MP5600 datasheet(13/26 Pages) MPS

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MP5600-COMPACT MULTIPLE-OUTPUT POWER SUPPLY FOR TV-LCD PANEL

MP5600 Rev. 0.9

www.MonolithicPower.com

10/19/2009

MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited.

OPERATION

The MP5600 is a power supply designed for TFT

LCD panels used in TVs and Monitors. It

contains a buck switching regulator to generate

the logic supply rail, a boost switching regulator

to generate the source driver supply, and two

charge-pump regulators to generate the gate

driver

supplies.

Each

regulator

features

adjustable output voltage, internal soft-start, and

timer-delayed fault protection. Figure 1 shows the

total functional block diagram.

Buck Regulator

The buck regulator employs fixed switching

frequency, peak current mode architecture to

obtain the quick response. It uses an internal N-

channel MOSFET to step down the input voltage

to the regulated output voltage. A bootstrap

capacitor connected between SWBK and BST is

required to drive the high-side MOSFET. See the

figure2.

BST

SWBK

IN3

VBK

Regulator

Driver

Current

Sense

OSC

(450/675kHz)

Ramp

Compensation

Ref

SoftStart

FSEL

PWM

Comparator

Protection

FBBK

200mV

0.7 Ref

Delay

DLY3

EN1

GND

Enable Control

Figure 2 —Buck Regulator Block Diagram

At the beginning of a cycle, M1 is off. The EA

output voltage is higher than the current sense

amplifier output, and the current comparator’s

output is low. The rising edge of the oscillator

signal sets the RS Flip-Flop. Its output turns on

M1 thus connecting the SWBK pin and inductor

to the input supply.

The increasing inductor

current is sensed and amplified by the Current

Sense Amplifier. Ramp compensation is summed

to the Current Sense Amplifier output and

compared to the Error Amplifier output by the

PWM Comparator. When the sum of the Current

Sense

Amplifier

output

and

the

Slope

Compensation signal exceeds the EA output

voltage, the RS Flip-Flop is reset and M1 is

turned off. The external schottky rectifier diode

conducts the inductor current. If the sum of the

Current Sense Amplifier output and the Slope

Compensation signal does not exceed the EA

output for a whole cycle, then the falling edge of

the CLK resets the Flip-Flop. The output of the

Error Amplifier integrates the voltage difference

between the feedback and the reference. The

polarity is such that a FBBK pin voltage is lower

than reference increases the EA output voltage.

Since the EA output voltage is proportional to the

peak inductor current, an increase in its voltage

also increases current delivered to the output.

With dual mode feedback feature, the buck

regulator supports both fixed and adjustable

output voltages. Connect FBBT to GND to enable

the 3.3V fixed output voltage. Connect a resistive

voltage-divider between VOBUCK and GND with the

center point connected to FBBT to set the output

voltage.

The buck regulator also includes a 15Ω low side

MOSFET M2, this switch is used to charge the

bootstrap capacitor during startup and reduce the

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