MP28259 – 2A, 4.2V-20V INPUT, FAST TRANSIENT SYNCHRONOUS STEP-DOWN CONVERTER

MP28259 Rev. 1.34

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4

4/27/2012

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PIN FUNCTIONS

QFN12

(2x3mm)

Pin #

Name

Description

9

IN

Supply Voltage. The MP28259 operates from a +4.2V to +20V input rail. C1 is

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

connection.

1, 11, 12

GND

System Ground. These pins are the reference ground for the regulated output

voltage, and require special consideration during PCB layout.

2, 10,

Exposed Pad

SW

Switch Output. Connect with wide PCB traces.

3

BST

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

form a floating supply across the high-side switch driver.

4

VCC

Bias Supply. Decouple with a 4.7µF ceramic capacitor as close to this pin as

possible.

5

EN

EN = 1 to enable the MP28259. For automatic start-up, connect EN pin to VIN with a

pull-up resistor.

7

FB

Feedback. Sets the output voltage when connected to the tap of an external resistor

divider, connected between output and GND.

8

FREQ

switching frequency. Decouple with a 1nF capacitor.

6

PG

Power-Good Output, The output of this pin is an open drain that goes high if the

output voltage is higher than 90% of the nominal voltage. There is a delay of (0.5ms

+ 0.5xSS time) delay from FB ≥ 90% to PG goes high.