zsp4425 ywyn Corporation, zsp4425 Datasheet - Page 6

• Manufacturer Part Number: zsp4425
• Description: Electroluminescent Lamp Driver For 1.5v Or 2.2v To 4.5v Applications
• Manufacturer: ywyn Corporation

Electroluminescent Technology
What is Electroluminescence?
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 trans-
former, transistors, and several resistors and capacitors.
This approach is large and bulky, and cannot be imple-
mented in most hand held equipment. Zywyn now offers
low power single chip driver circuits specifically designed
to drive small to medium sized electroluminescent panels
if all that is required is one external inductor fast recovery
diode and two capacitors.
Electroluminescent backlighting is ideal when used with
LCD displays, keypads, or other backlit readouts. Its main
Zywyn Corporation
For 1.5V operation, tie HON (pin 8) and V
be driven by the output of a microcontroller capable of sourcing 3mA of current to power on the internal V
enable the HON function of the device.
Contact the factory for additional technical or application support.
Typical Application
Zywyn
NOTE:
Keep coil as close to
ZSP4425 as possible
V
IN
=1.5V
IN4148
V
BATTERY
+
-
0.1μF Low ESR
Decoupling
Capacitor
Figure 2. Typical Application Circuit At 1.5V Operation
C
OSC
C
INT
=180pF
=1800pF
DD
(pin 7) together and connect them to either the system power (V
Single Cell 1.5V Application
C
V
Coil
D1
SS
OSC
ZSP4425
6
use is to illuminate displays in dim to dark conditions for
momentary periods of time. EL lamps typically consume
less than LEDs or bulbs making them ideal for battery
powered products. Also, EL lamps are able to evenly light
an area without creating “hot spots” in the display. The
amount of light emitted is a function of the voltage applied
to the lamp, the frequency at which it is applied, the lamp
material used and its size, and lastly, the inductor used.
Both voltage and frequency are directly related to light
output. In other words, as the voltage or the frequency of
the EL output is increased the light output will also in-
crease. The voltage has a much larger impact on light
output than the frequency does. For example, an output
signal of 168V
15Cd/m
could produce 170V
also yield 15Cd/m
and variations in lamp frequency are to be expected, light
output will also vary from device-to-device however typical
light output variations are usually not visually noticeable.
There are many variables which can be optimized for
specific applications.
HON
EL1
EL2
V
2
DD
, in the same application a different EL driver
PP
with a frequency of 500Hz can yield
2
. Variations in peak-to- peak voltage
PP
NOTE:
Keep high voltage traces
short and away from V
and clock lines
with a frequency of 450Hz and can
Connects to V
or to microcontroller
control output
V
HON=V
HON=0V=OFF
1.5 sq.in.
4nF
EL Lamp
DD
=ON
BATTERY
DD
DD
October 2005
ZSP4425
logic and
BATTERY
rev. 04
), or