User Manual

BH1750FVI
Technical Note
5/17
www.rohm.com
2009.04- Rev.B
© 2009 ROHM Co., Ltd. All rights reserved.
●Instruction Set Architecture
Instruction Opecode Comments
Power Down 0000_0000
No active state.
Power On 0000_0001
Waiting for measurement command.
Reset 0000_0111
Reset Data register value. Reset command is not acceptable in
Power Down mode.
Continuously H-Resolution Mode 0001_0000
Start measurement at 1lx resolution.
Measurement Time is typically 120ms.
Continuously H-Resolution Mode2 0001_0001
Start measurement at 0.5lx resolution.
Measurement Time is typically 120ms.
Continuously L-Resolution Mode 0001_0011
Start measurement at 4lx resolution.
Measurement Time is typically 16ms.
One Time H-Resolution Mode 0010_0000
Start measurement at 1lx resolution.
Measurement Time is typically 120ms.
It is automatically set to Power Down mode after measurement.
One Time H-Resolution Mode2 0010_0001
Start measurement at 0.5lx resolution.
Measurement Time is typically 120ms.
It is automatically set to Power Down mode after measurement.
One Time L-Resolution Mode 0010_0011
Start measurement at 4lx resolution.
Measurement Time is typically 16ms.
It is automatically set to Power Down mode after measurement.
Change Measurement time
( High bit )
01000_MT[7,6,5]
Change measurement time.
※ Please refer "adjust measurement result for influence of optical window."
Change Masurement time
( Low bit )
011_MT[4,3,2,1,0]
Change measurement time.
※ Please refer "adjust measurement result for influence of optical window."
※ Don't input the other opecode.
●Measurement mode explanation
Measurement Mode Measurement Time. Resolurtion
H-resolution Mode2 Typ. 120ms. 0.5 lx
H-Resolution Mode Typ. 120ms. 1 lx.
L-Resolution Mode Typ. 16ms. 4 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 l x resolution so that it is suitable for darkness ( less than 10 lx )
H-resolution mode2 is also suitable to detect for darkness.
●Explanation of Asynchronous reset and Reset command "0000_0111"
1) Asynchronous reset
All registers are reset. It is necessary on power supply sequence. Please refer "Timing chart for VCC and DVI power
supply sequence" in this page. It is power down mode during DVI = 'L'.
2) Reset command
Reset command is for only reset Illuminance data register. ( reset value is '0' ) It is not necessary even power supply
sequence.It is used for removing previous measurement result. This command is not working in power down mode, so
that please set the power on mode before input this command.