PPG Optical Sensor Module with Integrated Red/IR Emitters and AFE

The ADPD144RI is a highly integrated, photometric front end optimized for photoplethysmography (PPG) detection of blood oxygenation (SpO2) by synchronous detection in red and infrared wavelengths. Synchronous measurement allows rejection of both dc and ac ambient light interference with extremely low power consumption.

The module combines highly efficient, light emitting diode (LED) emitters and a sensitive 4-channel, deep diffusion photodiode (PD1 to PD4) with a custom application specific integrated circuit (ASIC) in a compact package that provides optical isolation between the integrated LED emitters and the detection photodiodes to improve through tissue, signal-tonoise ratio (SNR).

The ASIC consists of a 4-channel analog front end (AFE) with two independently configurable datapaths with separate gain and filter settings, a 14-bit analog-to-digital converter (ADC) with a burst accumulator, two flexible, independently configurable, LED drivers, and a digital control block. The digital control block provides AFE and LED timing, signal processing, and communication. Data output and functional configuration occur over a 1.8 V I2C interface.

Applications

* Optical heart rate monitoring

* Reflective SpO2 measurement

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2.8 mm × 5.0 mm module with integrated optical components

* 660 nm LED, 880 nm IR LED, and photodiode

* Fully integrated AFE, ADC, LED drivers, and timing core

* Custom optical package for use under a glass window

* Programmable 2-channel, 8.5 mA to 370 mA LED drivers

* Provision to use external LED emitters

* Low power