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Document Number: 73193

S-71822-Rev. C, 03-Sep-07

Vishay Siliconix

SiP12401

FUNCTIONAL BLOCK DIAGRAM

DETAILED OPERATION

SiP12401 is a 600 kHz boost controller IC, packaged in 6-pin

MLP33, for white LED applications. It features fixed

frequency voltage mode PWM control with internal frequency

this device maintains high efficiency over a wide range of

load current.

Soft-Start

During soft-start, the loop compensation guarantees the slow

increase of the output voltage and inrush current, so that no

large voltage overshoot and inrush current occur when the

soft-start is ended.

PWM operation

After soft-start, the device is working in PWM operation with

a fixed frequency of 600 kHz.

APPLICATION INFORMATION

White LED Brightness Control

The current of white LED can be adjusted by PWM signal on

the XSHD pin or by a variable dc voltage to control its

increases, the voltage drop on R2 increases and the voltage

drop on R1 decreases. Thus, the LED current decreases.

much smaller than LED current and much larger than the FB

pin bias current.

Compensation

Reference and Soft-Start

Oscillator

Driver

-

+

PWM

+

-

E/A

AGND

PGND

FB

XSHD

EXT

XSHD

AGND

SiP12401

PGND

EXT

FB

1

3

4

6

2

5

22 µH

XSHD

10 µF

4.7 µF

MBR0520

15

Ω

Si2302ADS

R3

3.9 k

Ω

R2

1 k

Ω

I

LED

0.3 V

15

Ω

0.3

V

CTRL

15

Ω

R2

R3

-