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PDF SP4414 Data sheet ( Hoja de datos )
| Número de pieza | SP4414 | |
| Descripción | Low Cost Electroluminescent Lamp Driver | |
| Fabricantes | Sipex | |
| Logotipo |  |
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® SP4414
Low Cost Electroluminescent Lamp Driver
s Low Power +2.2V to +4.5V Battery
Operation
s Low-Cost EL Driver Ideal for LED
Backlighting Replacement
s DC-to-AC Inverter can Produce Over
160VPP for EL Lamps
s Requires a 32kHz External Clock Signal
s Synchronize EL Driver Operation to
Existing System Clock for Portable
Applications (i.e. Pagers, Cellular
Phones, PDAs, etc.)
s Low Current Standby Mode
DESCRIPTION
The SP4414 is a high voltage output DC-AC inverter specifically designed to drive electrolu-
minescent lamps to backlight liquid crystal displays, keypads, and backlit readouts used in
battery operated portable equipment. The SP4414 will operate from a +2.2V to +4.5 V battery
source. The device features a low power shutdown mode which draws less than 100nA (typical),
ideal for low power portable products. One external inductor is required to generate the high
voltage AC output. An external clock signal is used to drive the internal control signals for the
coil and EL lamp. The SP4414 is ideal for portable applications such as pagers, cellular
phones, PDAs, and other portable applications using LCDs in dim or low light environments.
The SP4414 is offered in 8-pin SOIC and 8-pin µSOIC packages.
VBATTERY
CLK 1
VSS 2
EL2 3
COIL 4
SP4414
8 ELEN
7 VDD
6 EL1
5 CINT
C1
10nF
VDD 7
ELEN
CLK
SP4414
4 COIL
8
1
2
5 CINT
63
VSS EL1 EL2
L1
2.7mH
*D1
1N4148
CINT
100pF
EL Lamp
*optional device
SP4414DS/17
SP4414 Electroluminescent Lamp Driver
1
© Copyright 2000 Sipex Corporation
1 page  
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.
This approach is large and bulky and can be
difficult to implement in some smaller hand
held equipment. Sipex now offers low power
single chip driver circuits specifically
designed to drive small to medium sized
electroluminescent panels.
Market Applications
Electroluminescent backlighting is ideal when
used with LCD displays, keypads, or other
backlit readouts. Its main use is to illuminate
displays in dim to dark conditions for momentary
periods of time. EL lamps typically consume
less power than LEDs or incandescent bulbs
making them ideal for battery powered products.
Also, EL lamps are able to evenly light an area
without creating any undesirable "hot spots" in
the display.
THEORY OF OPERATION
The SP4414 is a DC-AC inverter made up of:
1. The Frequency Divider, 2. The Coil, and
3. The Switched H-bridge Network. Further
details of each element follow.
The Oscillator/Frequency Divider
The external oscillator provides the SP4414
with a clock signal used to control the coil
switch (fCOIL) and the H-bridge network (fLAMP
and fLAMP). The ratio of fCOIL/fLAMP will always
equal 32 for the SP4414.
The external clock frequency is 32kHz. Figure 1
shows the external clock is internally divided
VBATTERY
C1
10nF
VDD 7
ELEN
CLK
SP4414
4 COIL
8
1
2
5 CINT
63
VSS EL1 EL2
L1
2.7mH
*D1
1N4148
CINT
100pF
EL Lamp
*optional device
Figure 2. Typical Application Circuit for the SP4414
down by a flip flop to drive the coil at 8kHz.
This signal is divided down by 5 more flip flops
to drive the lamp at 250Hz.
The Coil
The supply VBATTERY can range from +2.2V to
+4.5V. VBATTERY and the coil should be chosen
such that I does not exceed the maximum
COIL
coil current specification. The majority of the
current goes through the coil and is typically
much greater than IDD.
The coil is an external component connected
from VBATTERY to pin 4 of the SP4414. Energy is
stored in the coil according to the equation
EL=1/2LIP2 where IP, to the first approximation,
is the product IP = (tON) (VBATTERY - VCE)/
L), where tON is the time it takes for the coil to
reach its peak current, VCE is the voltage drop
across the internal NPN transistor for fCOIL, and
L is
the inductance of the coil. When the NPN
transistor switch is off, the energy is forced
through a diode which drives the switched
H-bridge network. This energy recovery is
directly related to the brightness of the EL
lamp output. There are many variations
among coils; magnetic material differences,
winding differences and parasitic capacitances.
For suggested coil suppliers, refer to Page 7.
SP4414DS/17
SP4414 Electroluminescent Lamp Driver
5
© Copyright 2000 Sipex Corporation
5 Page 
The following performance curves are intended to give the designer a relative scale from which to optimize
specific applications. Absolute measurements may vary depending upon the brand of components chosen.
12
10
8
6
4
2
0
1 2 3 4 5 6 7 8 9 10
Frequency (kHz)
Figure 11. Peak Voltage vs. Frequency
L=1mH (34
L=2.7mH (44
L=4.8mH (60
80
70
60
50
L=1mH (34
40 L=2.7mH (44 Ohms)
L=4.8mH (60 Ohms)
30
20
10
0
10 20 30 40 50 60 70 80 90 100
Frequency (kHz)
Figure 12. Supply Current vs. Frequency
SP4414DS/17
SP4414 Electroluminescent Lamp Driver
11
© Copyright 2000 Sipex Corporation
11 Page | ||
| Páginas | Total 14 Páginas | |
| PDF Descargar | [ Datasheet SP4414.PDF ] | |
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