描述 Description

The AFE4462 is an analog front-end for optical bio-sensing applications, such as heart-rate monitoring (HRM) and saturation of peripheral capillary oxygen (SpO2). The device supports up to 16 switching light-emitting diodes (LEDs) and up to four photodiodes (PDs). The AFE has two LED drivers each with 8-bit current control. The device has a high dynamic range transmit-and-receive circuitry that helps with the sensing of very small signal levels. Up to 16 signal phase sets can be defined, each phase set comprising a combination of LED and Ambient phases. Low noise offset DACs at the receiver inputs can be automatically controlled to cancel DC from Ambient and LED light. The current from each of the 4 PDs in each phase is converted into voltage by TIAs, filtered, and then digitized using a common ADC. The ADC code can be stored in a 256-sample FIFO block. The FIFO can be read out using a SPI or I2C interface.

特性 Features

Supports signal acquisition of up to 16 phase sets

Supports up to 16 LEDs, 4 PDs

Flexible allocation of LEDs, PDs in each phase

Simultaneous signal acquisition from different sensors at different data rates

Accurate, continuous PPG monitoring:

Low current for continuous heart-rate monitoring on a wearable device with a typical value: 15 μA for an LED, 15 μA for the receiver

Peak system SNR of 115 dB



Transmitter:

8-Bit Programmable LED current with range adjustable from 25 mA to 250 mA

Mode to fire two LEDs in parallel with independent per-phase current control

Programmable LED on-time per-phase

Simultaneous support of 16 LEDs for SpO2, Multi-Wavelength HRM, and Spectroscopy



Receiver:

Supports 4 Time-Multiplexed PD Inputs

2 parallel receivers (4 sets of TIA/filter)

Individual ambient offset subtraction DAC at each TIA Input with 8-bit per-phase control and range adjustable up to 255-μA

Individual LED offset subtraction DAC at each TIA input with 9-bit per-phase control and 64-μA range

Digital ambient subtraction at ADC output

Noise filtering with programmable bandwidth

Transimpedance gain: 3.7 kΩ to 1 MΩ



Supports external clock or internal oscillator

Option to acquire data synchronized with a system clock

Automatic cancellation of DC from Ambient, LED

FIFO with 256-sample depth

SPI? interface/ I2C interface

2.6-mm × 2.6-mm DSBGA, 0.4-mm Pitch

Supplies: Rx:1.7 - 1.9 V (LDO Bypass); 1.9 - 3.6 V (LDO Enabled), Tx: 3-5.5 V, IO: 1.7-RX_SUP