SP4491 Datasheet, PDF (5/13 Pages) Sipex Corporation – Two Panel Electroluminscent 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 1µA. 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 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.
VBATT
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.
C1
0.1µF
ELEN1
ELEN2
ROSC
464kΩ
C2*
1nF
1
4
VDD
2
SP4491
COIL
6
ROSC
3
10 8
EL1 ELcommon
7
CAP
5
VSS
9
EL2
* optional device
L1
470µH
D1
1N4148
CINT
1800pF
Figure 2: Typical Application Circuit of SP4491
EL Lamp
EL Lamp
Rev. 12/19/00
SP4491 Two Panel Electroluminescent Lamp Driver
5
© Copyright 2000 Sipex Corporation