SP4403 Datasheet, PDF (4/14 Pages) Sipex Corporation – Low Voltage Electroluminescent Lamp Driver

DESCRIPTION
The SP4403 contains a DC-AC inverter that
can produce an AC output of 180V_PP from a
+2.2V to +4.5V input voltage. An internal block
diagram of the SP4403 can be found in Figure 1.
The SP4403 is built on Sipex's dielectrically
isolated BiCMOS process that provides the
isolation required to separate the high voltage
AC signal used to drive the EL lamp from the
low voltage logic and signal processing circuitry.
This ensures latch-up free operation in the
interface between the low voltage CMOS
circuitry and the high voltage bipolar circuitry.
The SP4403 is ideal for applications driving
EL lamps to backlight LCD displays, key
panels, and other backlit readouts used in
battery operated portable equipment.
A total of only six external components are
required for the standard operation of the
SP4403: an inductor, a fast recovery diode,
three capacitors and a resistor. A diagram of the
SP4403 in a typical application can be found
in Figure 2.
Electroluminescent Technology
An EL lamp is basically a strip of plastic that is
coated with a phosphorous material which emits
light (fluoresces) when a high voltage (>40V)
which was first applied across it, is removed or
reversed. Long periods of DC voltages applied
to the material tend to breakdown the material
and reduce its lifetime. With these considerations
in mind, the ideal signal to drive an EL lamp is
a high voltage sine wave. Traditional approaches
to achieving this type of waveform included
discrete circuits incorporating a transformer,
transistors, and several resistors and capacitors.
VBATT
VDD ₆
ROSC
450kΩ
ROSC 8 _OSC
C1
0.1µF
C2
10nF
Q
FF7
Q
1
ELEN
Figure 1. Internal Diagram of the SP4403
SP4403
fCOIL
fLAMP
SCR1
3 COIL
L1
470µH
7 CINT
1ND41148^*
SCR2
18C0^I0^NTpF^*
fLAMP
2
VSS
4
5
EL1 EL2
EL Lamp
*optional device
SP4403DS/05
SP4403 Electroluminescent Lamp Driver
4
© Copyright 2000 Sipex Corporation