1 Features

1• Transmitter:

– Supports Common Anode LED Configuration

– Dynamic Range: 100 dB

– 6-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:

– 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:

10 kΩ to 2 MΩ

– Dynamic Range: 100 dB

– Average Current Less Than 200 μA for PPG

Signal Acquisition

• Pulse Frequency: 10 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

• I2C Interface

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

• 2.6-mm × 1.6-mm DSBGA Package, 0.5-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)

• Heart-Rate Variability (HRV)

• Pulse Oximetry (SpO2 Measurement)

• VO2 Max

• Calorie Expenditure

3 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 I2C interface. The AFE also has a fullyintegrated

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.