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PDF ISL29038 Data sheet ( Hoja de datos )
| Número de pieza | ISL29038 | |
| Descripción | Low Power Ambient Light and Proximity Sensor | |
| Fabricantes | Intersil | |
| Logotipo |  |
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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 VDD
• Power Down IDD, typical 0.2µADC
• 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
www.DataSheet.net/
- Touchscreen disabling
- Smart power-saving
VDD_IRLED
R2
100
VDD_ANALOG
C2
1µF
VDD_PULLUP
C1 D1 IRLED
1µF
1
2
3
4
U1
GNDIR
AVDD
AGND
REXT
IRDR
INT
SDA
SCL
8
7
6
5
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
18% GREY CARD PROXIMITY DISTANCE (mm)
FIGURE 2. PROXIMITY SENSITIVITY
80
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.
Datasheet pdf - http://www.DataSheet4U.co.kr/
1 page  
ISL29038
I2C Electrical Specifications
For SCL and SDA unless otherwise noted, VDD = 3V, TA = +25°C, REXT = 499kΩ 1% tolerance (Note 10). (Continued)
SYMBOL
PARAMETER
TEST CONDITIONS
MIN
TYP MAX
tR Rise Time of both SDA and SCL Signals
(Note 11)
20 + 0.1xCb
tF Fall Time of both SDA and SCL Signals
(Note 11)
20 + 0.1xCb
tSU:STO Set-up Time for STOP Condition
600
tBUF Bus Free Time Between a STOP and START Condition
1300
Cb Capacitive Load for Each Bus Line
Rpull-up SDA and SCL System Bus Pull-Up Resistor
Maximum determined by tR and tF
1
tVD;DAT Data Valid Time
tVD:ACK Data Valid Acknowledge Time
VnL Noise Margin at the LOW Level
0.1VDD
VnH Noise Margin at the HIGH Level
0.2VDD
NOTES:
7. Cover glass assumes fixed infrared/visible light transmissivity ratio of 10.
8. The LED light source irradiance is calibrated to produce the same ALS count as a fluorescent light source of the same Lux level.
9. An 850nm infrared LED is used in production test for proximity/IR sensitivity testing.
10. All parameters in I2C Electrical Specifications table are guaranteed by design and simulation.
11. Cb is the capacitance of the bus in pF.
400
0.9
0.9
UNITS
ns
ns
ns
ns
pF
kΩ
µs
µs
V
V
www.DataSheet.net/
FIGURE 4. I2C TIMING DIAGRAM
5
FN7851.0
October 12, 2012
Datasheet pdf - http://www.DataSheet4U.co.kr/
5 Page 
ISL29038
ALS IR Compensation
The ISL29038 is designed for operation under dark glass cover.
Glass or plastic covers can significantly attenuate visible light
and pass the Infrared light without much attenuation.
Consequently, the ISL29038 under a glass cover experiences an
IR rich environment.
The on-chip ALS passive optical filter on the ISL29038 is designed
to block most of the IR incident on the ALS photo diodes. In
addition, the ISL29038 provides a programmable active IR
compensation that subtracts residual IR still reaching the sensor.
The ALS_IR_COMP register (Reg 0x03[4:0]) allows fine tuning of
the residual infrared component from the ALS output.
The recommended procedure for determining ALS IR
compensation is as follows:
• Illuminate the ISL29038 based product with a light source
without IR, such as a white LED. Record the ALS measurement
and the Lux level.
• Illuminate the device with an IR LED and the White LED. Take
an ALS measurement and Lux level measurement.
• Adjust the ALS_IR_COMP register (Reg 0x03, bits 4:0) to
compensate for the IR contribution.
• Repeat steps above until the IR light source contribution to the
ALS measurement is under 10 percent assuming no change in
Lux level due to IR light source.
Proximity Offset
Systems built with a protective glass cover over the ISL29038
can provide light ‘leakage’ or ‘crosstalk’ from the IR LED by
reflection from the glass saturating the proximity sensor
measurement system (Figure 11).
Saturation can occur when the reflection from the glass with no
object in the proximity detection space exceeds the full scale of
the measurement system. The ISL29038 proximity system
provides a user programmable proximity offset correction to
compensate for this reflection.
GLASS COVER
SENSOR
LED
PCB
FIGURE 11. PROXIMITY SET-UP HIGHLIGHTING CROSSTALK
REFLECTED FROM COVER GLASS
The PROX_IR_COMP register (Reg 0x02[6:3]) applies a corrective
offset to the received signal prior to ADC conversion, which
allows the signal to be brought within the usable range of the
proximity measurement system.
Proximity Ambient Washout Detection
Optical proximity sensor can saturate when illuminated with
excessive ambient light. The ISL29038 provides a warning flag
when the proximity measurement may be erroneous due to
excessive ambient light. The PROX_WASH register (Reg 0x0D[0])
reports this condition.
Interrupts Events
The ISL29038 interrupts are designed to minimize host
micro-controller overhead of continuous polling. ISL29038 can
generate interrupts on the results of an ALS measurement or
proximity measurement.
The ALS interrupt event ALS_FLAG (Reg 0x04[3]) is governed by
Reg 0x07 through 0x09. Two-12 bit high and low threshold
values are written to these registers. The ISL29038 will set the
ALS interrupt flag if the ADC conversion count in Registers 0x0B
and 0x0C are outside the programmed thresholds. The
ALS_FLAG is cleared by writing a ‘0’ to Reg 0x04[3].
A proximity interrupt event (PROX_FLAG) is governed by the high
and low thresholds in Reg 0x05 and 0x06 (PROX_LT and
PROX_HT) and is indicated by Reg 0x04[7]. PROX_FLAG is set
when the measured proximity data is more than the higher
threshold. The proximity interrupt flag is cleared when the
proximity data is lower than the low proximity threshold or by
writing a ‘0’ to Reg 0x04[7].
The Proximity interrupt generation can be selected between
‘out-of-window’ threshold and hysteresis schemes. When the
PROX_INT_ALG register (Reg 0x02, Bit 7) is set to 0, proximity
uses a window comparator scheme; when set to 1, proximity
uses a hysteresis scheme.www.DataSheet.net/
In hysteresis mode, the interrupt event is generated if the
proximity ADC count is higher than the PROX_HT threshold and
the interrupt event is cleared when the proximity ADC count is
less than the PROX_LT threshold. The interrupt event flag can
also be cleared by writing a ‘0’ to Reg 0x04[7].
INTERRUPT PERSISTENCE
To minimize interrupt events due to ‘transient’ conditions, an
interrupt persistency option is available for both ALS and proximity
measurements. Persistency requires ‘X-consecutive’ interrupt flags
before the INT pin is driven low. Both ALS and PROX have their own
independent interrupt persistency options. ALS_PRST and
PROX_PRST configuration are controlled from Reg 0x04.
Power-Up and ‘Brown-Out’ Reset
The ISL29038 has an enhanced power-on-reset system. A
‘Brown-Out’ detector flag in Reg 0x04[4] informs the system that
the device has powered-up properly. This flag should be reset as
part of the initialization sequence.
A ‘Brown-Out’ condition is defined as an operating condition
when the power supply voltage is not within the specified limits.
During the brown-out period at power-up, the I2C interface and
the IR LED driver are inactive. Following brown-out, the I2C
interface is re-initialized and the configuration registers are set to
power-up default values. After power-up and during device
initialization, host should examine that the PWR_FAIL flag (Reg
11
FN7851.0
October 12, 2012
Datasheet pdf - http://www.DataSheet4U.co.kr/
11 Page | ||
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