MP4350 – 2.5A, 4MHz, 20V STEP-DOWN CONVERTER

MP4350 Rev. 1.0

www.MonolithicPower.com

5

5/26/2008

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OPERATION

The

MP4350

is

a

variable

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

At moderate to high output current, the MP4350

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.

--

+

--

+

1.5ms SS

Gm Error Amp

SS

2.6V

5V

COMP

VIN

BST

SW

GND

FREQ

COMP

FB

EN

SS

0V8

REFERENCE UVLO/

THERMAL

SHUTDOWN

INTERNAL

REGULATORS

OSCILLATOR

--

+

SW

--

+

Level

Shift

CLK

Figure 1—Functional Block Diagram