SP4491 datasheet(5/13 Pages) SIPEX

5 / 13 page

Rev. 12/19/00

SP4491 Two Panel Electroluminescent Lamp Driver

DESCRIPTION

The SP4491 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 or stimultaneously. The SP4491

reduces system cost, component count and board

space requirements over a discrete 2 EL driver

approach. The EL lamps operate in opposite

phase so the SP4491 can be easily implemented

in applications driving multi-color or multi-seg-

ment EL lamps. The SP4491 operates from a

+2.2V to +6.0V battery source.

The device

features a low power standby mode that draws

less than 1

µA. 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 SP4491 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 SP4491 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 2: Typical Application Circuit of SP4491

ROSC

VSS

COIL

CAP

SP4491

VBATT

0.1

µF

ROSC

464k

Ω

470

µH

ELEN1

1N4148

CINT

1800pF

VDD

ELcommon

EL1

EL Lamp

C2*

1nF

ELEN2

* optional device

EL2

EL Lamp

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