PPG Optical Sensor Module with Integrated
Red/IR Emitters and AFE
Data Sheet
ADPD144RI
FEATURES
GENERAL DESCRIPTION
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
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.
Low power
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).
Specifically designed for ultralow direct optical reflections
Independent AFE settings per channel
I2C data and control interface
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
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
FUNCTIONAL BLOCK DIAGRAM
VDD1
VDD2
ADPD144RI
ANALOG BLOCK
PD3
PD1
CH1
AMBIENT
LIGHT
AFE
GAIN
TIA
TIA
REJECTION
PD4
PD2
V
BIAS
CH2
AMBIENT
LIGHT
REJECTION
AFE
GAIN
AGND
VREF
V
BIAS
CH3
1µF
AMBIENT
LIGHT
VLED
TIME SLOT A
DATA
AFE
TIA
TIA
LEDs
GAIN
REJECTION
880nm
V
BIAS
14-BIT
ADC
SDA
SCL
CH4
TIME SLOT B
DATA
AMBIENT
LIGHT
REJECTION
AFE
GAIN
AFE CONFIGURATION,
TIME SLOT A
INT
660nm
AFE CONFIGURATION,
TIME SLOT B
V
DGND
BIAS
AFE: SIGNAL CONDITIONING
DIGITAL
INTERFACE
AND
CONTROL
LED2 DRIVER
LED1 DRIVER
LEDX2
LEDX1
LED2 LEVEL AND TIMING CONTROL
LED1 LEVEL AND TIMING CONTROL
LGND
Figure 1.
Rev. A
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