Microsemi

Integrated Products Division

11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570

Page 4

Copyright

© 2000

Rev. 1.0b, 2005-03-03

LX1742

High Efficiency High Voltage Boost Controller

I N T E GRA T ED

PR ODUC T S

A PPL I C ATIO N CIR C U I T S

Typical LCD Bias Applications

V

LX1742

⎟⎟

⎠

⎞

⎜⎜

⎝

⎛

+

=

2

1

REF

OUT

R

R

1

V

V

R

1

R

2

C

1

10µF

C

2

*

1nF

R

CS

4kΩ

L

1

* Optional Component

used to reduce output

voltage ripple.

47µH

CR1

UPS5819

LX1742

GND

FB

CS

SW

SHDN

IN

ADJ

OUT

Figure 1

– Circuit Showing Fixed Output Voltage Operation Using an External Schottky Diode Switch (CR1).

V

LX1742

⎟⎟

⎠

⎞

⎜⎜

⎝

⎛

+

=

2

1

ADJ

OUT

R

R

1

V

V

R

1

R

2

C

1

10µF

C

2

*

1nF

R

CS

4kΩ

L

1

* Optional Component

used to reduce output

voltage ripple.

47µH

R

PWM

100kHz

V

625kΩ

CR1

UPS5819

LX1742

GND

FB

CS

SW

SHDN

IN

ADJ

OUT

Figure 2

– Circuit Showing Dynamic Output Voltage Operation Via PWM Input Using an External Schottky Diode

Switch (CR1).

Note: An in-series RPWM will attenuate the PWM amplitude to the proper signal level at the ADJ pin. With the RPWM value shown, a

PWM signal having a duty of 30% to 50% will generate 0.9V to 1.5V at the ADJ pin.