MP3204 – 6V, 1.3MHz WHITE LED DRIVER

MP3204 Rev. 1.3

www.MonolithicPower.com

4

9/23/2005

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© 2005 MPS. All Rights Reserved.

TM

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.

PWM

COMPARATOR

AMPLIFIER

CONTROL

LOGIC

CURRENT

SENSE

AMPLIFIER

SW

M1

GND

-

+

FB

1.3MHz

OSC

-

+

+

-

+

104mV

MP3204_F01_BD01

2

1

3

Figure 1—Functional Block Diagram