MP1423 – 3A, 23V, 385KHz STEP-DOWN CONVERTER

MP1423 Rev. 1.1

www.MonolithicPower.com

3

1/6/2006

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TM

TYPICAL PERFORMANCE CHARACTERISTICS

VEN

5V/div.

VOUT

2V/div.

IL

1A/div.

MP1423-TPC02

Soft-Start

CSS Open, VIN = 10V, VOUT = 3.3V,

1.5A Resistive Load

VEN

5V/div.

VOUT

2V/div.

IL

1A/div.

MP1423-TPC03

VEN

5V/div.

VOUT

2V/div.

IL

1A/div.

1ms/div.

MP1423-TPC04

MP1423-TPC01

100

90

80

70

60

50

0

0.5 1.0 1.5 2.0 2.5 3.0 3.5

LOAD CURRENT (A)

Efficiency Curve

VIN = 7V

VIN=5.0V

VIN=2.5V

VIN=3.3V

PIN FUNCTIONS

Pin #

Name

Description

1

BS

High-Side Gate Drive Bootstrap Input. BS supplies the drive for the high-side N-Channel

MOSFET switch. Connect a 4.7nF or greater capacitor from SW to BS to power the high side

switch.

2

IN

Power Input. IN supplies the power to the IC, as well as the step-down converter switches.

Drive IN with a 6V to 23V power source. Bypass IN to GND with a suitably large capacitor to

eliminate noise on the input to the IC. See Input Capacitor

3

SW

Power Switching Output. SW is the switching node that supplies power to the output. Connect

the output LC filter from SW to the output load. Note that a capacitor is required from SW to BS

to power the high-side switch.

4

GND

Ground. (Note: For the SOIC8N package, connect the exposed pad on backside to Pin 4).

5

FB

Feedback Input. FB senses the output voltage to regulate said voltage. Drive FB with a

resistive voltage divider from the output voltage. The feedback threshold is 1.222V. See

Setting the Output Voltage