BH1750FVI

Technical Note

9/17

www.rohm.com

2009.04- Rev.B

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ex 4) LPF using CR is inserted between VCC and DVI.

This method has the possibility that the Reset section of turning on the power supply can not satisfied. cannot be satisfied.

Please design the set considering the characteristic of the power supply enough.

◆

Notes when CR is inserted between VCC and DVI

※

Please note that there is a possibility that reset section ( 1µs ) can not be satisfied because the power supply is turned on when the rise time of VCC is slow

※

When VCC is turned off, the DVI voltage becomes higher than VCC voltage but IC destruction is not occred if recommended constant

( R1 = 1kOhm, C1 = 1µF ) is used.

※

Please note that there is a possibility that Reset section (1µsec) cannot be satisfied if wait time is not enough long after turning off VCC.

(It is necessary to consider DVI voltage level after turning off VCC.)

◆

Example of designing set when CR ( C = 1µF, R = 1kΩ ) is inserted between VCC and DVI with VCC=2.8V

①

The rise time to 0→2.4V of VCC must use the power supply of 100µs or less.

②

Please wait 25ms or more after VCC turn off ( VCC <= 0.05V ), because it is necessary to secure reset section

( 1µs or more ).

R1 : 1kOhm

0.1µF

C1 : 1µF

VCC

ADDR

GND

SCL

DVI

SDA

BH1750FVI

Reset Section : 1us or more

t1

DVI

2.4V

0.4V

0V

*

Please do the application design to secure Reset section 1us or more after the reclosing of the power supply.

Reset Section : 1us or more

Rise time of power supply : 100us or less

0.05V

Time to power supply reclosing : 25ms or more

れ

DVI

2.4V

0.4V

2.8V

0V

t2