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PDF SP4405 Data sheet ( Hoja de datos )
| Número de pieza | SP4405 | |
| Descripción | Low Voltage Electroluminescent Lamp Driver with Regulated Output Voltage | |
| Fabricantes | Sipex | |
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Hay una vista previa y un enlace de descarga de SP4405 (archivo pdf) en la parte inferior de esta página. Total 20 Páginas | ||
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® SP4405
Low Voltage Electroluminescent Lamp Driver
with Regulated Output Voltage
s +2.2V to +4.5V Battery Operation
s DC-to-AC Converter Produces
160VPP typical for EL Display Panels
s Single Resistor Controlled Internal
Oscillator
s Low Current Standby Mode
s Internal Feedback Loop Maintains
a Constant Regulated EL Lamp
Voltage Output
APPLICATIONS
s Pagers
s Cellular Phones
s PDAs
DESCRIPTION
The SP4405 is a high voltage output DC-AC inverter specifically designed to drive
electroluminescent lamps to backlight liquid crystal displays, keypads, and backlit readouts
used in battery operated portable equipment. The SP4405 will operate from a +2.2V to +4.5V
battery source. The device features an internal feedback loop that regulates the lamp voltage
output to 160VPP (typical) with varying supply voltages to maintain constant EL lamp brightness
over the life of the battery. The device also has a low power shutdown mode which draws less
than 50nA (typical), ideal for low power portable products. One external inductor is required
to generate the high voltage AC output. One external resistor is used to set the internal
oscillator frequency. The SP4405 is ideal for portable applications such as pagers, cellular
phones, PDAs, and other portable applications using LCDs in dim or low light environments.
The SP4405 is offered in 8-pin SOIC and 8-pin µSOIC packages.
VBATTERY
ELEN 1
VSS 2
COIL 3
EL1 4
SP4405DS/18
SP4405
8 ROSC
7 CINT
6 VDD
5 EL2
ELEN
1
ROSC
450kΩ
VDD 6
ROSC 8
SP4405
3 COIL
7 CINT
C1
0.1µF
C2
1nF
2
VSS
45
EL1 EL2
L1
470µH
*D1
1N4148
CINT
0.1µF
EL Lamp
*optional device
SP4405 Low Voltage Electroluminescent Lamp Driver
1
© Copyright 2000 Sipex Corporation
1 page  
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 SP4405 is a DC-AC inverter made up of:
1. The Oscillator/Frequency Divider, 2. The
Coil, and 3. The Switched H-bridge Network.
Further details of each element follow.
The Oscillator/Frequency Divider
The oscillator provides the SP4405 with an
on-chip clock used to control the coil switch
(fCOIL) and the H-bridge network (fLAMP and fLAMP).
Although the oscillator frequency can be varied
to optimize the lamp output, the ratio of fCOIL/
fLAMP will always equal 128.
Figure 1 shows the oscillator output driving the
coil and the output of the oscillator with 7 flip
flops driving the lamp. The suggested oscillator
frequency is 48.6kHz (ROSC = 450kΩ) for fCOIL.
The oscillator output is internally divided down
by 7 flip flops to create a second internal control
signal at 380Hz for fLAMP.
VBATTERY
ELEN
1
ROSC
450kΩ
VDD 6
ROSC 8
SP4405
3 COIL
7 CINT
C1
0.1µF
C2
1nF
2
VSS
45
EL1 EL2
L1
470µH
*D1
1N4148
CINT
0.1µF
EL Lamp
*optional device
Figure 2. Typical Application Circuit for the SP4405, Set
for
a
Square
Wave
Output
with
C
INT
=
0.1µF
The Coil
The supply VBATTERY can range from +2.2V to
+4.5V. VBATTERY should be chosen such that ICOIL
does not exceed the maximum coil current
specification. The majority of the current goes
through the coil and is typically much greater
than I .
DD
The coil is an external component connected
from VBATTERY to pin 3 of the SP4405. Energy is
stored in the coil according to the equation
E =1/2LI 2 where I , to the first approximation,
LP
P
is the product IP = (tON) (VBATTERY - VCE)/L),
where tON is the time it takes for the coil to reach
its peak current, V is the voltage drop across
CE
the internal NPN transistor for f , and L is the
COIL
inductance of the coil. When the NPN transistor
switch is off, the energy is forced through an
internal 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.
The fCOIL signal controls a switch that connects
the end of the coil at pin 3 to ground or to open
circuit. The fCOIL signal is a 90% duty cycle
signal switching at the oscillator frequency,
SP4405DS/18
SP4405 Low Voltage 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.
180
160
140
120
100
80
60
40
20
0
100 200 300 400 500 600 700 800 900 1000
Oscillator Resistor (kΩ)
Figure 11. Output Voltage vs ROSC
180
160
140
120
100
80
60
40
20
0
1.5 2 2.5 3 3.5 4 4.5 5
Lamp Size (sq.in.)
Figure 12. Output Voltage vs Lamp Size (Lamp Capacitance)
SP4405DS/18
SP4405 Low Voltage Electroluminescent Lamp Driver
11
© Copyright 2000 Sipex Corporation
11 Page | ||
| Páginas | Total 20 Páginas | |
| PDF Descargar | [ Datasheet SP4405.PDF ] | |
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