Integrated Optical Module with Ambient
Light Rejection and Two LEDs
Data Sheet
ADPD188GG
FEATURES
GENERAL DESCRIPTION
3.8 mm × 5.0 mm × 0.9 mm module with integrated optical
components
2 green LEDs, 2 PDs with IR cut filter
2 external sensor inputs
3, 370 mA LED drivers
20-bit burst accumulator enabling 20 bits per sample period
On-board sample to sample accumulator enabling up to
27 bits per data read
Custom optical package made to work under a glass window
Optimized SNR for signal limited cases
I2C or SPI communications
The ADPD188GG is a complete photometric system designed to
measure optical signals from ambient light and from synchronous
reflected light emitting diode (LED) pulses. Synchronous measure-
ment offers best-in-class rejection of ambient light interference,
both dc and ac. The module integrates a highly efficient photo-
metric front end, two LEDs, and two photodiode (PD). All of
these items are housed in a custom package that prevents light
from going directly from the LED to the photodiode without first
entering the subject.
The front end of the application specific integrated circuit (ASIC)
consists of a control block, a 14-bit analog-to-digital converter
(ADC) with a 20-bit burst accumulator, and three flexible,
independently configurable LED drivers. The control circuitry
includes flexible LED signaling and synchronous detection.
The analog front end (AFE) features best-in-class rejection of
signal offset and corruption due to modulated interference
commonly caused by ambient light. The data output and
functional configuration occur over a 1.8 V I2C interface or a
serial peripheral interface (SPI) port.
APPLICATIONS
Optical heart rate monitoring
Reflective PPG measurement
CNIBP measurement
FUNCTIONAL BLOCK DIAGRAM
VDD1
VDD2
PDC
ADPD188GG
PD1
EXT_IN1
CH1
BPF
BPF
±1 INTEGRATOR
±1 INTEGRATOR
TIA_VREF
VREF
PD2
1µF
EXT_IN2
CH2
TIA_VREF
PDC
PDET1
PD3
CS
CH3
BPF
BPF
±1 INTEGRATOR
±1 INTEGRATOR
SCLK
MOSI
MISO
TIME SLOT A
TIA_VREF
DATA
PDET2
PD4
14-BIT
ADC
CH4
TIME SLOT B
DATA
SDA
SCL
VLED1
TIA_VREF
GREEN
GPIO0
GPIO1
DIGITAL
INTERFACE
AND
LED1/DNC
CONTROL
LED1 DRIVER
LED3 DRIVER
LED3
LED2
LED2 DRIVER
LGND
AGND
DGND
NOTES
1. DNC = DO NOT CONNECT. DO NOT CONNECT TO THIS PIN WHEN USING INTERNAL LEDs.
Figure 1.
Rev. B
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