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Ambient Light Sensors

Ambient Light Sensors

www.rohmelectronics.com / 1.888.775.ROHM

June 2008 1ROHM

BH1600FVCBH1710FVC

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

Ambient Light Sensors

June 2008 3ROHM

Types of Ambient Light Sensors

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

Ambient Light Sensors

June 2008 5ROHM

Lineup

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

Ambient Light Sensors

June 2008 7ROHM

BH1600FVC: Mode Settings

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

Ambient Light Sensors

June 2008 9ROHM

BH1600FVC: Main Characteristics

• Lower Temp. Dependency: -30 to +85℃ → ±6 %

• Output Max. Voltage: VCC ‐ 0.1 V (typ.)

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

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)

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%

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”

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.

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.

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

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

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

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