SP4428DS/16
SP4428 Electroluminescent Lamp Driver
Copyright 2000 Sipex Corporation
1
DESCRIPTION
The SP4428 is a high voltage output DC-AC converter that can operate from a single 1.5 VDC
power supply. The SP4428 is capable of supplying 200 V
PP
(typical), making it ideal for driving
electroluminescent lamps. The device features 1
A (typical) standby current, for use in low
power portable products. One external inductor is required to generate the high voltage
charge, and one external capacitor is used to produce a clock signal that generates the coil
and lamp frequencies. The SP4428 is ideal for PDAs, pagers, and other low power portable
applications using LCDs in dim or low light environments. The SP4428 is offered in an 8-pin
narrow SOIC. For delivery in die form, please consult the factory.
s
Low Power +1.1V to +1.7V Single
Cell Operation
s
Low-Cost EL Driver Ideal for Backlighting
s
DC-to-AC Inverter Generates High
Voltage AC to Drive EL Lamps
s
Externally Adjustable Oscillator
s
Low Current Standby Mode
APPLICATIONS
s
Pagers
s
Watches
s
Backlit LCD Displays
SP4428
Electroluminescent Lamp Driver
High Drive Capability for Low Voltage Applications
Block Diagram
HON
V
DD
D1
V
SS
COIL
EL2
EL1
SP4428
8
7
4
3
2
1
5
6
C
OSC
SP4428DS/16
SP4428 Electroluminescent Lamp Driver
Copyright 2000 Sipex Corporation
2
SPECIFICATIONS
(T= 25
C; V
DD
= 1.5V; Lamp Capacitance = 4.7nF; Coil = 470
H at 4.9 Ohms; C
OSC
= 180pF unless otherwise noted) C
INT
= 1800pF
ABSOLUTE MAXIMUM RATINGS
These are stress ratings only and functional operation of the device at
these ratings or any other above those indicated in the operation sections
of the specifications below is not implied. Exposure to absolute maximum
rating conditions for extended periods of time may affect reliability.
TA= +25C unless otherwise noted
V
DD
............................................................................................................5V
Input Voltages/Currents
HON (pin1).........................................-0.5V to (V
DD
+0.5V)
COIL (pin3)............................................................100mA
Lamp Outputs.............................................................................230V
PP
Storage Temperature....................................................-65C to +150C
Power Dissipation Per Package
8-pin NSOIC (derate 6.14mW/
o
C above +70
o
C).................................500mW
R
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.
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=
The information furnished herein by Sipex has been carefully reviewed
for accuracy and reliability. Its application or use, however, is solely the
responsibility of the user. No responsibility for the use of this information
is assumed by Sipex, and this information shall not explicitly or implicitly
become part of the terms and conditions of any subsequent sales
agreement with Sipex. Specifications are subject to change without
prior notice. By the sale or transfer of this information, Sipex assumes
no responsibility for any infringement of patents or other rights of third
parties which may result from its use. No license or other proprietary
rights are granted by implication or otherwise under any patent or
patent rights of Sipex Corporation.
SP4428DS/16
SP4428 Electroluminescent Lamp Driver
Copyright 2000 Sipex Corporation
3
THEORY OF OPERATION
The SP4428 is made up of three basic circuit
elements, an oscillator, coil, driver and switched
H-bridge network. The oscillator provides the
device with an on-chip clock source used to control
the charge and discharge phases for the coil and
lamp. An external capacitor connected between
pins 1 and V
SS
allows the user to vary the oscillator
frequency. For a given choice of coil inductance
there will be an optimum C
OSC
Capacitor value that
gives the maximum light output in a given lamp.
The suggested oscillator frequency is 28.8kHz
(C
OSC
=180pF). The oscillator output is internally
divided to create the control signal f
LAMP
.
The oscillator output is internally divided down
by 6 flip flops, a 28.8kHz signal will be divided
into 6 frequency levels; 14.4kHz, 7.2kHz, 3.6kHz,
1.8kHz, 900Hz, and 450Hz. The oscillator output
(28.8kHz) is used to drive the coil (see figure 2 on
page 7) and the sixth flip flop output (300Hz) is
used to drive the lamp. Although the oscillator
frequency can be varied to optimize the lamp
output, the ratio of f
COIL
/f
LAMP
will always equal 64.
The coil is an external component connected from
V
BATTERY
to pin 3 of the SP4428. Energy is
developed in the coil according to the equation
E
L
=1/2LI
2
where the current I is defined as
I=(V
BATTERY
-IR-V
OL
)/R
T
. In order to maximize the
PIN DESCRIPTION
Pin 1 C
OSC
- Connect CAP from V
SS
to Pin 1 to
set Oscillator frequency.
Pin 2 V
SS
- Power supply common, connect to
ground.
Pin 3 Coil- Coil input, connect coil from
V
BATTERY
to Pin 3.
Pin 4 D1- Diode cathode connection.
Pin 5 EL2- Lamp driver output1, connect to
EL lamp.
Pin 6 EL1- Lamp driver output2, connect to
EL lamp.
Pin 7 V
DD
- Power supply for driver, connect to
system V
DD
.
Pin 8 HON- Enable for driver operation,
high = active; low = inactive.
1
2
3
4
8
7
6
5
SP4428
SP4428 Schematic
Q
Q
HON
SCR1
SCR2
OSC
FF1
FF6
EL Lamp
1M
V
DD
Coil
5
6
EL1
EL2
1
Cap1
2
V
SS
V
BATTERY
V
DD
7
3
470
H/4.9
8
180pF
IN4148
Optional
1,800pF
4
D1
.1
F
C
OSC
f
COIL
f
LAMP
f
LAMP
SP4428DS/16
SP4428 Electroluminescent Lamp Driver
Copyright 2000 Sipex Corporation
4
energy produced by the coil V
BATTERY
should
represent the largest voltage in the system (up to
the maximum tolerance of the coil) and the coil
should have low resistance; V
BATTERY
= 1.5 VDC
with a 470
H/4.9
coil are typical. The majority
of the current goes through the coil and typically
less than 1mA is required for V
DD
of the SP4428.
V
DD
can range from 1.5V to 1.7V; it is not necessary
that V
DD
=V
BATTERY
. Coils are also a function of the
core material and winding used -- performance
variances may be noticeable from different coil
suppliers. The Sipex SP4428 is final tested using
a 470
H/4.9
coil from Sumida. For suggested
coil sources see page 9.
The f
COIL
signal controls a switch that connects the
end of the coil at pin 3 to ground or to open circuit.
The f
COIL
signal is a 90% duty cycle signal switching
at the oscillator frequency. During the time when
the f
COIL
signal is high, the coil is connected from
V
BATTERY
to ground and a charged magnetic field is
created in the coil. During the low part of f
COIL
, the
ground connection is switched open, the field
collapses and the energy in the inductor is forced
to flow toward the lamp. f
COIL
will send 32 of these
charge pulses every half cycle (see figure 2
on page 7) to the lamp, each pulse increases the
voltage drop across the lamp in discrete steps. As
the voltage potential approaches its maximum, the
steps become smaller (see figure 1 on page 7).
The H-bridge consists of two SCR structures that
act as high voltage switches. These two switches
control the polarity of how the lamp is charged.
The SCR switches are controlled by the f
LAMP
signal which is the oscillator frequency divided by
64. For a 20kHz oscillator, f
LAMP
=300Hz.
Coil
Optional
1800pF CAP
LAMP
1
Pager
Application
C
OSC
V
SS
Coil
D1
HON
V
DD
EL1
EL2
0.1
F
5 FtL
1.5 SQ. IN.
Fast
Recovery
Diode
+
-
1.5 Volt
Battery
180pF
470
H
4.9 Ohms
Typical SP4428 Application Circuit
When the energy from the coil is released, a high
voltage spike is created triggering the SCR
switches. The direction of current flow is
determined by which SCR is enabled. One full
cycle of the H-bridge will create a voltage step
from ground to 80V (typical) on pins 5 and 6 which
are 180 degrees out of phase with each other
(see figure 3 on page 7). A differential view of the
outputs is shown in figure 4 on page 7. If Line
Noise is of concern it is advisable to add a
decoupling cap at V
DD
.
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 transformer, transistors,
and several resistors and capacitors. This approach
is large and bulky, and cannot be implemented in
most hand held equipment. Sipex 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.
SP4428DS/16
SP4428 Electroluminescent Lamp Driver
Copyright 2000 Sipex Corporation
5
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 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. There are many variables which can be
optimized for specific applications. Sipex supplies
characterization charts to aid the designer in
selecting the optimum circuit configuration
(see page 6 and 7).
SP4428DS/16
SP4428 Electroluminescent Lamp Driver
Copyright 2000 Sipex Corporation
6
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.
V
DD
=V
COIL
=1.5V; coil = 470
H/4ohm; C
OSC
= 180pf; C
INT
= 1800pf; C
LOAD
= 4.7nF
Total I
DD
vs. Temperature
Temperature (
O
C)
T
otal I
DD
(mA)
70
60
50
40
30
20
10
0
-40
0
25
70
85
Peak voltage vs. Temperature
V
DD
= 1.5V
P
eak-to-P
eak
v
olta
g
e
(V
olts)
200
150
100
50
0
-40
0
25
70
85
Temperature (
O
C)
Lamp Frequency vs. Temperature
Frequenc
y (Hz)
500
450
400
350
300
250
200
150
100
50
0
-40
0
25
70
85
Temperature (
O
C)
SP4428DS/16
SP4428 Electroluminescent Lamp Driver
Copyright 2000 Sipex Corporation
7
16 coil pulses per half cycle; 94% duty cycle.
EL1 Output
-EL2 Output
V
PEAK
=80V (typical)
EL1 output; 32 charge steps per half cycle
EL1 Output
-EL2 Output
V
PP
=160V
(typical)
Differential representation EL
12
.
Figure 1. EL output voltage in discrete steps at EL1 output
Figure 2. Voltage pulses released from the coil to the EL driver circuitry
Figure 3. EL voltage waveforms from the EL1 and EL2 outputs
Figure 4. EL differential output waveform of the EL1 and EL2 outputs
SP4428DS/16
SP4428 Electroluminescent Lamp Driver
Copyright 2000 Sipex Corporation
8
Figure 5. Bonding Diagram
D
A
P
N
I
P
X
Y
N
O
H
8
5
.
2
2
8
-
5
.
3
9
3
V
D
D
7
0
.
5
0
2
5
.
8
1
4
1
L
E
6
0
.
6
9
7
5
.
9
4
3
2
L
E
5
5
.
0
7
8
5
.
9
1
P
A
C
4
5
.
0
7
8
5
.
9
8
1
-
L
I
O
C
3
5
.
5
8
7
5
.
9
8
3
-
V
S
S
2
5
.
5
7
1
5
.
0
2
4
-
C
C
S
O
1
0
.
8
4
8
-
0
.
6
0
1
-
NOTES:
1. Dimensions are in Microns unless otherwise noted.
2. Bonding pads are 125 X 125 typical.
3. Outside dimensions are maximum, including scribe area.
4. Die thickness is 380
25 microns.
5. Pad center coordinates are relative to die center.
6. Die size (step size): 81 X 46 mils
BONDING DIAGRAM
EL1
CAP
C
OSC
COIL
EL2
V
DD
HON
V
SS
X
Y
SP4428DS/16
SP4428 Electroluminescent Lamp Driver
Copyright 2000 Sipex Corporation
9
Coilcraft USA
Ph: (847) 639-6400
Fax: (847) 639-1469
Coilcraft Europe
Ph: 44 01236 730595
Fax: 44 01236 730627
Coilcraft Taiwan
Ph: 886/2/264-3646
Fax: 886/2/270-0294
Coil Craft Singapore
Ph: 65 296-6933
Fax: 465 296-4463 #382
Part No. DO1608C-474
470
H, 3.60 ohm
.175
Max
Max
.260
6.60
Coil Manufacturers
New Coils
Coilcraft Hong Kong
Ph: 852 770-9428
Fax: 852 770-0729
(All Dimensions in mm)
.155
Dia
Max
.115
(All Dimensions in mm)
KOA Speer Electronics, Inc.
Ph: 814-362-5536
Fax: 814-362-8883
Part No. LPC4045TE471K
470
H, 4.55 ohm
4.5 Max
4.0
0.2
4.5
5.0
0.3
5.0
0.3
5.7
0.3
4.7
0.3
(All Dimensions in mm)
muRata USA
Ph: (770) 436-1300
Fax: (770) 436-3030
muRata Europe
Ph: 011-4991166870
Fax: 011-49116687225
muRata Taiwan Electronics
Ph: 011 88642914151
Fax: 011 88644252929
muRata Electronics
Singapore
Ph: 011 657584233
Fax: 011 657536181
muRata Hong Kong
Ph: 011-85223763898
Fax: 011 852237555655
Part No. LQN4N471K04
470
H, 11.5 ohm
Part No. 667MA471N
470
H, 1.90 ohm
(All Dimensions in mm)
7.3
0.2
(All Dimensions in mm)
4.4 Max
4.4 Max
Sumida Electric Co., LTD.
USA
Ph: (847) 956-0666
Fax: (847) 956-0702
Sumida Electric Co., LTD.
Japan
Ph: 03-3607-5111
Fax: 03-3607-5144
Sumida Electric Co., LTD.
Singapore
Ph: 2963388
Fax: 2963390
Sumida Electric Co., LTD.
Hong Kong
Ph: 28806688
Fax: 25659600
Part No. CDRH74-471MC
470
H, 3.01 ohm
Toko America Inc. USA
Ph: (847) 297-0070
Fax: (847) 699-7864
Toko Inc. Europe
Ph: (0211) 680090
Fax: (0211) 679-9567
Toko Inc. Japan
Ph: 03 3727 1161
Fax: 03 3727 1176
Toko Inc. Singapore
Ph: (255) 4000
Fax: (250) 8134
Toko Inc. Hong Kong
Ph: 2342-8131
Fax: 2341-9570
7.3
4.5
Max
2.75 Max
EL Lamp manufacturers
Leading Edge Ind. Inc.
11578 Encore Circle
Minnetonka, MN 55343
Phone 1-800-845-6992
Midori Mark Ltd.
1-5 Komagata 2-Chome
Taita-Ku 111-0043 Japan
Phone: 81-03-3848-2011
Luminescent Systems inc. (LSI)
101 Etna Road
Lebanon, NH. 03766-9004
Phone: (603) 448-3444
Fax: (603) 448-33452
EL polarizers/transflector
manufacturers
Nitto Denko
Yoshi Shinozuka
Bayside Business Park 48500
Fremont, CA 94538
Phone: 510 445-5400
Fax: 510 445-5480
Top Polarizer- NPF F1205DU
Bottom - NPF F4225
or (F4205) P3 w/transflector
Transflector Material
Astra Products
Mark Bogin
P.O. Box 479
Baldwin, NJ 11510
Phone (516)-223-7500
Fax (516)-868-2371
NEC Corporation
Yumi Saskai
7-1, Shiba 5 Chome, Minato-ku,
Tokyo 108-01, Japan
Phone: (03) 3798-9572
Fax: (03) 3798-6134
Seiko Precision
Shuzo Abe
1-1, Taihei 4-Chome,
Sumida-ku, Tokyo, 139 Japan
Phone: (03) 5610-7089
Fax: (03) 5610-7177
Gunze Electronics
2113 Wells Branch Parkway
Austin, TX 78728
Phone: (512) 752-1299
Fax: (512) 252-1181
SP4428DS/16
SP4428 Electroluminescent Lamp Driver
Copyright 2000 Sipex Corporation
10
P
W
1
0.228/0.244
0.150/0.157
0.189/0.197
0.014/0.019
0.050 BSC
0.053/0.069
SP4428
Pkg.
Minimum qty per reel
Standard qty per reel
Maximum qty per reel
CN
500
2500
3000
95 NSOIC SP4428 per tube, no minimum quantity
NSOIC-8 13" reels: P=8mm, W=12mm
All package dimensions in inches
8-pin NSOIC
SP4428DS/16
SP4428 Electroluminescent Lamp Driver
Copyright 2000 Sipex Corporation
11
ORDERING INFORMATION
Model
Temperature Range
Package Type
SP4428CN . ............................................. 0C to +70C ........................................... 8-Pin NSOIC
SP4428NEB ............................................................................................ NSOIC Evaluation Board
Sipex Corporation reserves the right to make changes to any products described herein. Sipex does not assume any liability arising out of the
application or use of any product or circuit described herein; neither does it convey any license under its patent rights nor the rights of others.
Corporation
SIGNAL PROCESSING EXCELLENCE
Please consult the factory for pricing and availability on a Tape-On-Reel option.
Sipex Corporation
Headquarters and
Sales Office
22 Linnell Circle
Billerica, MA 01821
TEL: (978) 667-8700
FAX: (978) 670-9001
e-mail: sales@sipex.com
Sales Office
233 South Hillview Drive
Milpitas, CA 95035
TEL: (408) 934-7500
FAX: (408) 935-7600
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