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SC1173

PROGRAMMABLE SYNCHRONOUS DC/DC CONVERTER WITH LOW DROPOUT REGULATOR CONTROLLER

Semtech Corporation 

October 25, 1999

MATERIALS LIST

PROGRAMMABLE SYNCHRONOUS DC/DC

CONVERTER WITH LOW DROPOUT

REGULATOR CONTROLLER

SC1172/3

Qty. Reference Part/Description

4 C1,C5,C13,C 0.1µF Ceramic

18

6 C2,C3,C14- 1500µF/6.3V

C17

3 C11,C12, 330µF/6.3V

C21

1 L1

4µH

3 Q1,Q2,Q3 See notes

Vendor

Various

SANYO

Various

See notes

1 R4

1 R5

1 R6

1 R1

1 R12

1 R13

1 R17

1 U1

5mΩ

IRC

2.32kΩ, 1%, 1/8W Various

1kΩ, 1%, 1/8W

Various

10Ω, 5%, 1/8W

Various

1%, 1/8W

Various

1%, 1/8W

Various

100K, 5% 1/8W Various

SC1172/3CSW

SEMTECH

Notes

MV-GX or equiv. Low ESR

8 Turns 16AWG on MICROMETALS T50-52D core

FET selection requires trade-off between efficiency and

cost. Absolute maximum RDS(ON) = 22 mΩ for Q1,Q2

OAR-1 Series

See Table (Not required for SC1172)

See Table (Not required for SC1172)

SETTING LDO OUTPUT VOLTAGE

VO LDO

3.45V

3.30V

3.10V

2.90V

2.80V

2.50V

1.50V

RB

R12

105Ω

105Ω

102Ω

100Ω

100Ω

100Ω

100Ω

RA

R13

182Ω

169Ω

147Ω

130Ω

121Ω

97.6Ω

18.7Ω

VOUT

=

1.265 ⋅ (RA

RB

+ RB )

+ (IFB

⋅RA )

Where :

IFB = Feedback pin bias current

RA = Top feedback resistor

RB = Bottom feedback resistor

See layout diagram for clarification

RA and RB must be low enough so

that the (IFB ⋅ RA ) term does not cause

significant error

© 1999 SEMTECH CORP.

6

652 MITCHELL ROAD NEWBURY PARK CA 91320

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