MP28248 – 3A, 4.2V-20V INPUT, FAST-TRANSIENT SYNCHRONOUS STEP-DOWN CONVERTER IN QFN12 (2X3mm)

MP28248 Rev 1.0

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4

1/5/2012

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PIN FUNCTIONS

QFN12

(2x3mm)

Pin #

Name

Description

1, 11, 12

GND

System Ground. Reference ground for the regulated output voltage. Requires 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 1µF ceramic capacitor as close to the pin as

possible.

5

EN

EN = 1 to enable the MP28248. For automatic start-up, connect EN pin to VIN with a

pull-up resistor.

6

SS

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

switch mode regulator. When the EN pin goes high, an internal current source (14µA)

When the EN pin goes low, an internal current source (4.5μA) discharges the SS

capacitor and the SS voltage smoothly drops.

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 MP28248 operates from a +4.2V to +20V input rail. Requires C1 to

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