POWER MANAGEMENT

1

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SC1155

Programmable Synchronous DC/DC

Hysteretic Controller with VRM 9.0 VID Range

PRELIMINARY

.eatures

Applications

Revision 2, June 2001

Description

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

troller designed for use in single ended power supply ap-

plications where efficiency is the primary concern. The

controller is a hysteretic type, with a user selectable hys-

teresis. The SC1155 is ideal for implementing DC/DC

converters needed to power advanced microprocessors

tiple processor configurations. Inhibit, under-voltage lock-

out and soft-start functions are included 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 MOS.ET during switching transitions. Power

good signaling, logic compatible shutdown, and over-volt-

age protection are also provided. The integrated D/A

converter provides programmability of output voltage

from 1.1V to 1.85V in 25mV increments.

The SC1155 high side driver can be configured as either

a ground-referenced or as a floating bootstrap driver.

The high and low side MOS.ET drivers have a peak cur-

rent rating of 2 amps.

Typical Application Circuit

R12

1.0

R14

1.6

L2

1.0uH

R3

*

R1

*

R4

1k

R2

1k

R5

*

R6

20k

R7

*

R8

10k

C5

C10

+12V

C8

0.033

R10

1k

+5V

R9

10k

+5V

C7

0.1

C1

0.1

Cin

Bulk

L1

0.5uH

PWRGD

INHIB

"POWER GOOD"

"INHIBIT"

+

_

Vin +5V/12V

1.10 to 1.825V

+

_

C9

1.0

Q1

.DB6035AL

Q2

.DB7030BL

Cout

Bulk

C4

0.01

R11

1k

C6

0.1

Cin

H.

Cout

H.

C2

0.001

C3

0.1

*) for the values see specific application circuit somewhere else in the datasheet

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

SC1155