SIP12501 データシートの表示（PDF） - Vishay Semiconductors

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SIP12501

Boost Converter for Single/Double AA Cell or NiMH Battery for White LED Applications

Vishay Semiconductors 

SiP12501

Vishay Siliconix

Product is End of Life 3/2014

FUNCTIONAL BLOCK DIAGRAM

VOUT

Compensation

FB

-

E/A

+

VIN

Thermal Shutdown

Start-Up

Antiringing SW

+

PWM

-

Driver

GND

LX

XSHD

Reference and Soft-Start

Oscillator

DETAILED OPERATION

SiP12501 is a 600 kHz boost converter IC, packaged in 6 pin

MLP33, for white LED applications. With start-up from low

battery input voltage of 0.65 V, this device features fixed

frequency voltage mode PWM control with internal frequency

compensation. With its low rDS(on) internal power MOSFET,

this device maintains high efficiency over a wide range of

load current.

Low Voltage Start-Up

SiP12501 is designed to start-up at input voltage of typically

0.65 V. In the beginning, VOUT is lower than VIN because of

the voltage drop of the Schottky diode, the device uses VIN

as the power source for the start-up circuit and uses current

limit with fixed off-time to control the increase of the output

voltage. Once VOUT exceeds VIN, the device uses VOUT as

the power source. When VOUT exceeds 1.89 V, the device

switches to soft-start.

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 works in PWM operation with a

fixed frequency of 600 kHz.

Thermal Shutdown Protection

If the temperature of the device is above 160 °C, the device

will turn off the internal power MOSFET and wait until the

temperature drops below 140 °C, then the device goes into

the soft-start process again and finally the system recovers.

During thermal shutdown, the output voltage drops below

1.89 V minus UVLO hysteresis, start-up will be triggered to

keep the output voltage above 1.89 V.

Antiringing Control

The antiringing control circuitry prevents high frequency

ringing of the LX pin as the inductor current goes to zero by

damping the resonant circuit formed by L and CLX

(capacitance on LX pin). When the IC is shutdown, this

antiringing switch is also turned on.

APPLICATION INFORMATION

White LED Brightness Control

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

on XSHD or by a variable dc voltage to control its brightness.

(see Figure 1.) As control voltage VCTRL increases, the

voltage drop on R2 increases and the voltage drop on R1

decreases. Thus, the LED current decreases. The selection

of R2 and R3 will make the current from VCTRL much smaller

than LED current and much larger than the FB pin bias

current.

VIN

10 µF

XSHD

2

VIN

1

XSHD

10 µH

LX 6

SiP12501

5

XSHD

VOUT

3

FB 4

MBR0520

I LED

0.3 V

15 Ω

4.7 µF

R2

1 kΩ

R3

3.9 kΩ

VCTRL

R1

15 Ω

0.3 - VCTRL R2

15 Ω

R3

15 Ω

15 Ω

15 Ω

www.vishay.com

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Document Number: 73192

S09-1455-Rev. B, 03-Aug-09

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