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PDF BH1721FVC Data sheet ( Hoja de datos )
| Número de pieza | BH1721FVC | |
| Descripción | Digital 16bit Serial Output Type Ambient Light Sensor IC | |
| Fabricantes | ROHM Semiconductor | |
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Ambient Light Sensor IC Series
Digital 16bit Serial Output Type
Ambient Light Sensor IC
BH1721FVC
No.11046EBT10
●Descriptions
BH1721FVC is an digital Ambient Light Sensor IC for I2C bus interface. This IC is the most suitable to obtain the ambient
light data for adjusting LCD and Keypad backlight power of Mobile phone. It is possible to detect wide range at High
resolution. ( 1 - 65528 lx ).
●Features
1) I2C bus Interface ( f / s Mode Support, Slave Address : "0100011" )
2) Spectral responsibility is approximately human eye response
3) Illuminance to Digital Converter
4) Wide range and High resolution. (1 – 65528 lx )
5) Low Current by power down function
6) 50Hz / 60Hz Light noise reject-function
7) 1.8V Logic input interface
8) No need any external parts
9) Light source dependency is little. (ex. Incandescent Lamp. Fluorescent Lamp. Halogen Lamp. White LED. Sun Light)
10) Small measurement variation (+/- 15%)
11) Compact surface mount package 1.6 x 1.6 x 0.55 mm
●Applications
Mobile phone, LCD TV, NOTE PC, Portable game machine, Digital camera, Digital video camera, PDA,
LCD display
●Absolute Maximum Ratings
Parameter
Symbol
Ratings
Units
Supply Voltage
Vmax
4.5
V
Operating Temperature
Topr -40～85 ℃
Storage Temperature
Tstg -40～100 ℃
SDA Sink Current
Imax 7 mA
Power Dissipation
Pd
165※
mW
※70mm × 70mm × 1.6mm glass epoxy board. Derating in done at 2.2mW/℃ for operating above Ta=25℃.
●Operating Conditions
Parameter
VCC Voltage
I2C Reference Voltage
Symbol
Vcc
VDVI
Min.
2.4
1.65
Ratings
Typ.
3.0
-
Max.
3.6
VCC
Units
V
V
www.rohm.com
© 2011 ROHM Co., Ltd. All rights reserved.
1/15
2011.11 - Rev.B
1 page  
BH1721FVC
Technical Note
●Instruction Set Architecture
Instruction
Power Down
Opecode
0000_0000
No active state.
Comments
Power On
0000_0001
Waiting for measurement command.
Continuously Auto-Resolution Mode
Continuously H-Resolution Mode
Continuously L-Resolution Mode
Change Measurement time
( High bit )
Change Masurement time
( Low bit )
※ Don't input the other opecode.
0001_0000
0010_0000
0001_0010
0010_0010
0001_0011
0001_0110
0010_0011
0010_0110
010_MT[9,8,7,6,5]
011_MT[4]_XXXX
Switch measurement mode automatically by illuminance.
Start measurement at 1lx resolution.
Measurement Time is typically 120ms.
Start measurement at 8lx resolution.
Measurement Time is typically 16ms.
Change measurement time.
※ Please refer "adjust measurement result for influence of optical window."
Change measurement time.
※ Please refer "adjust measurement result for influence of optical window."
●Measurement mode explanation
Measurement Mode Measurement Time.
H-Resolution Mode
Typ. 120ms
L-Resolution Mode
Typ. 16ms
Measurement Range.
0 - 8191 lx
0 - 65528 lx
Resolution
1 lx
8 lx
We recommend to use H-Resolution Mode.
Measurement time (integration time) of H-Resolution Mode is so long that some kind of noise (including in 50Hz / 60Hz
noise) is rejected. And H-Resolution Mode is 1 lx resolution so that it is suitable for darkness (less than 20 lx)
Auto-Resolution mode selects measurement mode automatically. It is determined after 16ms (typ.) passes from
measurement start. If BH1721FVC judges that current illuminance is more than 4000 lx, then Data is output at L-resolution
mode, else Data is output after 120ms(typ.) from measurement start at H-resolution mode. Please refer below flow chart.
Start
Lux <= 4000
after 16ms.(typ.)
Select mode
Lux > 4000
DATA output at L-resolution mode
Data output at H-resolution mode after
120ms passes from measurement start.
Auto-Resolution mode measurement
www.rohm.com
© 2011 ROHM Co., Ltd. All rights reserved.
5/15
2011.11 - Rev.B
5 Page 
BH1721FVC
Technical Note
●Adjust measurement result for influence of optical window. (sensor sensitivity adjusting )
BH1721FVC is possible to change sensor sensitivity. And it is possible to cancel the optical window influence (difference with
/ without optical window) by using this function. Adjust is done by changing measurement time. For example, when
transmission rate of optical window is 50% (measurement result becomes 0.5 times if optical window is set), influence of
optical window is ignored by changing sensor sensitivity from default to 2 times
Sensor sensitivity is shift by changing the value of MTreg (measurement time register). MTreg value has to set 2 times if
target of sensor sensitivity is 2 times. Measurement time is also set 2 times when MTreg value is changed from default to 2
times. Low 4bit value is fixed”1100”. Please change high 6bit value of this register via to I2C Bus interface.
ex) Procedure for changing target sensor sensitivity to 2 times.
Please change Mtreg from”01_0010_1100” (default) to”10_0101_1100” (default * 2).
1) Changing High bit of Mtreg
ST Slave Address
R/W
0
Ack
010_10010
Ack SP
2) Changing Low bit of Mtreg
ST Slave Address
R/W
0
Ack
011_1XXXX
Ack SP
* X value is ignore.
3) Input Measurement Command.
ST Slave Address
R/W
0
Ack 0001_0000 Ack SP
* This example is High Resolution mode, but it accepts the other measurement.
4) After about 240ms, measurement result is registered to Data Register. (High Resolution mode is typically 120ms, but
measurement time is set twice. )
The below table is seeing the changeable range of MTreg.
Min.
changeable
range of MTreg
binary
decimal
00_1000_1100
( sensitivity : default * 0.47 )
140
( sensitivity : default * 0.47 )
Typ.
01_0010_1100
default
300
default
Max.
11_1111_1100
( sensitivity : default * 3.40 )
1020
( sensitivity : default * 3.40 )
It is possible to detect 0.25lx by using this function at H-resolution mode.
The below formula is to calculate illuminance per 1 count.
Illuminance per 1 count (lx / count) = 1 / 1.2 *(300 / X)
1.2 : Measurement accuracy
300 : Default value of MTreg ( dec )
X : MTreg value
The below table is seeing the detail of resolution.
MTreg value
00_1000_1100
01_0010_1100
11_1111_1100
lx / count
1.79
0.83
0.25
Please input the opecode at PowerDown state to change Mtreg.There is a possibility of malfunctioning when the opecode to
change Mtreg is input while the illuminance measurement is going .
www.rohm.com
© 2011 ROHM Co., Ltd. All rights reserved.
11/15
2011.11 - Rev.B
11 Page | ||
| Páginas | Total 19 Páginas | |
| PDF Descargar | [ Datasheet BH1721FVC.PDF ] | |
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