1 Features
• Supports signal acquisition of up to 12 phase sets
• Supports up to 4 LEDs, 3 PDs
• Flexible allocation of LEDs, PDs in each phase
• Simultaneous signal acquisition from different
sensors at different data rates
• Accurate, continuous PPG monitoring:
– Low current for continuous heart-rate
monitoring on a wearable device with a typical
value: 12 μA for the receiver
– Peak system SNR of 115 dB in 0.5-10 Hz band
enables high-accuracy SpO2 measurement
• Transmitter:
– 8-Bit Programmable LED current with range
adjustable from 25 mA to 250 mA
– Mode to fire two LEDs in parallel with
independent per-phase current control
– Programmable LED on-time per-phase
– Simultaneous support of 4 LEDs for SpO2,
Multi-Wavelength HRM
• Receiver:
– Supports 3 Time-Multiplexed PD Inputs
– 2 parallel receivers (2 sets of TIA/filter)
– Individual ambient offset subtraction DAC at
each TIA Input with 8-bit per-phase control and
range adjustable up to 255-μA
– Individual LED offset subtraction DAC at each
TIA input with 9-bit per-phase control and 64-
μA range
– Digital ambient subtraction at ADC output
– Noise filtering with programmable bandwidth
– Transimpedance gain: 3.7 kΩ to 1 MΩ
• Supports external clock or internal oscillator
• Option to acquire data synchronized with a system
clock
• Automatic cancellation of DC from Ambient, LED
• FIFO with 160-sample depth
• SPI™ interface/ I2C interface
• 1.9-mm × 1.8-mm DSBGA, 0.35-mm Pitch
• Supplies: Rx:1.7 - 1.9 V, Tx: 3-5.5 V

2 Applications
• Optical Heart-Rate Monitoring (HRM) for
wearables, hearables
• Heart-Rate Variability (HRV)
• Pulse Oximetry (SpO2) measurements

3 Description
The AFE4432 is an analog front-end for optical biosensing
applications, such as heart-rate monitoring
(HRM) and saturation of peripheral capillary oxygen
(SpO2). The device supports up to 4 switching lightemitting
diodes (LEDs) and up to three photodiodes
(PDs). The AFE has two LED drivers each with 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. Up to 12
signal phase sets can be defined, each phase
set comprising a combination of LED and Ambient
phases. Low noise offset DACs at the receiver inputs
can be automatically controlled to cancel DC from
Ambient and LED light. The current from the PDs in
each phase is converted into voltage by TIAs, filtered,
and then digitized using a common ADC. The ADC
code can be stored in a 160-sample FIFO block. The
FIFO can be read out using a SPI or I2C interface.