Microsemi

Analog Mixed Signal Group

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

Page 5

Copyright

© 2007

Rev. 1.1, 2010-02-26

P

"

LXMG1617A-03-2x

3.3V 2.2W CCFL Programmable Inverter Module

TM

®

TYPICAL APPLICA T ION

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 PWM logic level

signal (figure 1A) may be used up to 5V; however the inverter

will reach maximum current at less than 100% duty cycle.

This can be calculated as approximately 2V divided by the

logic high voltage level; with 3.3V logic level this corresponds

to about 60% duty cycle for maximum lamp current.

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

TTL logic signal to the

SLEEP input.

to the low voltage wire (wire with thinner insulation). Never

regulation.

If both lamp wires have heavy high voltage

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 manufacture’s

allow the user the flexibility to 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

restart the inverter it is necessary to toggle the sleep input or