing control.