Microsemi

Integrated Products

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

Page 5

Copyright

© 2005

Rev. 1.0, 2007-01-24

PanelMatch

™ StayLit™

LXMG1626-05-45

5V Dual 6W CCFL Programmable Inverter Module

TM

®

TY PICAL APPLICATION

LXMG1626-05-45

5V

FAULT

`

GND

BRITE

SLEEP

SET

500K

DAC or

Pot

NC

NC

Figure 1

– Brightness Control

(Output current set to maximum)

P.W.

10µs to 200µS

BRITE

LXMG1626-05-45

0< P. W . < 100 % of period

PWM Signal

from System

Figure 1A

– PWM Brightness Control

LXMG1626-05-45

FAULT

GND

SLEEP

BRITE

5V

Lamp(s) Status

FAULT

Inverter Operation

Normal

Operation

Low

Normal full lamp

current

One Lamp

Open

High

Normal @ ½ lamp

current*

Both Lamps

Open

High

Shutdown

One Lamp High

Side Short to

Ground

High

Normal @ ½ lamp

current*

Both Lamps

High Side Short

to Ground

High

Shutdown

Figure 2

– FAULT Output Operation

* Under some conditions the second lamp will also shutdown, this is especially true

if the inverter draws an arc going open or when shorted.

The brightness control may be a voltage output DAC or

other voltage source, a digital pot or 500K manual pot. The

inverter contains an internal 215K pull-up to 3V to bias the

pot.

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

to high voltage wires from the

ground as this will defeat lamp current regulation.

Use the SET input to program the desired maximum output

current. Generally the best lamp lifetime correlates with

driving the CCFL at the manufactures nominal current

setting.

Typically the SET pin is permanently wired to ground or

intentionally left open.

However it can also be actively

driven, using an open collector, or open drain logic signal.

This will allow dynamic adjustment of 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 dimming ratio is a

factor of both the burst duty cycle and the peak output

current, by using this technique the effective dim ratio can

be increased greater than what the burst duty cycle alone

could provide. Conversely, the SET input could be used to

overdrive the lamp current.

Of course, any possible

degradation of lamp life from such practices is the user’s

responsibility since not all lamps are designed to be under

or overdriven.

Input connector (CN1-8) FAULT signal which is normally

low will toggle high to indicate that an output fault

condition has occurred as summarized in the table to the left

figure 2. FAULT will toggle high if one or both lamps are

open or short circuited. If only one lamp opens, or its high

side is shorted to ground then the other lamp should

continue to operate with the FAULT signal going high.

If

both lamps open and/or both lamps are shorted the FAULT

will toggle high if it is not already high and the inverter

output will shutdown. Also if either low side connection of

the lamps is shorted to ground, or the lamps are shorted

high side to low side, FAULT will go high and the inverter

will shutdown. In order to restart the inverter after a fault, it

is necessary to toggle the

input supply. In fault induced shutdown mode the inverter

will draw about 15mA from VIN supply.