SP4490EU datasheet(4/12 Pages) SIPEX

4 / 12 page

Rev. 9/12/00

SP4490 Two Panel Electroluminescent Lamp Driver

COIL

SP4490

fCOIL

fLAMP1

fLAMPCOM

SCR1

SCR2

EL1

VSS

VDD

SCR3

EL2

ELcommon

FF7

OSC

fLAMP2

ROSC

CAP

EL1/EL2

ON/OFF

VDD

SEL

IN 0

DESCRIPTION

The SP4490 electroluminescent lamp driver pro-

vides designers of cell phones, PDA's and other

handheld, portable electronic devices with an

integrated solution for driving two EL lamps

independently.

The SP4490 reduces system

cost, component count and board space require-

ments over a discrete 2 EL driver approach. The

EL lamp operates in opposite phase so the SP4490

can be easily implemented in applications driv-

ing multi-color or multi-segment EL lamps. The

SP4490 operates from a +2.2V to +6.0V battery

source. The device features a low power standby

mode that draws less than 1mA. The frequency

of the internal oscillator is set using a single

external resistor. A single external inductor is

required to generate the high voltage AC outputs

to drive the EL lamps. All input pins are ESD

protected with internal diodes to V

DD and VSS.

The SP4490 contains a DC-AC inverter that can

produce an AC output of 180V

PP (typical) from

a 3.0V input voltage. An internal block diagram

of the SP4490 can be found in Figure 1.

Electroluminescent Technology

An EL lamp consists of a thin layer of phospho-

rous material sandwiched between two strips of

plastic which emits light (flouresces) when a

high voltage AC signal is applied across it. It

behaves primarily as a capacitive load. Long

periods of DC voltage applied to the material

tend to reduce its lifetime. With these conditions

in mind, the ideal signal to drive an EL lamp is a

high voltage sine wave. Traditional approaches

to achieve this type of waveform include discrete

circuits incorporating a transformer, transistors

and several resistors and capacitors.

This approach is large and bulky and cannot be

implemented in most handheld equipment. Sipex

offers low power single chip driver circuits spe-

cifically designed to drive small to medium sized

electroluminescent panels. Sipex EL drivers

provide a differential AC voltage without a DC

offset to maximize EL lamp lifetime. The only

additional components required for the EL driver

circuitry are an inductor, resistor and capacitor.

Figure 1: Internal Block Diagram of SP4490

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