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

MP4350 Rev. 1.0

www.MonolithicPower.com

3

5/26/2008

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© 2008 MPS. All Rights Reserved.

PIN FUNCTIONS

Pin #

Name Description

1, 2

SW

Switch Node. This is the output from the high-side switch. A low forward drop Schottky diode to

ground is required. The diode must be close to the SW pins to reduce switching spikes.

3

EN

Enable Input. Pulling this pin below the specified threshold shuts the chip down. Pulling it up

above the specified threshold or leaving it floating enables the chip.

4

COMP

Compensation. This node is the output of the error amplifier. Control loop frequency

compensation is applied to this pin.

5

FB

Feedback. This is the input to the error amplifier. An external resistive divider connected

6

GND

Ground. It should be connected as close as possible to the output capacitor to shorten the high

current switch paths.

7

FREQ

Switching Frequency Program Input. Connect a resistor from this pin to ground to set the

switching frequency.

8, 9

VIN

Input Supply. This supplies power to all the internal control circuitry, including the bootstrap

regulator and the high-side switch. A decoupling capacitor to ground must be placed close to

this pin to minimize switching spikes.

10

BST

Bootstrap. This is the positive power supply for the internal floating high-side MOSFET driver.

Connect a bypass capacitor between this pin and SW pin.

TYPICAL PERFORMANCE CHARACTERISTICS

Efficiency vs

Load Current

100

90

80

70

60

50

40

0

0.5

1.0

1.5

2.0

2.5

LOAD CURRENT (A)

10V/div.

AC Coupled

10mV/div.

1A/div.

10V/div.

AC Coupled

20mV/div.

1A/div.

Steady State

Steady State

Efficiency vs

Load Current

100

90

80

70

60

50

40

0

0.5

1.0

1.5

2.0

2.5

LOAD CURRENT (A)

Steady State

10V/div.

AC Coupled

10mV/div.

1A/div.

Oscillating Frequency

4000

3500

3000

2500

2000

1500

1000

500

0

10

100

1000