SP4490 datasheet(7/12 Pages) SIPEX

7 / 12 page

Rev. 9/12/00

SP4490 Two Panel Electroluminescent Lamp Driver

higher C

INT values can increase lamp brightness.

This is best determined by experimentation. A

rule of thumb is larger coils (1mH) are paired

with a smaller C

INT (680pF) and smaller coils

(470

µH) are paired with a larger C

INT (1800pF).

Changing the EL lamp Output Voltage

Waveform

Designers can alter the sawtooth output voltage

waveform to the EL lamp. Increasing the capaci-

tance of the integration capacitor, C

INT, will inte-

grate the sawtooth waveform making it appear

more like a square wave.

Printed Circuit Board Layout Sugges-

tions

The EL driver's high-frequency operation makes

PCB layout important for minimizing electrical

noise. Keep the IC's GND pin and the ground

leads of C1 and C

INT less than 0.2in (5mm) apart.

Also keep the connections to the COIL pin as

short as possible. To maximize output power

and efficiency and minimize output ripple volt-

age, use a ground plane and solder the IC's VSS

pin directly to the ground plane.

EL Lamp Driver Design Challenges

There are many variables which can be opti-

mized for specific applications. The amount of

light emitted is a function of the voltage applied

to the lamp, the frequency at which is applied, the

lamp material, the lamp size, and the inductor

used. Sipex supplies characterization charts to

aid the designer in selecting the optimum circuit

configuration.

Sipex will perform customer application evalu-

ations, using the customer's actual EL lamp to

determine the optimum operating conditions for

specific applications. For customers consider-

ing an EL backlighting solution for the first time,

Sipex is able to provide retrofits to non-backlit

products for a thorough electrical and cosmetic

evaluation. Please contact your local Sipex sales

Representative or the Sipex factory directly to

initiate this valuable service.

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