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PDF ISL29147 Data sheet ( Hoja de datos )
| Número de pieza | ISL29147 | |
| Descripción | Low Power Ambient Light and Proximity Sensor | |
| Fabricantes | Intersil | |
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DATASHEET
Low Power Ambient Light and Proximity Sensor with
Enhanced Infrared Rejection
ISL29147
The ISL29147 is a low power Ambient Light Sensor (ALS) and
proximity (PROX) sensor. It has a built-in IR-LED for the
proximity function. The ALS function measures the amount of
light (in the visible spectrum) incident on the ISL29147.
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 ISL29147 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 the ISL29147 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 ISL29147 provides a hardware pin to indicate an interrupt
event. The interrupt pin saves power as the host microcontroller
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 ISL29147 supports an SMBus
compatible I2C interface for configuration and control.
Features
• Internal IR-LED and sensor for a complete solution
• 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
• Programmable IR LED drive current to 250mA
• Operates from 2.25V to 3.63V VDD
• Power-down IDD, typical 0.2µADC
• Tiny 2.40x4x1.2 (mm) optical co-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
R1
100Ω
C2
1µF
C1
1µF
VDD_PULLUP
SCL, SDA and
INT PULLUPs
5
6
7
8
U1
VDD
SCL
GND
LED+
SDA
INT
IRDR
LED-
4
3
2
1
ISL29147
SMBus MASTER
SCL
SDA
INT
R1: 100Ω 5% RESISTOR
C1, C2: 1µF CERAMIC 10V CAPACITOR
FIGURE 1. TYPICAL APPLICATIONS CIRCUIT
250
200
150
100
50
0
0
IRDR 250mA
IRDR 125mA
50 100
DISTANCE (mm)
FIGURE 2. PROXIMITY SENSITIVITY
150
January 6, 2015
FN8409.3
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 LLC 2013, 2014, 2015. 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.
1 page  
ISL29147
I2C Electrical Specifications For SCL and SDA unless otherwise noted, VDD = 3V, TA = +25°C (Note 8). (Continued)
SYMBOL
PARAMETER
TEST CONDITIONS
MIN
(Note 10)
MAX
TYP (Note 10) UNITS
tSU:DAT Data Set-up Time
100 ns
tR Rise Time of both SDA and SCL Signals
(Note 9)
20 + 0.1 x Cb
ns
tF Fall Time of both SDA and SCL Signals
(Note 9)
20 + 0.1 x Cb
ns
tSU:STO Set-up Time for STOP Condition
600 ns
tBUF Bus Free Time Between a STOP and START Condition
1300
ns
Cb Capacitive Load for Each Bus Line
400 pF
Rpull-up SDA and SCL System Bus Pull-Up Resistor
Maximum determined by tR and tF
1
kΩ
tVD;DAT Data Valid Time
0.9 µs
tVD:ACK Data Valid Acknowledge Time
0.9 µs
VnL Noise Margin at the LOW Level
0.1VDD
V
VnH Noise Margin at the HIGH Level
0.2VDD
V
NOTES:
6. Cover glass assumes fixed infrared/visible light transmissivity ratio of 10.
7. An 850nm infrared LED is used in production test for proximity/IR sensitivity testing.
8. All parameters in the I2C Electrical Specifications table are guaranteed by design and simulation.
9. Cb is the capacitance of the bus in pF.
10. Parameters with MIN and/or MAX limits are 100% tested at +25°C, unless otherwise specified. Temperature limits established by characterization
and are not production tested.
Submit Document Feedback
5
FN8409.3
January 6, 2015
5 Page 
ISL29147
Total Current Consumption
Total current consumption is the sum of IDD and IIRDR. The IRDR
pin sinks current and the average IRDR current is calculated by
using Equation 1. The IDD depends on voltage and the mode of
operation. For simplicity, Equation 1 ignores proximity ADC
conversion time since it is much smaller than the sleep time.
ALS IR Compensation
The ISL29147 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 ISL29147 under a glass cover experiences an
IR rich environment.
The on-chip ALS passive optical filter on the ISL29147 is designed
to block most of the IR incident on the ALS photo diodes. In
addition, the ISL29147 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 ISL29147 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 ISL29147
can provide light ‘leakage’ or ‘crosstalk’ from the IR LED by
reflection from the glass saturating the proximity sensor
measurement system (Figure 10).
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 ISL29147 proximity system
provides a user programmable proximity offset correction to
compensate for this reflection.
GLASS COVER
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 ISL29147 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 ISL29147 interrupts are designed to minimize host
micro-controller overhead of continuous polling. The ISL29147
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 Reg 0x09. Two 12-bit high and low threshold
values are written to these registers. The ISL29147 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 Reg 0x06 (PROX_LT and
PROX_HT) are 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 hysteresis scheme; when set to 1, proximity uses a
window comparator scheme.
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.
SENSOR
LED
PCB
FIGURE 10. PROXIMITY SET-UP HIGHLIGHTING CROSSTALK
REFLECTED FROM COVER GLASS
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FN8409.3
January 6, 2015
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