ISL29038 Datasheet, PDF (1/15 Pages) Xicor Inc. – Low Power Ambient Light and Proximity Sensor with Enhanced Infrared Rejection

Low Power Ambient Light and Proximity Sensor with
Enhanced Infrared Rejection
ISL29038
The ISL29038 is a low power Ambient Light Sensor (ALS) and
proximity (PROX) sensor. It has a built-in IR-LED driver for
proximity function. The ALS function measures the amount of
light (in the visible spectrum) incident on the ISL29038.
The ALS function has a programmable ambient IR-rejection,
which allows fine tuning of light source variations and is ideal
for light sensor applications under dark protective glass. The
ALS provides a 12-bit measurement. A passive optical filter
removes unwanted wavelengths (IR or Ultraviolet) to ensure
accurate ALS measurement.
The proximity function includes a new offset adjustment to
compensate for the IR light reflected off the inside of the
protective glass cover and back to the ISL29038 sensor. This
offset adjustment allows the sensor to compensate for these
internal reflections and preserve the dynamic range of the
proximity measurement.
The built-in current-driver pulses an external infrared LED at a
programmed current for 90µs. The infrared light that is
reflected and received by ISL29038 is digitized by an 8-bit
ADC. The proximity sensor also has a passive optical filter
designed to pass IR and reject visible wavelengths.
The ISL29038 provides a hardware pin to indicate an interrupt
event. The interrupt pin saves power as the host micro-controller
can ‘wake-up’ on an interrupt event and does not need to poll
the device for an interrupt event. The interrupt generator is
user configurable and provides several options for ALS and
PROX trigger configurations. The ISL29038 supports an
SMBus compatible I²C interface for configuration and control.
Features
• Ideal for applications under dark or tinted glass
• Enhanced ambient sunlight rejection to 40k Lux
• Programmable proximity sleep time between proximity
measurements optimizes power consumption
• Hardware interrupt - no polling required
• Programmable IR compensation to fine tune ALS
performance for various glass compositions
• Up to 4000 Lux, four selectable ALS ranges
• Programmable IR LED drive current to 250mA
• Operates from 2.25V to 3.63V V_DD
• Power Down I_DD, typical 0.2µA_DC
• Tiny 2.1x2.0x0.7 (mm) ODFN package
Applications
• Display dimming and adjustment
- Mobile devices: smart phones, PDA, GPS
- Computing: monitors, laptops, notebooks
- Picture frames, tablet-PCs, LCD-TV
• Object detection
- Touchscreen disabling
- Smart power-saving
VDD_IRLED
R₂
100
VDD_ANALOG
C₂
1µF
VDD_PULLUP
D₁ IRLED
C₁
1µF U1
1
2
3
4
GNDIR
AVDD
AGND
IRDR
8
7
INT
SDA
6
5
REXT SCL
SCL, SDA AND
INT PULLUPs
SMBus MASTER
INT
SDA
SCL
R₁ ^ISL29038
499k
R₁: 499k 1% RESISTOR
R₂: 100Ω 5% RESISTOR
C₁, C₂: 1µF CERAMIC 10V CAPACITOR
D₁: OSRAM SFH4650 INFRARED LED
FIGURE 1. TYPICAL APPLICATIONS CIRCUIT
100
90
80
70
60
50
40
30
20
10
0
0
250mA
125mA
62.5mA
31.25mA
20
40
60
80
18% GREY CARD PROXIMITY DISTANCE (mm)
FIGURE 2. PROXIMITY SENSITIVITY
October 12, 2012
1
FN7851.0
CAUTION: These devices are sensitive to electrostatic discharge; follow proper IC Handling Procedures.
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