Microsemi

Analog Mixed Signal Group

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

Page 5

Copyright

© 2007

Rev. 1.0, 2007-10-30

P

"

LXMG1617A-03-2x

3.3V 2.2W CCFL Programmable Inverter Module

TM

®

TY PICAL APPLICATION

LXMG1617A-03-2x

3.3V

GND

BRITE

SLEEP

0V to

2.0V

DAC or

Pot

CCFL

TUBE

NC

NC

500k

806

Optional

Resistor

to adjust

minimum

dimming

level

Figure 1

– Brightness Control

(Output current set to maximum)

P.W.

10µs to 500µS

BRITE

LXMG1617A-03-2x

0 < P.W. < 100% of period

PWM Signal

from System

Figure 1A

– PWM Brightness Control

LXMG1617A-03-2x

GND

SLEEP

CCFL

TUBE

BRITE

3.3V

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, it may be necessary to add a small value resistor in

series with the ground side of the POT to set the lower

threshold voltage above the absolute minimum dim level

capability, especially when both SET pins are programmed

low.

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 manufacturers.

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 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