1
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
FIGURE 1. TYPICAL APPLICATIONS CIRCUIT FIGURE 2. PROXIMITY SENSITIVITY
5
6
7
8
4
3
2
1
VDD
SCL
GND
LED+
SDA
INT
IRDR
LED-
ISL29147
C1, C2: 1µF CERAMIC 10V CAPACITOR
INT
SDA
SCL
SMBus MASTER
VDD_IRLED
V
DD
C2
1µF
C1
1µF
VDD_PULLUP
U1
INT PULLUPs
SCL, SDA and
R1
100Ω
R1: 100Ω 5% RESISTOR
050 100 150
PROXIMITY COUNTS
DISTANCE (mm)
IRDR 125mA
IRDR 250mA
0
50
100
150
200
250
January 6, 2015
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CAUTION: These devices are sensitive to electrostatic discharge; follow proper IC Handling Procedures.
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Intersil (and design) is a trademark owned by Intersil Corporation or one of its subsidiaries.
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Block Diagram
Pin Configuration
ISL29147
(8 LD 2.40x4 (mm) OPTICAL CO-PACKAGE)
TOP VIEW
VDD
GND
SCL
IR PHOTODIODE
PHOTODIODE
7
6
5
FOSC
IREF
IRDR
ARRAY
ALS PHOTODIODE
AMPLIFIERS
(ALS AND IR)
ARRAY
DUAL CHANNEL
ADCs
2
INT
3
COMMAND
REGISTER
DATA
REGISTER
I2C
IR DRIVER
INTERRUPT
SDA
4
LED+
8
LED-
1
IRDR
SCL
SDA
INT
VDD
1
2
3
4
8
7
6
5
LED- LED+
GND
Pin Description
PIN# NAME DESCRIPTION
1 LED- Cathode of IR LED.
2 IRDR IR-LED Driver Sink - Connect to IR LED Cathode.
3INT
Active Low, Open-Drain Output.
4SDAI
2C Serial Data Input/Output.
5 VDD Positive supply: 2.25V to 3.63V.
6SCLI
2C Serial Clock Input.
7GNDGround.
8LED+Anode of IR LED.
Ordering Information
PART NUMBER
(Notes 1, 2, 3)
PART
MARKING
VDD RANGE
(V)
TEMP RANGE
(°C)
PACKAGE
(RoHS Compliant)
PKG.
DWG. #
ISL29147IROMZ-T7 N/A 2.25 to 3.63 -40 to +85 8 Ld Optical Co-package L8.2.40x4
ISL29147IROMZ-EVALZ Evaluation Board
NOTES:
1. Please refer to TB347 for details on reel specifications.
2. These Intersil Pb-free plastic packaged products employ special Pb-free material sets; molding compounds/die attach materials and NiPdAu plate - e4
termination finish, which is RoHS compliant and compatible with both SnPb and Pb-free soldering operations. Intersil Pb-free products are MSL
classified at Pb-free peak reflow temperatures that meet or exceed the Pb-free requirements of IPC/JEDEC J STD-020.
3. For Moisture Sensitivity Level (MSL), please see product information page for ISL29147. For more information on MSL, please see tech brief TB363.
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Absolute Maximum Ratings Thermal Information
VDD Supply Voltage between VDD and GND . . . . . . . . . . . . . . . . . . . . . .4.0V
I2C Bus Pin Voltage (SCL, SDA). . . . . . . . . . . . . . . . . . . . . . . . . -0.5V to 4.0V
I2C Bus Pin Current (SCL, SDA). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . <10mA
INT Pin Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -0.5V to 4.0V
INT Pin Current . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . <10mA
ESD Rating
Human Body Model (Tested per JESD22-A114E) (Note 4) . . . . . . . . 2kV
Thermal Resistance (Typical) JA (°C/W)
8 Ld Optical Co-package (Note 5). . . . . . . . 425
Maximum Die Temperature . . . . . . . . . . . . +90°C
Storage Temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .-40°C to +85°C
Operating Temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . . .-40°C to +85°C
Pb-Free Reflow Profile (*) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . see TB487
*Peak temperature during solder reflow +235°C max
CAUTION: Do not operate at or near the maximum ratings listed for extended periods of time. Exposure to such conditions may adversely impact product
reliability and result in failures not covered by warranty.
NOTES:
4. ESD on all pins is 2kV except IRDR, which is 1.5kV.
5. JA is measured in free air with the component mounted on a high effective thermal conductivity test board with “direct attach” features. See Tech
Brief TB379.
Electrical Specifications VDD = 3.0V, TA = +25°C.
PARAMETER DESCRIPTION TEST CONDITION
MIN
(Note 10)TYP
MAX
(Note 10)UNITS
INPUT POWER
VDD Power Supply Range 2.25 3.0 3.63 V
IDD_OFF Supply Current when Powered Down ALS_EN = 0; PROX_EN = 0 0.2 1.0 µA
IDD_NORM Supply Current for ALS+Prox in Sleep Time ALS_EN = 1; PROX_EN = 1 125 140 µA
IDD_PRX_SLP Supply Current for Prox in Sleep Time ALS_EN = 0; PROX_EN = 1 95 µA
IDD_ALS Supply Current for ALS ALS_EN = 1; PROX_EN = 0 95 µA
ADC (ALS and PROX)
tINTGR_ALS 12-bit ALS Conversion Time 80 95 110 ms
tINTGR_PROX 8-bit Prox Conversion Time 0.4 0.50 0.6 ms
DATAALS_0 ALS Result when Dark EAMBIENT = 0 Lux, 900 Lux range 1 Counts
DATAALS_F Full Scale ALS ADC Code EAMBIENT > selected range maximum Lux 4095 Counts
ΔDATA1
DATA
Output Variation Over Light Sources:
Fluorescent, Incandescent and Sunlight
Ambient light sensing, no cover glass
After programmable active IR compensation
(Note 6)
±10 %
ΔDATA2
DATA
Output Variation Over Light Sources:
Fluorescent, Incandescent and Sunlight
Ambient light sensing under cover glass
After programmable active IR compensation
(Note 6)
±10 %
Linearity ALS ADC Data Linearity 20% - 80% of full range ±5 %
DATAPROX_0 Prox Data without Object in Path 1Counts
DATAPROX_F Full Scale Prox ADC Code 255 Counts
ProxWASH Washout Bit Activation Level Norwood Solar Emulator 40k Lux
ProxOffsetMax Maximum PROX Offset, Referenced to
Proximity ADC Range
512 LSB
ProxOffsetInc Proximity Offset Adjust Increment
Referenced to Proximity ADC Range
27 LSB
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LED DRIVER (IRDR PIN)
trRise Time for IRDR Sink Current RLOAD = 15Ω at IRDR pin, 20% to 80% 25 ns
tfFall time for IRDR Sink Current RLOAD = 15Ω at IRDR pin, 80% to 20% 15 ns
IIRDR_0 IRDR Sink Current PROX_DR = 0; VIRDR = 0.5V 31.25 mA
IIRDR_1 IRDR Sink Current PROX_DR = 1; VIRDR = 0.5V 62.5 mA
IIRDR_2 IRDR Sink Current PROX_DR = 2; VIRDR = 0.5V 125 mA
IIRDR_3 IRDR Sink Current PROX_DR = 3; VIRDR = 0.5V 250 mA
IIRDR_LEAK IRDR Leakage Current PROX_EN = 0; VIRDR = 3.63V 0.001 1 µA
VIRDR IRDR Pin Voltage Compliance Register bit PROX_DR = 0 0.50 4.3 V
tPULSE IIRDR On Time Per PROX Reading 90 µs
Electrical Specifications VDD = 3.0V, TA = +25°C. (Continued)
PARAMETER DESCRIPTION TEST CONDITION
MIN
(Note 10)TYP
MAX
(Note 10)UNITS
IR-LED Specifications TA = +25°C.
SYMBOL PARAMETER TEST CONDITIONS
MIN
(Note 10)TYP
MAX
(Note 10)UNITS
VFIR-LED Forward Voltage IF = 100mA 1.8 V
VRIR-LED Reverse Voltage 5.5 V
λPIR-LED Peak Output Wavelength IF = 100mA 855 nm
ΔλIR-LED Spectral Half-Width IF = 100mA 30 nm
ΦEIR-LED Radiant Power IF = 100mA 38 mW
I2C Electrical Specifications For SCL and SDA unless otherwise noted, VDD = 3V, TA = +25°C (Note 8).
SYMBOL PARAMETER TEST CONDITIONS
MIN
(Note 10)TYP
MAX
(Note 10)UNITS
VI2CSupply Voltage Range for I2C Interface 1.7 3.63 V
fSCL SCL Clock Frequency 400 kHz
VIL SCL and SDA Input Low Voltage 0.55 V
VIH SCL and SDA Input High Voltage 1.25 V
Vhys Hysteresis of Schmitt Trigger Input 0.05VDD V
VOL Low-level Output Voltage (open-drain) at 4mA Sink
Current
0.4 V
IiInput Leakage for each SDA, SCL Pin -10 10 µA
tSP Pulse Width of Spikes that must be Suppressed by
the Input Filter
50 ns
tAA SCL Falling Edge to SDA Output Data Valid 900 ns
CiCapacitance for each SDA and SCL Pin 10 pF
tHD:STA Hold Time START Condition After this period, the first clock
pulse is generated
600 ns
tLOW LOW Period of the SCL Clock Measured at the 30% of VDD
crossing
1300 ns
tHIGH HIGH Period of the SCL Clock 600 ns
tSU:STA Set-up Time for a START Condition 600 ns
tHD:DAT Data Hold Time 30 ns
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tSU:DAT Data Set-up Time 100 ns
tRRise Time of both SDA and SCL Signals (Note 9) 20 + 0.1 x Cbns
tFFall Time of both SDA and SCL Signals (Note 9) 20 + 0.1 x Cbns
tSU:STO Set-up Time for STOP Condition 600 ns
tBUF Bus Free Time Between a STOP and START Condition 1300 ns
CbCapacitive Load for Each Bus Line 400 pF
Rpull-up SDA and SCL System Bus Pull-Up Resistor Maximum determined by tR and tF1kΩ
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.
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)TYP
MAX
(Note 10)UNITS
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ISL29147 Configuration and
Control
I2C Interface
The ISL29147 configuration and control is performed using the I2C
or SMBus. The ISL29147’s I2C interface slave address is internally
hard wired as 8’b1000100x, where x denotes the R/W bit.
Every I2C transaction begins with the master asserting a start
condition (SDA falling while SCL remains high). The first
transmitted byte is initiated by the master and includes 7
address bits and a R/W bit. The slave is responsible for pulling
SDA low during the ACK time after every transmitted byte.
Figure 4 shows a sample one-byte read. The I2C bus master
always drives the SCL (clock) line, while either the master or the
slave can drive the SDA (data) line.
Each I2C transaction ends with the master asserting a stop
condition (SDA rising while SCL remains high). For more
information about the I2C standard, consult the Philips™ I2C
specification documents.
Timing specifications are included in “I2C Electrical
Specifications” on page 4. The timing parameters are defined in
Figure 3.
The I2C interface on the ISL29147 supports single and multiple
byte read and write transfers using the random-read/write
protocol. The ISL29147 does not support I2C ‘Repeat Start’
protocol.
NOTE: In most system implementations, the ISL29147 is connected to a
single I2C master with one or more slave devices, consequently, absence
of the “Repeat Start” function does not adversely affect I2C bus system
performance.
FIGURE 3. I2C TIMING DIAGRAM
FIGURE 4. I2C DRIVER TIMING DIAGRAM FOR MASTER AND SLAVE CONNECTED TO COMMON BUS
START WA A
A6 A5 A4 A3 A2 A1 A0 W A R7 R6 R5 R4 R3 R2 R1 R0 A A6 A5 A4 A3 A2 A1 A0 W A
A A AD7D6D5D4D3D2D1D0
1357 1357 123456 9 2 4 6
STOP START
SDA DRIVEN BY MASTER
DEVICE ADDRESS
SDA DRIVEN BY ISL29147
DATA BYTE0REGISTER ADDRESS
SLAVE
DEVICE ADDRESS
I2C DATA
SDA DRIVEN BY MASTER
SDA DRIVEN BY MASTER
2468
924689 78135789
I2C SDA
I2C SDA
I2C CLK
MASTER
(ISL29147)
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Typical Performance Curves
FIGURE 5. PROXIMITY SENSITIVITY (Note 11)FIGURE 6. ALS SENSITIVITY (Note 12)
FIGURE 7. PROXIMITY AMBIENT LIGHT REJECTION (Note 13) FIGURE 8. ALS ANGULAR SENSITIVITY (Note 14)
NOTES:
11. Figure 5 shows ISL29147 Proximity distance sweeps with different IRDR LED current settings using an 18% Grey card reflector.
12. Figure 6 shows ISL29147 Ambient Light Sensor Spectral response when compared to a theoretical CIE 1924 Photopic curve. The ‘Blue’ line shows
the ISL29147 response and the ‘Red’ line depicts the CIE 1924 Photopic curve.
13. Figure 7 shows the ISL29147 Proximity Ambient Light Rejection using a Norwood Solar Emulator. At 40k Lux ambient light level, the Proximity
Washout Count (Reg 0x0D[7:1]) is 127 indicating a saturation in Proximity Signal processing path. The Proximity Washout bit 0x0D[0] is active at
approximately 90% of the maximum level. At 10% initial PROX count (due to optical leakage from IR LED to the ISL29147), the PROX data error is
under 2%. At 50% initial PROX count (severe optical leakage), the PROX data error is about 7%.
14. Figure 8 shows the Ambient Light Sensor Angular Sensitivity of the ISL29147 using a white LED light source.
0
50
100
150
200
250
0 50 100 150
PROXIMITY COUNTS
DISTANCE (mm)
IRDR 250mA
IRDR 125mA
0
10
20
30
40
50
60
70
80
90
100
300
350
400
450
500
550
600
650
700
750
800
850
900
950
1000
1050
1100
FSR (%)
WAVELENGTH (nm)
RANGE: 900 Lux
ALS RESPONSE (BLUE)
CIE 1924 PHOTOPIC CURVE
AMBIENT LIGHT LEVEL (LUX)
0 8k 16k 24k 32k 40k
15
10
5
50%
10%
0
VALUE CHANGE (% FSR)
0
10
20
30
40
50
60
70
80
90
100
0153045607590
ANGLE (°)
-90 -75 -60 -45 -30 -15
ALS RESPONSE (1% )
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ISL29147 Register Set
TABLE 1. ISL29147 CONFIGURATION AND CONTROL REGISTERS
ADDRESS
(HEX)
REGISTER
NAME
POWER-ON
DEFAULT
REGISTER
ACCESS
BIT
FIELDS
FUNCTION
NAME/VALUE FUNCTION
0x00 Device ID b11000xxx RO [7:0] Device Identification
[7:3] [11000] ISL29147 Device ID
[2:0] [XXX] Reserved
0x01 Config0 0x00 RW [7:0] Proximity Configuration
[7:6] Reserved
RW [5] PROX_EN Proximity Enable/Disable
[1] Enable
[0] Disable
RW [4:2] PROX_SLP Proximity Sleep Time Select
[000] 400ms
[001] 100ms
[010] 50ms
[011] 25ms
[100] 12.5ms
[101] 6.25ms
[110] 3.125ms
[111] 0ms
RW [1:0] IRDR_DRV IR LED Current
[00] 31.25mA
[01] 62.5mA
[10] 125mA
[11] 250mA
0x02 Config1 0x00 RW [7:0] Proximity/ALS Configuration
RW [7] INT_ALG Interrupt Algorithm
[0] Hysteresis Window
[1] Window Comparator
RW [6:3] PROX_OFFSET Proximity Offset Compensation
RW [2] ALS_EN Ambient Light Sensing Enable/Disable
[1] Enable
[0] Disable
RW [1:0] ALS_RANGE Ambient Light Sensor Range Select
[00] 56.25 Lux
[01] 112.5 Lux
[10] 900 Lux
[11] 1800 Lux
0x03 Config2 0x00 RW [7:0] ALS_IR_COMP Ambient Light Sensor IR Compensation
RW [7:5] Reserved
RW [4:0] ALSIRComp ALS Infra Red Compensation
(Unsigned Binary)
0x04 INTConfig 0x10 RW [7:0] INTConfig Interrupt Configuration, Status and Control
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RO [7] PROX_INT_FLG Proximity Interrupt Flag
[1] Proximity Interrupt Event
[0] No Proximity Interrupt Event
RW [6:5] PROX_PRST Proximity Interrupt Reporting Persistency
[00] INT after 1 Proximity Flag Event
[01] INT after 2 Consecutive Proximity Flag Event
[10] INT after 4 Consecutive Proximity Flag Event
[11] INT after 8 Consecutive Proximity Flag Event
RO [4] PWR_FAIL Power Failure (Brown-out) Alarm
[1] Brown-Out Detected
[0] Normal Operation
RO [3] ALS_INT_FLG Ambient Light Sensor Interrupt Flag
[1] ALS Interrupt Flag Event
[0] No ALS Interrupt Flag Event
RW [2:1] ALS_INT_PRST ALS Interrupt Reporting Persistency
[00] INT after 1 ALS Flag Event
[01] INT after 2 Consecutive ALS Flag Event
[10] INT after 4 Consecutive ALS Flag Event
[11] INT after 8 Consecutive ALS Flag Event
RW [0] INT_CFG Interrupt Output (Pin) Configuration
[1] Interrupt if ALS and PROX Event
[0] Interrupt if ALS or PROX Event
0x05 PROX_INT_TL 0x00 RW [7:0] PROX_INT_TL Proximity Interrupt LOW threshold
0x06 PROX_INT_TH 0xFF RW [7:0] PROX_INT_TH Proximity Interrupt HIGH threshold
0x07 ALS_INT_TL 0x00 RW [7:0] ALS_INT_TL1 ALS Interrupt LOW threshold bit[11:4]
0x08 ALS_INT_TLH 0x0F RW [7:0] ALS Interrupt LOW/HIGH threshold bits
[7:4] ALS_INT_TL0 ALS Interrupt LOW threshold bit[3:0]
[3:0] ALS_INT_TH1 ALS Interrupt HIGH threshold bit[11:8]
0x09 ALS_INT_TH 0xFF RW [7:0] ALS_INT_TH0 ALS Interrupt HIGH threshold bit[7:0]
0x0A PROX_DATA RO [7:0] PROX_DATA Proximity Data (Unsigned Binary)
0x0B ALS_DATA_HB RO [7:0] ALS_DATA_HB ALS Data HIGH Byte
[7:4] Set to 0000
[3:0] ALS Data Bit[11:8]
0x0C ALS_DATA_LB RO [7:0] ALS_DATA_LB ALS Data Bit[7:0]
0x0D PROX_AMBIR RO [7:0] PROX_AMBIR Proximity Mode Ambient IR Measurement
[7:1] Proximity Mode Ambient IR Component
RO [0] PROX_WASH Proximity Washout Status
[1] Proximity Washout Detected
[0] Normal Proximity Operation
0x0E Config3 0x00 [7:0] SoftReset Software Reset
0x38 Initiate Soft Reset
0x00 Normal operation
TABLE 1. ISL29147 CONFIGURATION AND CONTROL REGISTERS (Continued)
ADDRESS
(HEX)
REGISTER
NAME
POWER-ON
DEFAULT
REGISTER
ACCESS
BIT
FIELDS
FUNCTION
NAME/VALUE FUNCTION
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Registers 0x01 and 0x02 are used to configure the primary
proximity and ALS parameters. Register 0x03 is used for optimizing
IR compensation in ALS measurements. A procedure to optimize IR
compensation is described in “ALS IR Compensation” on page 11.
Register 0x04 is the Interrupt Configuration and Status Register,
they are used primarily to indicate interrupt events from proximity
and ALS measurements. A PWR_FAIL bit to indicate a ‘Brown-Out’
event is available and is set in case of a power supply interruption. A
‘Brown-Out’ event does not generate a hardware interrupt. The host
microcontroller must clear this bit by writing a ‘0’ to Reg 0x04[4].
Register 0x04 is also used to configure ALS and Proximity
interrupt persistency and the operation of the INT pin.
Registers 0x05 and 0x06 are used to set the proximity ‘LOW’ and
‘HIGH’ threshold for proximity interrupt event generation.
Registers 0x07, 0x08 and 0x09 are used to set the ALS ‘LOW’
and ‘HIGH’ threshold. Two 12-bit numbers span three address
locations as shown in Table 1.
Data registers 0x0A holds result of proximity conversion. The
proximity result should be validated by ‘Washout’ bit in
Reg 0x0D[0]. Registers 0x0B and 0x0C holds result of an ALS
measurement.
The ALS data is 12 bits wide. Least Significant Byte of the ALS
data is available at address 0x0C and Most Significant Byte
(MSB) of ALS data is available at address 0x0B. The MSB is right
justified, i.e., the upper nibble is always zero and lower nibble
contains four data bits.
Register 0x0D[7:1] contains ambient IR measurement in proximity
measurement phase. This measurement is for detecting ambient
Wash out condition, which is indicated by Reg 0x0D[0] being ‘HIGH’.
Proximity ‘Washout’ is described in “Proximity Ambient Washout
Detection” on page 11.
A software reset can be initiated by writing 0x38 to Register
0x0E.
ISL29147 Operation
Photodiodes and ADCs
The ISL29147 contains two photodiode arrays, which convert
photons (light) into current. The ALS photodiodes are designed to
mimic the human eye’s wavelength response curve to visible light.
The ALS photodiodes’ current output is digitized by a 12-bit ADC.
The ALS ADC output is accessed by reading from Reg 0x0B and
0x0C when the ADC conversion is completed.
The ALS ADC converter uses a charge-balancing architecture.
Charge-balancing is best suited for converting small current signals
in the presence of periodic AC noise. The ISL29147 targets an
integration time of 90ms, which can vary ±15% from nominal. The
ALS integration time is intended to minimize 60Hz flicker.
The proximity sensor uses an 8-bit ADC, which operates in a
similar fashion. The IRDR pin drives (pulses) an infrared LED, the
emitted IR reflects off an object back into the ISL29147, and the
photo diodes convert the reflected IR to a current signal in
0.5ms. The ADC subtracts the IR reading before and after the
LED is driven to remove ambient IR contribution.
The ALS runs continuously with new data available every 90ms.
The proximity sensor runs continuously with a time between
conversions controlled by PROX_SLP (Reg 0x01[6:4]).
Ambient Light Sensing
The ISL29147 is set for ambient light sensing when Register bit
ALS_EN = 1. Four measurement ranges from 56.25 Lux to 1800 Lux
are available. The ALS measurement range is configured via
Reg 0x02[1:0].
Proximity Sensing
When proximity sensing is enabled (PROX_EN = 1), the external
IR LED is driven for 90µs by the built-in IR LED driver through the
IRDR pin.
The IR LED current depends on PROX_DRV (Reg 0x01[1:0]). Drive
current settings are as shown in Table 1. The IR LED drive is in
high impedance state when not active.
When the IR from the LED reaches an object and gets reflected
back to the ISL29147, the reflected IR light is converted into a
current. This current is converted to digital data using an 8-bit
ADC. The proximity measurement takes 0.5ms for one
conversion including the 90μs LED drive time. The period
between proximity measurements is determined by PROX_SLP
(sleep time) in Reg 0x01[4:2].
Average LED driving current consumption is given by Equation 1.
A typical IRDR scheme is 250mA pulses every 400ms, averaging
about 56μA DC.
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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.
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.
ISL29147
12 FN8409.3
January 6, 2015
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Power-Up and ‘Brown-Out’ Reset
The ISL29147 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.
To prevent this condition we recommend the power supply slew
rate to be greater than 0.5 V/ms.
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 reinitialized 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 0x04[4]) is set and then clear the flag by writing ‘0’ to
Reg 0x04[4].
Following power-up, a ‘Brown-Out’ condition, if detected, is
reported by PWR_FAIL flag by Reg 0x04[4]. Device configuration
registers are not set to their power-up default after ‘Brown-Out’.
PWR_FAIL flag should be periodically monitored to detect post
power-up power supply interruption.
Power-Down
Setting ALS_EN (Reg 0x02[2]) and PROX_EN (Reg 0x01[5]) to ‘0’
puts the ISL29147 into a power-down state with power supply
current dropping to less than 1µA. All configuration registers are
maintained in power-down mode.
Soft Reset
A software reset to ISL29147 can be initiated by writing 0x38 to
Reg 0x0E. Following reset, all configuration registers are set to
their default power-up state. After soft reset, the ISL29147
defaults to the power-down configuration.
ALS Data Count Read Out
A two byte I2C read from ALS_DATA_HB outputs MSB 1st data on
SDA. This data is LSB justified with a zero fill for unused bits.
NOTE: The MSB byte address precedes the LSB byte address. The ALS
count is 256*(ALS_DATA_HB) + ALS_DATA_LB.
Proximity Detection of Various Objects
The Proximity sensing relies on the amount of IR reflected back
from objects. A perfect black object would absorb all incident light
and reflect no photons. The ISL29147 is sensitive enough to detect
black ESD foam, which reflects only 1% of IR. Blonde hair typically
reflects more than brown hair and skin tissue is more reflective
than human hair.
IR penetrates into the skin and is reflected from within. As a result,
the proximity count generally peaks at contact and monotonically
decreases as skin moves away. The reflective characteristics of
skin are very different from that of an inanimate object such as
paper.
Typical Application Circuit
A typical application circuit for the ISL29147 is shown in
Figure 11. The ISL29147’s I2C address is internally hard wired as
‘1000100x’, with x representing the R/W bit. The device can be
connected to a system’s I2C bus together with other I2C
compliant devices. It is important to ensure that there is no
address conflict with other I2C devices on the bus.
The SCL, SDA and INT pins on the ISL29147 are open drain and
require pull-up resistors for proper system operation. Values of
the pull-up resistors is system dependent and can range from
2.2k to 10k depending upon the number of I2C devices on the
bus.
The proximity sensing system can be powered using a dual power
supply or using a single power supply. In dual supply
configuration, the IR LED and the ISL29147 are powered from
separate power supplies. The VDD IRLED can range from 2.25V
to 5.0V and the VDD can range from 2.25V to 3.63V. In dual
supply configuration, resistor R1 should not be installed.
In single supply configuration, the IR LED and the ISL29147 are
powered from the same power source. The VDD_IRLED can range
from 2.25V to 3.63V and the VDD is derived from VDD_IRLED
using resistor R1.
In either power supply configuration, a 1µF decoupling capacitor
should be installed close to the VDD pin, and another 1µF
decoupling capacitor should be placed close to the IR LED anode.
FIGURE 11. TYPICAL APPLICATIONS CIRCUIT
C1, C2: 1µF CERAMIC 10V CAPACITOR
5
6
7
8
4
3
2
1
VDD
SCL
GND
LED+
SDA
INT
IRDR
LED-
INT
SDA
SCL
SMBus MASTER
VDD_IRLED
VDD
VDD_PULLUP
U1
R1
100Ω
R1: 100Ω 5% RESISTOR
C2
1µF
C1
1µF
ISL29147
13 FN8409.3
January 6, 2015
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Soldering Considerations
Convection heating is recommended for reflow soldering;
direct-infrared heating is not recommended. The plastic optical
co-package does not require a custom reflow soldering profile. A
standard reflow soldering profile with a +260°C maximum is
recommended. Additional information regarding soldering the
ISL29147 is included in Intersil Technical Brief TB493.
PCB Layout Considerations
The ISL29147 is relatively insensitive to PCB layout. Adherence to
the following guidelines will ensure first pass success and best
performance.
Route the I2C/SMBus SCL, SDA and the INT traces away from
sources of switching noise.
The ISL29147 pin GND should connect to a low impedance
ground with low resistance and low inductance traces. Ferrite
beads and inductors should be avoided in the ground path. If
necessary, due to RF consideration, the effects of DCR
(DC resistance) should be evaluated on ALS and Proximity
system performance.
A 1µF ceramic decoupling capacitor should be placed as close to
VDD pin as possible.
The ISL29147 drives the IR LED with 0.09ms current pulses. To
supply this pulsed current, a 1 to 10µF bulk decoupling capacitor
(C1) must be connected from the IR LED anode to the GND pin to
minimize instantaneous resistive voltage drop. The connection
from IR LED cathode to the IRDR pin should be short and with
minimal inductance. Similarly, connection from IR LED anode to
VDD_IRLED must be made with a low impedance trace.
For most applications, a single power supply may be used to
power the IR LED and the ISL29147. Use of resistor R1 and
capacitor C2 (Figure 11) to help filter out the power supply noise
generated from IR LED switching, is recommended for best
ISL29147 performance when using a single power supply. For
dual supply operation, resistor R1 should not be installed.
ISL29147
14
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FN8409.3
January 6, 2015
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Revision History
The revision history provided is for informational purposes only and is believed to be accurate, but not warranted. Please go to web to make sure you
have the latest revision.
DATE REVISION CHANGE
January 06, 2015 FN8409.3 Ordering information table on page 2: Corrected typo from ISL29147IR0MZ-T7 to ISL29147IROMZ-T7 (changed
from zero to letter "O")
January 14, 2014 FN8409.2 Updated POD L8.2.40x4 - from rev 4 to rev 5 - changes from rev 4: top view re-drawn - changed from round to oval
detector and added dimensions.
December 9, 2013 FN8409.1 Updated POD L8.2.40x4 - Bottom View changed Pin 1 Index Mark from Pin 1 index mark to Pin 4 index area.
Updated Note 4 to show correct Pin number.
September 16, 2013 FN8409.0 Initial Release.
ISL29147
15 FN8409.3
January 6, 2015
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Package Outline Drawing
L8.2.40x4
8 LEAD OPTICAL CO-PACKAGE
Rev 5, 12/13
BOTTOM VIEW
TYPICAL RECOMMENDED LAND PATTERN
TOP VIEW
Unless otherwise specified, tolerance: Decimal ± 0.05
Pin #4 identifier is a laser-etched dot on bottom surface.
Dimensions in ( ) for Reference Only.
Dimensioning and tolerancing conform to ASME Y14.5m-1994.
3.
2.
Dimensions are in millimeters.1.
NOTES:
4.
1.08±0.05
R0.71±0.05
4.00±0.10
2.40
2.40±0.10
0.20
0.20
1.20±0.10
0.30
2.20
0.90
0.97
0.50
0.65 PIN 4 INDEX AREA
0.80
0.55
0.97
0.80
2.40
PACKAGE OUTLINE
1-LEDC
2-IRDR
3-INT
4-SDA
8-LEDA
7-GND
6-SCL
5-VDD
1.43±0.05
1.65±0.05
0.625
Mouser Electronics
Authorized Distributor
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ISL29147IROMZ-T7