BH1751FVI-TR Rohm Semiconductor, BH1751FVI-TR Datasheet - Page 10

• Manufacturer Part Number: BH1751FVI-TR
• Description: IC AMBIENT LIGHT SENSOR 6WSOF
• Manufacturer: Rohm Semiconductor
• Series: -r

Specifications of BH1751FVI-TR

• Wavelength: 560nm
• Output Type: I²C™
• Package / Case: 6-WSOF Exposed Pad
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

●Adjust measurement result for influence of optical window. (sensor sensitivity adjusting )
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BH1751FVI
www.rohm.com
BH1751FVI 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 regisiter). 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.
ex) Procedure for changing target sensor sensitivity to 2 times.
1) Changing High bit of MTreg
2) Changing Low bit of MTreg
3) Input Measurement Command
4) After about 240ms, measurement result is registered to Data Register.
* This example is High Resolution mode, but it accepts the other measurement.
changable range of
MTreg
ST
ST
ST
Please change Mtreg from”0100_0101” (default) to”1000_1010” (default * 2).
( High Resolution mode is typically 120ms, but measurement time is set twice. )
The below table is seeing the changable range of MTreg.
It is possilbe to detect 0.23lx by using this function at H-resolution mode. And it is possilbe to detect 0.11lx by using this
function at H-resolution mode2.
The below formula is to calculate illuminance per 1 count.
The below table is seeing the detail of resolution.
H-reslution mode: Illuminance per 1 count ( lx / count ) = 1 / 1.2 *( 69 / X )
H-reslution mode2: Illuminance per 1 count ( lx / count ) = 1 / 1.2 *( 69 / X ) / 2
MTreg value
0100_0101
0001_1111
1111_1110
Slave Address
Slave Address
Slave Address
decimal
binary
( sensitivity : default * 0.45 )
( sensitivity : default * 0.45 )
at H-resolution mode
0001_1111
Min.
R/W
R/W
R/W
31
lx / count
0
0
0
1.85
0.83
0.23
1.2 : Measurement accuracy
69 : Default value of MTreg ( dec )
X : MTreg value
Ack
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10/16
0100_0101
default
default
Typ.
01000_100
0001_0000
011_01010
69
at H-resolution mode2
lx / count
0.93
0.42
0.11
( sensitivity : default * 3.68 )
( sensitivity : default * 3.68 )
Technical Note
2010.02 - Rev.A
1111_1110
Max.
254
Ack
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Ack
SP
SP
SP