sp4403 Exar Corporation, sp4403 Datasheet - Page 4

• Manufacturer Part Number: sp4403
• Description: Low Voltage Electroluminescent Lamp Driver
• Manufacturer: Exar Corporation

DESCRIPTION
The SP4403 contains a DC-AC inverter that
can produce an AC output of 180V
+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.
SP4403DS/05
Figure 1. Internal Diagram of the SP4403
0.1 F
C1
V
BATT
450k
R
10nF
OSC
C2
R
V
OSC
DD
6
8
OSC
FF7
Q
Q
ELEN
SP4403 Electroluminescent Lamp Driver
1
PP
from a
SP4403
f
f
f
COIL
LAMP
LAMP
4
2
V
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.
SS
SCR1
EL1
4
5
EL2
© Copyright 2000 Sipex Corporation
SCR2
3
7
EL Lamp
COIL
C
*
INT
optional device
1800pF
1N4148
470 H
C
L1
D1
INT
*
*