MP28251 – 20V, 4A SYNCHRONOUS STEP-DOWN CONVERTER

MP28251 Rev. 1.16

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4

4/17/2013

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PIN FUNCTIONS

QFN 2×3mm

Pin #

Name Description

1, 12,

13, 14

GND

Ground. Connect these pins with larger copper areas to the negative terminals of the

input and output capacitors.

2, 11

SW

Switch Output. Use wide PCB traces to make the connection.

3, 15

IN

Supply Voltage. The MP28251 operates from a 4.75V-to-20V input rail. Requires C1 to

decouple the input rail. Use wide PCB traces and multiple vias to make the connection.

4

EN

Enable. EN=1 to enable the MP28251. The EN pin sources 2.3μA. Place a capacitor

from EN to GND for delayed start-up.

5

LPM

Low-Power Mode Input. An active-high signal enables low-power mode operation.

Connect LPM pin to GND to disable it and make the converter always operate in COM.

6

FB

Feedback. Connect to the tap of an external resistor divider from the output to GND to

set the output voltage.

7

SS

Soft Start. Connect an external capacitor to program the soft-start time for the switch-

mode regulator.

8

FREQ/

SYNC

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

switching frequency. This pin also serves as a frequency-synchronous clock input.

9

VCC

Bias Supply. Decouple with 0.1µF capacitor. Decouple capacitor must be close enough

to VCC pin to increase noise immunity.

10

BST

Bootstrap. Requires a capacitor connected between SW and BST pins to form a

floating supply across the high-side switch driver.