Technical Note

6/12

www.rohm.com

2010.02 - Rev.A

© 2010 ROHM Co., Ltd. All rights reserved.

BD1204GWL

EN

n

0

0

LED Current Setting

12

n

(N? 16)

n-1

EN

1

0

0

LED Current Setting

EN

16pulse

15pulse

14pulse

13pulse

0.125mA

0.25mA

0.5mA

1mA

LED Current

OFF

●

Separate Function Description

(1) LED driver

a) Register access control protocol

LED current is controlled by only EN terminal. It is possible to access the register inside of this chip by using the

protocol below. Accessing the registers with using this protocol operates LED driver ON/OFF and selecting the mode.

Moreover, MAX current can be outputted without Clock input to EN terminal by holding H zone of fixed time after EN

terminal starting.

< When setting current level >

< When starting by MAX setup >

Fig.5 Register access protocol

Fig.6 Slope control example

( Note )

・

In the case of N > 16, BD1204GWL selects the mode of N = 16.

・

LED current is changed by the pulse of EN pin.

Be careful to noise of EN signal.

・

Reset BD1204GWL when the set is unusual. (Keep EN=L over Toff time.)