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