MP28258 – 3A, 4.2V-20V INPUT, FAST TRANSIENT SYNCHRONOUS STEP-DOWN CONVERTER IN QFN12 (2X3mm)

MP28258 Rev 1.14

www.MonolithicPower.com

4

9/25/2012

MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited.

© 2012 MPS. All Rights Reserved.

PIN FUNCTIONS

QFN12

(2x3mm)

Pin #

Name

Description

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 using wide PCB traces.

3

BST

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

floating supply across the high-side switch driver.

4

VCC

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

possible.

5

EN

EN = 1 to enable the MP28258. For automatic start-up, connect EN pin to VIN with a

pull-up resistor.

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 0.5ms delay between

when FB ≥ 90% to when the PG pin goes high.

7

FB

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

divider that is connected between output and GND.

8

FREQ

frequency. Decouple with a 1nF capacitor.

9

IN

Supply Voltage. The MP28258 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.