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SM8133B

White LED Driver IC

Nippon Precision Circuits  

SM8133B

Example 3. Set LED1 to LED6 to 30mA drive, temporarily turn OFF, turn ON again,

and reset using RESETB input without group setting

Input “2FH”(A group current setting 30mA) and “58H” (A group ON) from the serial interface. LED1 to

LED6 turn ON after the soft start ends. While the LEDs are ON, input “50H” (A group OFF) to turn the LEDs

OFF and transfer the SM8133B to standby mode. The internal register setting “2FH” (A group current setting

30mA) data is retained during standby mode, so you need to input “58H” (A group ON) only to turn the LEDs

ON again. At this point, the charge pump soft start circuit operates again, taking a soft start time of approxi-

mately 1.3ms from when the data is input to when the LEDs turn ON. If RESETB is connected to the micro-

controller power supply and the supply goes LOW, the SM8133B is reset, the LEDs turn OFF, and operation

transfers to standby mode.

RESETB

LED mode

EN

SCK

SDA

ILED1 to 6

Reset mode

Set A Group current : 30mA (2FH)

12345678

A group ON (58H)

LED ON mode

12 3 45 6 78

A group OFF (50H)

12 3 45678

Soft start time

Approx. 30mA

A group ON (58H)

12 3 45 6 7 8

Reset

Reset mode

Soft start time

Approx. 30mA

Example 3 input waveform

SEIKO NPC CORPORATION —19

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