MP4560 – 2A, 2MHz, 55V STEP-DOWN CONVERTER

MP4560 Rev. 1.0

www.MonolithicPower.com

7

11/5/2012

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BLOCK DIAGRAM

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LOGIC

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0.5ms SS

SS

COMP

ISW

VIN

BST

SW

FREQ

GND

COMP

FB

EN

SS

0V8

REFERENCE

UVLO

INTERNAL

REGULATORS

OSCILLATOR

Figure 1—Functional Block Diagram

OPERATION

The MP4560 is a programmable frequency,

non-synchronous, step-down switching regulator

with an integrated high-side high voltage power

MOSFET. It provides a single highly efficient

solution with current mode control for fast loop

response and easy compensation. It features a

wide input voltage range, internal soft-start

control and precision current limiting. Its very low

operational quiescent current makes it suitable

for battery powered applications.

PWM Control Mode

At moderate to high output current, the MP4560

operates in a fixed frequency, peak current

control mode to regulate the output voltage. A

PWM cycle is initiated by the internal clock. The

power MOSFET is turned on and remains on

until its current reaches the value set by the

COMP voltage. When the power switch is off, it

remains off for at least 100ns before the next

cycle starts. If, in one PWM period, the current in

the power MOSFET does not reach the COMP

set current value, the power MOSFET remains

on, saving a turn-off operation.

Pulse Skipping Mode

Under

light

load

condition

the

switching

frequency stretches down zero to reduce the

switching loss and driving loss.

Error Amplifier

The error amplifier compares the FB pin voltage

with the internal reference (REF) and outputs a

current proportional to the difference between the

two. This output current is then used to charge

the external compensation network to form the

COMP voltage, which is used to control the

power MOSFET current.

During operation, the minimum COMP voltage is

clamped to 0.9V and its maximum is clamped to

2.0V. COMP is internally pulled down to GND in

shutdown mode. COMP should not be pulled up

beyond 2.6V.