PPG Optical Sensor Module with Integrated

Red/IR Emitters and AFE

Data Sheet

ADPD144RI

Rev. A

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FEATURES

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

Specifically designed for ultralow direct optical reflections

Independent AFE settings per channel

Burst accumulator enabling 20 bits per sample period

Sample to sample accumulator enabling up to 27 bits per

data read

16-bit or 32-bit register or FIFO readout per channel

APPLICATIONS

Optical heart rate monitoring

Reflective SpO2 measurement

GENERAL DESCRIPTION

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-to-

noise 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

FUNCTIONAL BLOCK DIAGRAM

ANALOG BLOCK

TIME SLOT A

DATA

TIME SLOT B

DATA

AFE CONFIGURATION,

TIME SLOT A

AFE CONFIGURATION,

TIME SLOT B

SDA

SCL

INT

DGND

AGND

VREF

1µF

VDD1

VDD2

ADPD144RI

14-BIT

ADC

LED2 DRIVER

LED2 LEVEL AND TIMING CONTROL

LED1 DRIVER

LED1 LEVEL AND TIMING CONTROL

LGND

VLED

LEDX2

LEDX1

TIA

AMBIENT

LIGHT

REJECTION

AFE: SIGNAL CONDITIONING

AFE

GAIN

TIA

AMBIENT

LIGHT

REJECTION

AFE

GAIN

TIA

AMBIENT

LIGHT

REJECTION

AFE

GAIN

TIA

AMBIENT

LIGHT

REJECTION

AFE

GAIN

CH1

CH2

CH3

CH4

PD3

PD1

PD4

PD2

660nm

880nm

LEDs

DIGITAL

INTERFACE

AND

CONTROL

Figure 1.