1 Features

1• Supports signal acquisition of up to 24 phases

• Flexible allocation of 6 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 6 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

• I2C 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 AFE44I30 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 six switching lightemitting

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 I2C 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.