© 1997 SEMTECH CORP.

652 MITCHELL ROAD NEWBURY PARK CA 91320

HIGH-VOLTAGE INVERTING

DC-DC CONVERTER

SC1650

January 29, 1998

TYPICAL APPLICATION INFORMATION

The typical application circuit generates an adjustable negative voltage

for contrast bias of LCD displays. Efficiency and output power can be

optimized by using the appropriate inductor and switch. The following

formulas provide a guideline for determing the optimal component val-

()

()

.

Ohm

in

R

,

H

in

L

,

Ampere

in

I

,

Volt

in

V

,

Volt

in

V

:

units

where

,

8

.

0

V

L

3

R

10

and

V

I

200

I

at

V

4

.

0

V

V

I

200

I

V

V

V

:

PNP

V

I

V

V

15

.

0

1

.

11

L

B

OUT

OUT

B

OUT

C

)

SAT

(

CE

OUT

)

MAX

(

C

OUT

CEO

OUT

OUT

µ

−

×

×

≅

=

β

×

=

<

×

≥

+

>

×

×

×

−

=

+

+

+

+

+

+

+