SP4403EU datasheet(6/14 Pages) SIPEX

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SP4403DS/05

SP4403 Electroluminescent Lamp Driver

The Switched H-Bridge Network

The H-bridge consists of two SCR structures

that act as high voltage switches. These two

switches control the polarity of how the lamp is

charged. The SCR switches are controlled by

the f

LAMP signal which is the oscillator frequency

divided by 128. For a 50kHz oscillator, the 7 flip

flops will drive f

LAMP= 390Hz.

When the energy from the coil is released, a high

voltage spike is created triggering the SCR

switches. The direction of current flow is

determined by which SCR is enabled. One full

cycle of the H-bridge will create 128 voltage

steps from ground to 80V (typical) on EL1 and

EL2 (pins 4 and 5, respectively) which are 180

degrees out of phase from each other (see

Figure 5). A differential representation of the

output is shown in Figure 6.

Fine Tuning Performance

Circuit performance of the SP4403 can be

improved with some of the following

suggestions:

Increase EL Lamp Light Output: By

connecting a fast recovery diode from COIL

(pin 3) to C

INT (pin 7), the internal diode of the

switched H-bridge network is bypassed resulting

in an increase in light output at the EL lamp.

We suggest a fast recovery diode, such as the

industry standard 1N4148, be used for D1. This

circuit connection can be found in Figure 2.

Square Wave Output Waveform to the EL

Lamp: A 470pF capacitor at C

INT (pin13) will

act as an integrating capacitor, filtering out any

coil switching spikes or ripple in the output

waveform to the EL lamp (shown if Figure 1).

A designer may change the output waveform to

a square wave by using a 0.1

µFcapacitor(shown

in Figure 2) at C

INT (pin 13).

Printed Circuit Board Layout Suggestions:

The SP4403's high-frequency operation makes

PC layout important for minimizing ground

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

the ground leads of C1 and C

INT in Figure 2 less

than 0.2in (5mm) apart. Also keep the

connections to L1 (pin 3) as short as possible.

To maximize output power and efficiency and

minimize output ripple voltage, use a ground

plane and solder the IC's V

SS (pin 2) directly to

the ground plane.

EL Lamp Driver Design Challenges

There are many variables which can be optimized

for specific applications. The amount of light

emitted is a function of the voltage applied to the

lamp, the frequency at which it 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 (see Figures 7 to 14).

Sipex will perform customer application

evaluations, using the customer's actual EL

lamp to determine the optimum operating

conditions for specific applications. For

customers considering an EL backlighting

solution for the first time, Sipex is able to offer

retrofitted solutions to the customer's existing

LED or non-backlit product for a thorough

electrical and cosmetic evaluation. Please

contact your local Sales Representative for Sipex

or the Sipex factory directly to initiate this

valued service.

SP4403EU Datasheet(PDF) 6 Page - Sipex Corporation

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