SP4490 Datasheet, PDF (4/12 Pages) Sipex Corporation – Two Panel Electroluminscent Lamp Driver

VDD
2
ROSC
3 ^OSC
4
ON/OFF
EL1/EL2
VDD
IN ⁰
1
1
SEL
SP4490
FF7
5
VSS
6
COIL
7
CAP
fCOIL
fLAMP1
SCR1
fLAMPCOM
fLAMP2
10
EL1
SCR2
8
ELcommon
SCR3
7
EL2
Figure 1: Internal Block Diagram of SP4490
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 V_SS.
The SP4490 contains a DC-AC inverter that can
produce an AC output of 180V (typical) from
PP
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.
Rev. 9/12/00
SP4490 Two Panel Electroluminescent Lamp Driver
4
© Copyright 2000 Sipex Corporation