Integrated Optical Module for
Smoke Detection
Data Sheet
ADPD188BI
FEATURES
GENERAL DESCRIPTION
3.8 mm × 5.0 mm × 0.9 mm module with integrated optical
components
1 blue LED, 1 IR LED, and 2 photodiodes
2 external inputs for other sensors (for example, carbon
monoxide (CO) and temperature)
The ADPD188BI is a complete photometric system for smoke
detection using optical dual wavelength technology. The module
integrates a highly efficient photometric front end, two light
emitting diodes (LEDs), and two photodiodes (PDs). These
items are housed in a custom package that prevents light from
going directly from the LED to the photodiode without first
entering the smoke detection chamber.
Three 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
Optimized SNR for signal limited cases
I2C or SPI communications
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 serial peripheral interface (SPI) port.
APPLICATIONS
Smoke detection
FUNCTIONAL BLOCK DIAGRAM
VDD1
VDD2
PDC
ADPD188BI
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
DATA
TIA_VREF
PDET2
PD4
14-BIT
ADC
CH4
TIME SLOT B
DATA
SDA
SCL
VLED1
AFE CONFIGURATION,
TIME SLOT A
TIA_VREF
VLED3
AFE CONFIGURATION,
TIME SLOT B
GPIO0
GPIO1
IR
BLUE
DIGITAL
INTERFACE
AND
LED1/DNC
CONTROL
LED1 DRIVER
LED3/DNC
LED2
LED3 DRIVER
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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