Fully Integrated Photometric System
with Ambient Light Rejection
Data Sheet
Rev. SpB Document Feedback
Information furnished by Analog Devices is believed to be accurate and reliable. However, no
responsibility is assumed by Analog Devices for its use, nor for any infringements of patents or other
rights of third parties that may result from its use. Specifications subject to change without notice.
No license is granted by implication or otherwise under any patent or patent rights of Analog
Devices. Trademarks and registered trademarks are the property of their respective owners.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 781.329.4700 ©2014-2016 Analog Devices, Inc. All rights reserved.
Technical Support www.analog.com
FEATURES
2.8 mm × 5 mm module with integrated optical components
Red and infrared (IR) LEDs (ADPD142RI)
Red and green LEDs (ADPD142RG)
Photodiode
True dual channel 250 mA LED driver
Separate LED and AFE settings for each channel
Dual data registers for each LED return signal
14-bit ADC
20-bit burst accumulator enabling 20 bits per sample period
On-board sample to sample accumulator enabling up to
27 bits per data read
APPLICATIONS
Optical heart rate monitoring (HRM)
Reflective SpO
2
measurement
GENERAL DESCRIPTION
The ADPD142RG/ADPD142RI are complete photometric systems
designed to stimulate LEDs and measure the corresponding
optical return signals. These systems feature best-in-class
rejection of ambient light interference, both dc and ac. Each
module contains a highly efficient photometric front end, two
LEDs, and a photodiode. The front end consists of a control
block, a 14-bit analog-to-digital converter (ADC) with 20-bit
burst accumulator and two flexible, independently configurable
LED drivers. The analog front end (AFE) handles return data
from each LED on separate data paths, and with the option of
separate AFE settings. The data output and functional con-
figuration occur over a 1.8 V I
2
C interface. The control circuitry
includes flexible LED signaling and synchronous detection.
FUNCTIONAL BLOCK DIAGRAM
Figure 1.
For more information about the ADPD142RG/ADPD142RI, contact Analog Devices, Inc., at optical_sensors@analog.com.
12166-002
LED2
LED1
LED1 DRIVER
LED2 DRIVER
TIA
V
BIAS
AMBIENT
LIGHT
REJECTION
AFE: SIGNAL CONDITIONING
PHOTODIODE
ANALOG BLOCK
14-BIT
ADC
TIME SLOT A
DATA
TIME SLOT B
DATA
DIGITAL
INTERFACE
AND
CONTROL
AFE CONFIGURATION,
TIME SLOT A
AFE CONFIGURATION,
TIME SLOT B
LED1 LEVEL AND TIMING CONTROL
LED2 LEVEL AND TIMING CONTROL
LGND
VLED
SDA
SCL
INT
DGND
AGND
VREF
1µF
AVDD DVDD
LED1/NC
LED2/NC
ADPD142RG/ADPD142RI
AFE
GAIN
