SC1155

PROGRAMMABLE SYNCHRONOUS

DC/DC HYSTERETIC CONTROLLER

WITH VRM 9.0 VID RANGE

© 2000 SEMTECH CORP.

PRELIMINARY - August 7, 2000

1

Pentium is a registered trademark of Intel Corporation

TEL:805-498-2111 FAX:805-498-3804 WEB:http://www.semtech.com

DEVICE

(1)

PACKAGE

TEMP. RANGE (T

SC1155CSW.TR

SO-28

0 - 125°C

SC1155EVB

Evaluation Board

ORDERING INFORMATION

Note:

(1) Only available in tape and reel packaging. A reel

contains 1000 devices.

DESCRIPTION

The SC1155 is a synchronous-buck switch-mode con-

troller designed for use in single ended power supply

applications where efficiency is the primary concern.

The controller is a hysteretic type, with a user se-

lectable hysteresis. The SC1155 is ideal for implement-

ing DC/DC converters needed to power advanced mi-

croprocessors such as Pentium

single and multiple processor configurations. Inhibit,

under-voltage lockout and soft-start functions are in-

cluded for controlled power-up.

SC1155 features include an integrated 5 bit D/A con-

verter, temperature compensated voltage reference,

current limit comparator, over-current protection, and

an adaptive deadtime circuit to prevent shoot-through

of the power MOSFET during switching transitions.

Power good signaling, logic compatible shutdown, and

over-voltage protection are also provided. The inte-

grated D/A converter provides programmability of out-

put voltage from 1.1V to 1.85V in 25mV increments.

The SC1155 high side driver can be configured as

either a grounded reference or as a floating bootstrap

driver. The high and low side MOSFET drivers have a

peak current rating of 2 amps.

FEATURES

APPLICATIONS

Athlon is a registered trademark of AMD Corporation

TYPICAL APPLICATION CIRCUIT

IOUT

1

DROOP

2

OCP

3

VHYST

4

VREFB

5

VSENSE

6

AGND

7

SOFTST

8

N/C

9

LODRV

10

LOHIB

11

DRVGND

12

LOWDR

13

DRV

14

VIN12V

15

BOOT

16

HIGHDR

17

BOOTLO

18

HISENSE

19

LOSENSE

20

IOUTLO

21

INHIBIT

22

VID4

23

VID3

24

VID2

25

VID1

26

VID0

27

PWRGD

28

U1

SC1155CSW

R11

2.2

R12

3.9

L2

1.5uH

C7

0.1

R3

2.7k

R1

2k

R4

1k

R2

1k

R5

100

R6

20k

C5

0.001

R7

150

R8

10k

+5V

C8

2.2uF

C9

2.2uF

+12V

R10

10k

R9

10k

C4

0.01

C6

0.1

C17-C19

150uF/16V

L1

1uH

C16

0.1

C27

0.1

PWRGD

INHIB

Vin +5 to +12V

Vout = 1.1 to 1.85V

C2

0.01

C3

0.01

C13

0.33

Q1

IRL3103S

Q2

IRL2203S

C8

0.01

+5V

Vout

GND

C21-C26

150uF/4V

C12

0.33

C20

0.1

Vin

GND