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 I
2
C 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
100
90
VDD_PULLUP
R
2
100
VDD_ANALOG
C
2
1µF
C
1
1µF
D
1
IRLED
SCL, SDA AND
INT PULLUPs
SMBus MASTER
INT
SDA
SCL
FULL SCALE RANGE (%)
VDD_IRLED
80
70
60
50
40
30
250mA
125mA
U1
1
8
GNDIR IRDR
2
7
AVDD
INT 6
3
SDA
AGND
4
5
SCL
REXT
62.5mA
R
1
ISL29038
499k
R
1
: 499k 1% RESISTOR
R
2
: 100Ω 5% RESISTOR
C
1
, C
2
: 1µF CERAMIC 10V CAPACITOR
D
1
: OSRAM SFH4650 INFRARED LED
31.25mA
20
10
0
0
20
40
60
18% GREY CARD PROXIMITY DISTANCE (mm)
80
FIGURE 1. TYPICAL APPLICATIONS CIRCUIT
FIGURE 2. PROXIMITY SENSITIVITY
October 12, 2012
FN7851.0
1
CAUTION: These devices are sensitive to electrostatic discharge; follow proper IC Handling Procedures.
1-888-INTERSIL or 1-888-468-3774
|
Copyright Intersil Americas Inc. 2012. All Rights Reserved
Intersil (and design) is a trademark owned by Intersil Corporation or one of its subsidiaries.
All other trademarks mentioned are the property of their respective owners.
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