SP4480 datasheet(4/13 Pages) SIPEX

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SP4480DS/06

SP4480 Dual Electroluminescent Lamp Driver

DESCRIPTION

The SP4480 Dual Electroluminescent Lamp

Driver is a low-cost, low voltage device ideal for

the replacement of LED backlighting designs in

keypads, handsets, PDAs and other portable

designs. The EL lamp driver outputs operate in

opposite phase so the SP4480 device can be

easily implemented into applications driving

two EL lamps simultaneously or double-sided

EL lamps. Having a dual lamp driver solution

on a single IC makes available precious printed

circuit board real estate for designers additional

circuitry.

The SP4480 contains a DC-AC inverter that can

produce an AC output of 180V

P-P (typical) from

a +2.2V to +6.0V input voltage. An internal

block diagram of SP4480 can be found in Figure

Figure 1: Internal Block Diagram of SP4480

COIL

SP4480

fCOIL

fLAMP1

SCR1

SCR2

EL2

EL1

ELEN1

VSS

VDD

SCR3

SCR4

EL4

EL3

FF7

OSC

fLAMP2

ELEN2

ROSC

1.8k

Ω

CAP

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 condi-

tions 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 trans-

former, transistors and several resistors and

capacitors. This approach is large and bulky and

cannot be implemented in most handheld equip-

ment. Sipex offers low power single chip driver

circuits specifically 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 life-

time. The only additional components required

for the EL driver circuitry are an inductor, resis-

tor and capacitor.

Electroluminescent backlighting is ideal when

used with LCD's keypads or other backlit dis-

plays. EL lamps uniformly light an area without

creating any undesirable "hot spots" in the dis-

play. Also, an EL lamp consumes less power

that LED's or incandescent bulbs in similar

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