ambient light sensors - mouser electronics · ambient light sensors june 2008 rohm 2 how are...
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Ambient Light Sensors
Ambient Light Sensors
www.rohmelectronics.com / 1.888.775.ROHM
June 2008 1ROHM
BH1600FVCBH1710FVC
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Ambient Light Sensors
June 2008 2ROHM
How are ambient light sensors used?LCD-equipped portable equipment• Applications: Mobile phones, digital cameras, video, players,PDAs, notebook PCs, portable gaming equipment
• Enables low current consumption control of LCD backlight brightness under all lighting conditions
Display devices• Applications: LCD TVs/displays, PDP TVs, car navigation systems
• Efficiently controls the brightness for easier viewing
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Ambient Light Sensors
June 2008 3ROHM
Types of Ambient Light Sensors
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Ambient Light Sensors
June 2008 4ROHM
Control backlight brightness in mobile phones• Automatically controls display backlight brightness
• Increases/decreases brightness depending on the environment• Dramatically improves visibility & reduces power consumption
• Automatic keypad ON/OFF• Increases battery operating time
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Ambient Light Sensors
June 2008 5ROHM
Lineup
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Ambient Light Sensors
June 2008 6ROHM
BH1600FVC (Analog Current Output Type)Features• Intensity proportional to output current
• 60 µA (typ) @ 100 lx
• Spectrum sensitivity similar to the human eye
• Internal shutdown function enables lower current consumption
• Small package size (WSOF6): 3.0 x 1.6 x 0.7mm
• Operating power supply voltage: 2.4V ~ 3.6V• Compatible with 1.8V logic input interface
• 2-step output gain control• ⇒ Measurement range 0 to 50,000+ lx
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Ambient Light Sensors
June 2008 7ROHM
BH1600FVC: Mode Settings
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Ambient Light Sensors
June 2008 8ROHM
BH1600FVC: Main Characteristics
• Spectrum sensitivity is similar to the human eye
• Gain switching is possible via Pins GC1 and GC2 (ROHM Proprietary Function)• A wide range of luminosities can be detected based on the corresponding current value
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Ambient Light Sensors
June 2008 9ROHM
BH1600FVC: Main Characteristics
• Lower Temp. Dependency: -30 to +85℃ → ±6 %
• Output Max. Voltage: VCC ‐ 0.1 V (typ.)
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Ambient Light Sensors
June 2008 10ROHM
BH1710FVC (Digital Output Type)Features• Intensity proportional to 16 bit digital output
• Compatible with a wide range of intensities:• 0 ~ 65,535 lx
• I2C bus interface (Fast Mode Max. 400kHz)• Supports 1.8V logic I/F
• Spectrum sensitivity similar to the human eye
• Internal shutdown function enables low current consumption
• 50Hz/60Hz noise rejection ensures more stable sensing
• Operating power supply voltage: 2.4V ~ 3.6V
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Ambient Light Sensors
June 2008 11ROHM
BH1710FVC: Characteristics
• ICC current is independent of luminosity
• Compatible with a wide range of intensities: 0 ~ 65,535 lx (1 lx steps)
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Ambient Light Sensors
June 2008 12ROHM
BH1710FVC: Characteristics50Hz/60Hz Noise Rejection Data
• Fluorescent light fluctuates ±25%, synchronized with the AC supply
• BH1710 detects fluctuating light synchronized with the AC supply (50/60Hz) and outputs values stable within ±1%
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Ambient Light Sensors
June 2008 13ROHM
Digital Light Sensor IC Output Format
Ex: High Byte = 1000_0011Low Byte = 1001_0000
Illuminance = (215+29+28+27+24 ) / 1.2 ≒ 28067 [ lx ]
The lower 5 bits of L – Res. mode is “00000”
The lower 2 bits of M – Res. mode is “00”
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Ambient Light Sensors
June 2008 14ROHM
Digital Light Sensor ICs: Minimum resolution andmeasurement time3 measurement modes:
Optical noise rejection increases with measurement time. In H-Resolution mode optical noise at 50Hz/60Hz can be eliminated.
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Ambient Light Sensors
June 2008 15ROHM
I2C Slave AddressesTwo I2C addresses can be chosen via the ADDR pin
Note: I2C is a trademark of Philips Corp.
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Ambient Light Sensors
June 2008 16ROHM
Relative Spectral Sensitivity of Fluorescent / Incandescent Light
• Emits light in the visible spectral range. Nearly no light emitted in the infrared spectrum.
• The energy from the infrared region is larger than from the visible spectrum
The spectrumdiffers based on the
optical source
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Ambient Light Sensors
June 2008 17ROHM
Relative Spectral Sensitivity of Fluorescent / Incandescent Light
ROHM Competitor Product
• ROHM offers stable output regardless of light source
• Competitor sensors output different values depending on the light source
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Ambient Light Sensors
June 2008 18ROHM
Analog / Digital Light Sensor ICs
BH1600FVC BH1710FVC
• The output current is proportional to the brightness
• The output is converted into voltage by applying external resistance, then connected to the ADC
• The output digital value (16bit) is proportional to the brightness
• The output is connected via I2C bus line
• No external parts required
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Ambient Light Sensors
June 2008 19ROHM
BH1600FVC: Application Example (LED Driver)
Direct backlight brightness control is possible using the BH1600FVC incombination with the BD608xGU Intelligent LED Driver
BH1600FVC