ambient light sensors - mouser electronics · ambient light sensors june 2008 rohm 2 how are...

Ambient Light Sensors


www.rohmelectronics.com / 1.888.775.ROHM

June 2008 1ROHM

BH1600FVCBH1710FVC


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


June 2008 3ROHM

Types of 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


June 2008 5ROHM

Lineup


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


June 2008 7ROHM

BH1600FVC: Mode Settings


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


June 2008 9ROHM

BH1600FVC: Main Characteristics

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

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


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


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)


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%


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”


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.


June 2008 15ROHM

I2C Slave AddressesTwo I2C addresses can be chosen via the ADDR pin

Note: I2C is a trademark of Philips Corp.


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


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


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


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

ambient light sensors - mouser electronics · ambient light sensors june 2008 rohm 2 how are...

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