Microsemi

Integrated Products

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

Page 6

Copyright

© 2002

Rev. 1.0b, 2005-01-17

PanelMatch

™

LXM1623-12-4x

12V Dual 4W CCFL Programmable Inverter Module

I N T E GRA T ED

PR ODUC T S

TY PI CAL APPLI CATI O N

LXM1623-12-4x

12V

SET

2

GND

V

HI

V

LO

BRITE

V

IN1

SLEEP

SET

1

0.45V

to 2.0V

1.8K

20K

DAC or

Pot

CCFL

TUBE

NC

NC

ONE OF

TW O

Figure 1

– Brightness Control

(Output current set to maximum)

P.W .

10us to 125uS

BRITE

LXM1623-12-4x

0 < P.W. < 100% of period

PW M Signal

from System

Figure 1A

– PWM Brightness Control

LXM1623-12-4x

SET

2

GND

V

HI

V

LO

SLEEP

SET

1

CCFL

TUBE

BRITE

12V

V

IN1

ONE OF

TW O

L

L

L

H

H

L

H

H

L=GND; H=Open

Figure 2

– Max Output Current

The brightness control may be a voltage output DAC or

other voltage source, a digital pot or 20K manual pot. The

inverter contains an internal 10K pull-up to 3V to bias the

pot, add a 1.8K resistor to set the lower threshold voltage.

A 3.3V Logic Level PWM signal from a micro-controller

may also be used as shown in Figure 1A.

If you need to turn the inverter ON/OFF remotely, connect

to TTL logic signal to the

lamp current regulation. If both lamp wires have heavy

This wire is typically white.

desired maximum output current. Using these two pins in

combination allows the inverter to match a wide variety of

panels from different manufactures.

Generally the best

lamp lifetime correlates with driving the CCFL at the

current to the maximum allowable output current to

increase panel brightness at the expense of some reduced

lamp life.

Although the SET pins are designed such that just leaving

them open or grounding them is all that is needed to set the

output current, they can also be actively set. Using a open

collector or open drain logic signal will allow you to

reduce the lamp current for situations where greater dim

range is required, as an example in nighttime situations. In

conjunction with a light sensor or other timer the panel

could be set to higher brightness (maximum output

current) for daytime illumination and lower brightness

(minimum or typical output current) at nighttime. Since

the dim ratio is a factor of both the burst duty cycle and the

peak output current, using this technique the effective dim

ratio can be increased greater than the burst duty cycle

alone. Conversely the SET inputs could be used to

overdrive the lamp temporarily to facilitate faster lamp

warm up at initial lamp turn on. Of course any possible

degradation on lamp life from such practices is the users

responsibility since not all lamps are designed to be

overdriven.

The inverter has a built in fault timeout function. If the

output is open (lamp disconnected or broken) or shorted

the inverter will attempt to strike the lamp for several

seconds. After about 2 seconds without success the inverter

will shutdown.

In order to restart the inverter it is

supply