MP3204 데이터 시트보기 (PDF) - Monolithic Power Systems

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MP3204

1.3MHz Fixed Frequency 5 White LED Driver with Open LED Protection

Monolithic Power Systems 

TM

MP3204 – 6V, 1.3MHz WHITE LED DRIVER

OPERATION

The MP3204 uses constant frequency, peak

current mode boost regulator architecture to

regulate a series of white LEDs. The operation

of the MP3204 can be understood by referring

to the block diagram of Figure 1. At the start of

each oscillator cycle the FET is turned on

through the control circuitry. To prevent sub-

harmonic oscillations at duty cycles greater

than 50%, a stabilizing ramp is added to the

output of the current sense amplifier and the

result is fed into the positive input of the PWM

comparator. When this voltage equals the

output voltage of the error amplifier, the power

FET is turned off. The voltage at the output of

the error amplifier is an amplified version of the

difference between the 104mV reference

voltage and the feedback voltage. This is the

manner in which the peak current level keeps

the output in regulation. If the feedback voltage

begins to drop, the output of the error amplifier

increases. This results in more current flowing

through the power FET, thus increasing the

power delivered to the output.

FB 3

104mV

+

-

AMPLIFIER

-

+

PWM

COMPARATOR

CONTROL

LOGIC

1 SW

M1

+

1.3MHz

OSC

CURRENT

SENSE

AMPLIFIER

Figure 1—Functional Block Diagram

2 GND

MP3204_F01_BD01

MP3204 Rev. 1.3

www.MonolithicPower.com

4

9/23/2005

MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited.

© 2005 MPS. All Rights Reserved.

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