1 Features
1• Supports signal acquisition of up to 24 phases
• Flexible allocation of 8 LED, 4 PD in each phase
• Simultaneous signal acquisition from different
sensors at different data rates
• Accurate, continuous heart-rate monitoring:
– System SNR up to 108-dB at 16 μA PD current
– Low Current for Continuous Operation on a
Wearable Device with a Typical Value: 15 μA
for an LED, 20 μA for the Receiver
• Transmitter:
– Supports common anode LED configuration
– 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 8 LEDs for SpO2,
HRM, or multi-wavelength HRM
• Receiver:
– Supports 4 Time-Multiplexed Photodiode
Inputs
– 2 parallel receivers (two 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 5-bit per-phase control and 15.5-
μA range
– Close to 100 dB ambient rejection up to 10 Hz
– Noise filtering with programmable bandwidth
– Transimpedance Gain: 3.7 kΩ to 1 MΩ
• Supports external clock and internal oscillator
modes
• Option to acquire data synchronized with a system
master clock
• Automatic cancellation of DC from ambient, LED
• FIFO with 128-sample depth
• SPI interface
• 2.6-mm × 2.1-mm DSBGA, 0.4-mm pitch
• Supplies: Rx: 1.7 V-1.9 V (LDO bypass); 1.9 V-3.6
V (LDO enabled), Tx: 3 V-5.5 V, IO: 1.7-3.6 V

2 Applications
• Optical heart-rate monitoring (HRM) for
wearables, hearables
• Heart-rate variability (HRV)
• Pulse oximetry (SpO2) measurements

3 Description
The AFE44S30 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 eight switching
light-emitting diodes (LEDs) and up to four
photodiodes. Up to 24 signal phases can be defined
and the signal can be acquired from each phase in a
synchronized manner. 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 stored in a 128-sample First in, First out (FIFO)
block. The FIFO can be read out using a SPI
interface. The AFE also has a fully-integrated LED
driver with an 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.