BH1721FVC-TR Rohm Semiconductor, BH1721FVC-TR Datasheet - Page 11

• Manufacturer Part Number: BH1721FVC-TR
• Description: Industrial Optical Sensors Ambient Light Sensor Digital 16bit Serial
• Manufacturer: Rohm Semiconductor
• Type: Ambient Light Sensor with Digital Outputr

Specifications of BH1721FVC-TR

• Product: Ambient Light Sensor
• Wavelength: 560nm
• Output Type: I²C™
• Package / Case: SOT-665
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

●Adjust measurement result for influence of optical window. (sensor sensitivity adjusting )
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BH1721FVC
www.rohm.com
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 I
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. (High Resolution mode is typically 120ms, but
The below table is seeing the changeable range of MTreg.
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)
The below table is seeing the detail of resolution.
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 .
changeable
range of MTreg
Please change Mtreg from”01_0010_1100” (default) to”10_0101_1100” (default * 2).
measurement time is set twice. )
ST
ST
ST
00_1000_1100
01_0010_1100
11_1111_1100
MTreg value
binary
decimal
Slave Address
Slave Address
Slave Address
( sensitivity : default * 0.47 )
( sensitivity : default * 0.47 )
00_1000_1100
Min.
140
1.2 : Measurement accuracy
300 : Default value of MTreg ( dec )
X
R/W
R/W
R/W
0
0
0
: MTreg value
lx / count
1.79
0.83
0.25
11/15
Ack
Ack
Ack
* This example is High Resolution mode, but it accepts the other measurement.
01_0010_1100
default
default
Typ.
300
011_1XXXX
010_10010
0001_0000
2
C Bus interface.
( sensitivity : default * 3.40 )
( sensitivity : default * 3.40 )
11_1111_1100
Technical Note
2010.02 - Rev.A
Max.
1020
* X value is ignore.
Ack
Ack
Ack
SP
SP
SP