SP4490 Datasheet, PDF (7/12 Pages) Sipex Corporation – Two Panel Electroluminscent Lamp Driver

higher C values can increase lamp brightness.
INT
This is best determined by experimentation. A
rule of thumb is larger coils (1mH) are paired
with a smaller C (680pF) and smaller coils
INT
(470µH) 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.
Rev. 9/12/00
SP4490 Two Panel Electroluminescent Lamp Driver
7
© Copyright 2000 Sipex Corporation