Oct 24-06 Rev J

SP638 Synchronous Buck Controller

© 2006 Sipex Corporation

Solved by

TM

SP6138

FEATURES

■

5V to 24V Input step down converter

■

Up to 3A output in a small form factor

■

Highly integrated design, minimal components

■

■

Overcurrent circuit protection with auto-restart

■

Power Good Output, ENABLE Input

■

Maximum Controllable Duty Cycle Ratio up to 92%

■

Wide BW amp allows Type II or III compensation

■

Programmable Soft Start

■

Fast Transient Response

■

Available in 6-Pin QFN package

■

External Driver Enable/Disable

■

U.S. Patent #6,922,04

Synchronous Buck Controller

The SP638 is a synchronous step-down switching regulator controller optimized for small

footprint. The part is designed to be especially attractive for single supply step down con-

version from 5V to 24V. The SP638 is designed to drive a pair of external NFETs using a

fixed 2.5 MHz frequency, PWM voltage mode architecture. Protection features include UVLO,

thermal shutdown, output short circuit protection, and overcurrent protection with auto restart.

The device also features a PWRGD output and an enable input. The SP638 is available in

a space saving 6-pin QFN and offers excellent thermal performance.

TYPICAL APPLICATION CIRCUIT

Now Available in Lead Free Packaging

DESCRIPTION

RS3

4.99KΩ

CBST

0.1uF

R1

68.1KΩ, 1%

RZ3

1KΩ

R2

21.5KΩ, 1%

MT/MB, Si7214DN

47 mΩ, 30V

CZ3

47pF

(Co-Packaged FETs)

CP1

6 pF

RZ2

54.9KΩ

CZ2

100pF

CF1

18pF

12V

CSP

6.8nF

VIN

GND

VOUT

GND

SS

VCC

POWERGOOD

CSS

47nF

ISP

ISN

EN

PGND

GND

PWRGD

VFB

COMP

VIN

BST

GH

SWN

UVIN

GL

3.3V

0-2A

DBST

SD101AWS

CVCC

4.7uF

C5

0.1uF

R3 10KΩ

SP6138

C1

4.7uF

NC

CS

0.1uF

RS2

1KΩ

RS1

1KΩ

COOPER, SD25-2R2

2.2uH, 2.8A, 31mΩ

C2

22uF

ENABLE

Note: Die-attach paddle is connected to GND

ISN

SP6138

16 Pin QFN

3mm x 3mm

8

7

6

5

4

3

2

1

GH

GL

PGND

12

11

10

9

16

15

14

13

GND

ISP

SWN