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.