1 Features

1• Accurate, Continuous Heart-Rate Monitoring:

– Up to 100-dB Dynamic Range for Accurate

Heart-Rate Detection

– Low Current for Continuous Operation on a

Wearable Device With a Typical Value:

– 30 μA for an LED, 25 μA for the Receiver

• Transmitter:

– 4 LEDs in Common Anode Configurations

– 8-Bit Programmable LED Current to 200 mA

– Mode to Fire Two LEDs in Parallel

– Programmable LED On-Time

– Simultaneous Support of 3 LEDs for Optimized

SpO2, HRM, or Multiwavelength HRM

– Average Current of 30 μA Adequate for a

Typical Heart-Rate Monitoring Scenario:

– 20-mA Setting, 60-μs Pulse Duration,

25-Hz Sampling Rate

• Receiver:

– Supports 3 Time-Multiplexed PD Inputs

– 24-Bit Representation of Current Input From

PD in Two's-Complement Format

– Individual DC Offset Subtraction DAC

(Up to ±127-μA Range) at TIA Input for Each

LED, Ambient

– Digital Ambient Subtraction at ADC Output

– Transimpedance Gain: 10 kΩ to 2 MΩ

– Noise Filtering With Programmable Bandwidth

– Receiver Operates at Approximately 1-μA/Hz

Sampling Rate (Example, 25 μA at 25 Hz)

– Hardware Power-Down Mode: Approximately

0-μA Current

• Flexible Pulse Sequencing and Timing Control

• Clocking Via External Clock or Internal Oscillator

• FIFO With 128-Sample Depth:

– Programmable Partitioning Across Phases

• Pin-Selectable I2C, SPI Interface

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

• 2.6-mm × 2.1-mm, 0.4-mm Pitch DSBGA Package

• Supplies:

– Tx: 3 V to 5.25 V

– Rx: 1.8 V to 1.9 V (LDO Bypass),

2.0 V to 3.6 V (LDO Enabled)

– IO: 1.7 V to Rx_SUP

2 Applications

• Optical Heart-Rate Monitoring (HRM) for

Wearables, Hearables

• Heart-Rate Variability (HRV)

• Pulse Oximetry (SpO2) Measurements

• Maximum Oxygen Consumption (VO2 Max)

3 Description

TheAFE4410is an analog front-end for optical

biosensing applications, such as heart rate monitoring

(HRM). The device supports a maximum of four

switching light-emitting diodes (LEDs) and a

maximum of three photodiodes (PDs). The electrical

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 is stored in a 128-sample first-in, first-out block

(FIFO) with programmable depth. The FIFO can be

read out using either an I2C interface or a serial

peripheral interface (SPI). The AFE also has a fully

integrated LED driver with 8-bit current control. The

device has high dynamic range transmit-and-receive

circuitry offering a dynamic range of up to 100 dB that

enables accurate heart ratesensing. The AFE

achieves extremely low current levels by operating an

ultralow power (ULP) mode set by using the

ENABLE_ULP register bit.