POWER MANAGEMENT

November 8, 2007



28V 3A Step-Down Switching Regulator

SC4525A

Typical Application Circuit

Features

Wide input range: 8V to 28V

3A Output Current

200kHz to 2MHz Programmable Frequency

Precision V Feedback Voltage

Peak Current-Mode Control

Cycle-by-Cycle Current Limiting

Hiccup Overload Protection with Frequency Foldback

Soft-Start and Enable

Thermal Shutdown

Thermally Enhanced 8-pin SOIC Package

Fully RoHS and WEEE compliant

Applications

XDSL and Cable Modems

Set Top Boxes

Point of Load Applications

CPE Equipment

DSP Power Supplies

LCD and Plasma TVs

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Description

The SC4525A is a constant frequency peak current-mode

step-down switching regulator capable of producing 3A

output current from an input ranging from 8V to 28V. The

switching frequency of the SC4525A is programmable

up to 2MHz, allowing the use of small inductors and

ceramic capacitors for miniaturization, and high input/

output conversion ratio. The SC4525A is suitable for

next generation XDSL modems, high-definition TVs and

various point of load applications.

Peak current-mode PWM control employed in the

SC4525A achieves fast transient response with simple loop

compensation. Cycle-by-cycle current limiting and hiccup

overload protection reduces power dissipation during

output overload. Soft-start function reduces input start-

up current and prevents the output from overshooting

during power-up.

The SC4525A is available in SOIC-8 EDP package.

Figure 1. 1MHz 10V -28V to 5V/3A Step-down Converter

Efficiency of the 1MHz 10V-28V to 5V/3A Step-Down Converter (Front Page)

Efficiency

40

50

60

70

80

90

0.0

0.5

1.0

1.5

2.0

2.5

3.0

Load Current (A)

SC4525A

12

12

SC4525A

GND

IN

SW

BST

L1

5.2mH

C1

0.1mF

SS/EN

COMP

FB

D2

20BQ030

8.25k

R6

33.2k

10nF

C8

10pF

C5

1nF

L1: Coiltronics CD1-5R2

OUT

5V/3A

D1

1N4148

10V – 28V

ROSC

C2: Murata GRM31CR60J106K

C4

4.7mF

C4: Murata GRM32ER71H475K

VIN

C2

10mFX3

C7

R4

18.2k

R5

24.3k

R7

1MHz 10V-28V to 5V/3A Step-Down Converter (Front Page Schematic)