PROGRAMMABLE SYNCHRONOUS DC/DC

CONVERTER WITH LOW DROPOUT

REGULATOR CONTROLLER

SC1172/3

© 1999 SEMTECH CORP.

October 25, 1999

652 MITCHELL ROAD NEWBURY PARK CA 91320

6

MATERIALS LIST

Qty. Reference

Part/Description

Vendor

Notes

4

C1,C5,C13,C

18

0.1µF Ceramic

Various

6

C2,C3,C14-

C17

1500µF/6.3V

SANYO

MV-GX or equiv. Low ESR

3

C11,C12,

C21

330µF/6.3V

Various

1

L1

4µH

8 Turns 16AWG on MICROMETALS T50-52D core

3

Q1,Q2,Q3

See notes

See notes

FET selection requires trade-off between efficiency and

cost. Absolute maximum R

1R4

5m

Ω

IRC

OAR-1 Series

1R5

2.32k

Ω, 1%, 1/8W Various

1R6

1k

Ω, 1%, 1/8W

Various

1R1

10

Ω, 5%, 1/8W

Various

1

R12

1%, 1/8W

Various

See Table (Not required for SC1172)

1

R13

1%, 1/8W

Various

See Table (Not required for SC1172)

1

R17

100K, 5% 1/8W

Various

1

U1

SC1172/3CSW

SEMTECH

SETTING LDO OUTPUT VOLTAGE

R

B

R

A

V

R12

R13

3.45V

105

Ω

182

Ω

3.30V

105

Ω

169

Ω

3.10V

102

Ω

147

Ω

2.90V

100

Ω

130

Ω

2.80V

100

Ω

121

Ω

2.50V

100

Ω

97.6

Ω

1.50V

100

Ω

18.7

Ω

error

t

significan

cause

not

does

term

)

R

I

(

the

that

so

enough

low

be

must

R

and

R

ion

clarificat

for

diagram

layout

See

resistor

feedback

Bottom

R

resistor

feedback

Top

R

current

bias

pin

Feedback

I

:

Where

)

R

I

(

R

)

R

R

(

265

.

1

V

A

FB

B

A

B

A

FB

A

FB

B

B

A

OUT

⋅

=

=

=

⋅

+

+

⋅

=