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Texas Instruments AFE4460 Ultra-Small Integrated AFE

Texas Instruments AFE4460 Ultra-Small Integrated AFE is designed for optical biosensing applications, including heart-rate monitoring (HRM) and saturation of peripheral capillary oxygen (SpO2). The AFE4460 analog front-end supports up to 32 switching light emitting diodes (LEDs) and up to four photodiodes (PDs).

The TI AFE4460 Ultra-Small Integrated AFE features two LED drivers, each with 8-bit current control. The AFE offers a high dynamic range of transmit-and-receive circuitry that helps with sensing minimal signal levels. Additionally, the device can define up to 16 signal phase sets, with each phase set incorporating 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, which then can be read out using an SPI or I²C interface.

Features

Supports signal acquisition of up to 16 phase sets
Supports up to 32 LEDs, 4 PDs
Flexible allocation of LEDs and 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: 15μA for an LED, 15μA for the receiver
- Peak system SNR of 115dB
Transmitter:
- 8-Bit Programmable LED current with range adjustable from 25mA to 250mA
- Mode to fire two LEDs in parallel with independent per-phase current control
- Programmable LED on-time per-phase
- Simultaneous support of 32 LEDs for SpO2, multi-wavelength HRM, and spectroscopy

Receiver:
- Supports 4 Time-Multiplexed PD Inputs
- 4 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 255µA
- Individual LED offset subtraction DAC at each TIA input with 9-bit per-phase control and 64µA range
- Digital ambient subtraction at ADC output
- Noise filtering with programmable bandwidth
- 3.7kΩ to 1MΩ Transimpedance gain
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
2.6mm x 2.6mm DSBGA, 0.4mm Pitch
Supplies: Rx: 1.7V to 1.9V (LDO Bypass); 1.9V to 3.6V (LDO Enabled), Tx: 3V to 5.5V, IO: 1.7RX_SUP

Applications

Optical Heart-Rate Monitoring (HRM) for wearables, hearables
Heart-Rate Variability (HRV)

Pulse Oximetry (SpO2) measurements
Optical spectroscopy

Texas Instruments AFE4460 Ultra-Small Integrated AFE

Features

Applications

Block Diagram

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