1 Features

1• Transmitter:

– Supports Common Anode LED Configuration

– Dynamic Range: 100 dB

– 8-Bit Programmable LED Current to 50 mA

(Extendable to 100 mA)

– Programmable LED On-Time

– Simultaneous Support of 3 LEDs for Optimized

SpO2, HRM, or Multi-Wavelength HRM

• Receiver:

– Supports 2 Time-Multiplexed Photodiode

Inputs

– 24-Bit Representation of the Current Input from

the Photodiode in Twos Complement Format

– Individual DC Offset Subtraction DAC

(±15.75-μA Range) at TIA Input for Each LED,

Ambient

– Digital Ambient Subtraction at ADC Output

– Transimpedance Gain: 10 kΩ to 2 MΩ

– Dynamic Range: 100 dB

– Dynamic Power-Saving Mode to Reduce

Receiver Current to 200 μA

• Pulse Frequency: 5 SPS to 1000 SPS

• Flexible Pulse Sequencing and Timing Control

• Flexible Clock Options:

– External Clocking:

4-MHz to 60-MHz Input Clock

– Internal Clocking: 4-MHz Oscillator

• FIFO with 240 Sample Depth:

– Programmable Partitioning Across Phases

• I2C, SPI Interfaces: Selectable by Pin

• Operating Temperature Range: –20°C to +70°C

• 2.6-mm × 2.1-mm DSBGA, 0.4-mm Pitch

• Supplies: Rx: 2 V to 3.6 V, Tx: 3 V to 5.25 V,

IO: 1.8 V to 3.6 V

2 Applications

• Optical Heart-Rate Monitoring (HRM) for

Wearables, Hearables

• Heart-Rate Variability (HRV)

• Pulse Oximetry (SpO2) Measurements

• Maximum Oxygen Consumption (VO2 Max)

• Calorie Expenditure

3 Description

The AFE4405 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 up to two

photodiodes. 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

240-sample first in, first out (FIFO) block with

programmable depth. The FIFO depth can be

partitioned to accommodate the phases that must be

stored. The FIFO can be read out using either an I2C

or a SPI interface. The AFE also has a fullyintegrated

LED driver with an 8-bit current control.

The device has a high dynamic range transmit-andreceive

circuitry that helps with the sensing of very

small signal levels.

To request a full data sheet or other design

resources: request AFE4405