Microsemi

Analog Mixed Signal Group

11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, 800-877-6458, Fax: 714-893-2570

Page 5

Copyright

© 2007

Rev. 1.0, 2007-11-14

PanelMatch™ "A Series"

LXMG1617A-05-4x

5V 4W CCFL Programmable Inverter Module

TM

®

TY PICAL APPLICATION

LXMG1617A-05-4x

5V

GND

BRITE

SLEEP

0V to

2.0V 500k

DAC or

Pot

CCFL

TUBE

NC

NC

Figure 1

– Brightness Control

(output current set to maximum)

P.W.

10µs to 500µS

BRITE

LXMG1617A-05-4x

0 < P.W. < 100% of period

PWM Signal

from System

Figure 1A

– PWM Brightness Control

LXMG1617A-05-4x

GND

SLEEP

CCFL

TUBE

BRITE

5V

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 500K manual pot. The

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

pot, if desired; add a resistor to set the lower threshold

voltage above the absolute minimum dim level capability.

A 3.3V Logic Level PWM signal from a microcontroller

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 manufacturers. Generally the best

lamp lifetime correlates with driving the CCFL at the

manufacturer’s nominal current setting.

However the

adjust 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 an 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 user’s

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 up to about one

second, after which (without success) the inverter will

shutdown, in this mode the inverter will draw about 8mA

from VIN. In order to restart the inverter it is necessary to