SP4427
Electroluminescent Lamp Driver
Dual Oscillators with High Drive Capability
■ DC to AC Inverter for EL Backlit
Display Panels
■ Low Voltage, Single Battery Operation
(vbat > 1.1 Vdc)
■ Dual Oscillator Operation for
Application Flexibility
■ Low Current Standby Mode
APPLICATIONS
■ Pagers ■ PDA's ■ Backlit
LCD Displays
DESCRIPTION…
The SP4427 is a high voltage output DC-AC converter that can operate from a single 1.5 Vdc
battery supply. The SP4427 is capable of supplying up to 250 Vpp signals, making it ideal for
driving electroluminescent lamps. The device features 100nA (typ) standby current, for use
in low power portable products. One external inductor is required to generate the high voltage
charge, and two external capacitors are used to select the oscillator and lamp frequencies.
The SP4427 is offered in both an 8 pin narrow SOIC or micro SOIC package. For delivery
in die form, please consult the factory.
6
VDD
COIL
7
HON
EN
8 Bit Counter
1
Cosc
Losc
8
H
Bridge
Coil OSC
3
EL1
5
EL2
Lamp OSC
4
VSS
2
Block Diagram
SP4427DS/01
SP4427 Electroluminescent Lamp Driver
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© Copyright 1997 Sipex Corporation
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.
Vdd............................................................................................................7.0V
Input Voltages/Currents
HON (pin1)..........................................-0.5V to (Vdd+0.5V)
COIL (pin3)............................................................100mA
Lamp Outputs.............................................................................250Vpp
Storage Temperature....................................................-65˚C to +150˚C
Power Dissipation.......................................................................200mW
SPECIFICATIONS
(T= 25°C; Vdd = 1.5V; Lamp Capacitance = 8000pF; Coil = 20 mH at 70 Ohms; Coil OSC = 220pF, Lamp OSC = 1800pF unless otherwise noted)
PARAMETER
INPUT CHARACTERISTICS
MIN.
Supply Voltage
Total Supply Current
Quiescent Supply Current
Hon Voltage On
Hon Current On
Hon Voltage Off
1.1
INDUCTOR DRIVE
Peak Current
Pulse Rate
Duty Cycle
LAMP OUTPUT
Differential Voltage
Frequency
Lamp Capacitance
TYP.
MAX.
UNIT
CONDITIONS
1.5
10
100
15
200
Volts
mA
nA
Vdd= 1.5V ±5%; Hon= 1.5V
Vdd= 1.5V ±5%; Hon= 0.2V
10
<Vdd/2
Volts
µA
Volts
6
85
mA
kHz
%
Vdd
60
5
75
3
70
80
150
110
250
8000
350
Internal pulldown
Vpp
Hz
pF
Bonding Diagram:
ELEN
VDD
CAP 1
EL 1
CAP 2
EL 2
SP4427
664A
VSS
COIL
PAD
X
Y
EL1
EL2
COIL
VSS
HON
CAP2
CAP1
VDD
586.0
586.0
586.0
80.0
562.5
565.0
562.5
588.0
107.0
-143.0
-376.0
-417.0
-397.0
-118.0
114.5
417.0
NOTES:
1. Dimensions are in Microns unless otherwise noted.
2. Bonding pads are 125x125 typ.
3. Outside dimensions are maximum, including scribe area.
4. Die thickness is 380 +/- 25 microns (15 mils +/- 1).
5. Pad center coordinates are relative to die center.
6. Die size 1498 x 1168 ( 59 x 46 mils).
SP4427DS/01
SP4427 Electroluminescent Lamp Driver
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© Copyright 1997 Sipex Corporation
THEORY OF OPERATION
PIN DESCRIPTION
SP4427CN
1
2
3
4
The SP4427 is made up of three basic circuit
elements: an oscillator, coil, and switched H-bridge
network. The oscillator portion of the circuit is
divided into two precision oscillators. The
oscillators set the coil and lamp frequencies
independently. This allows for the arbitrary setting
of the coil/lamp frequency ratio. The coil frequency
can be selected for maximum energy transfer per
cycle for a given external coil value. The coil
oscillator is set at 75% duty cycle and the lamp
oscillator is set at 50% duty cycle for minimum DC
offset across the EL lamp.
8
7
6
5
Pin 1 – Cosc- Connect Cap1 from Vss to pin 1 to
set oscillator frequency.
Pin 2 – Vss- Power supply common, connect to
ground.
An external capacitor connected between pin 8
and VSS allows the user to vary the lamp oscillator
frequency from 75Hz to 350Hz. Likewise, an
external capacitor connected between pin 1 and
VSS allows the user to vary the coil oscillator
frequency from 3.5kHz to 50kHz. The graphs on
page 6 show the relationship between oscillators
(LOSC and COSC) and their respective capacitor
values.
Pin 3 – Coil- Coil input, connect coil from
Vbattery to pin 3.
Pin 4 – EL2- Lamp driver output1, connect to
EL lamp.
Pin 5 – EL1- Lamp driver output2, connect to
EL lamp.
Pin 6 – Vdd- Power supply for driver, connect to
system Vdd.
The coil is an external component connected from
Vbattery to pin 3 of the SP4427. Energy is developed
in the coil according to the equation EL=1/2LI2
where the current I is defined as I = (Vbattery-IRVOL)/RT. In order to maximize the energy produced
by the coil Vbattery should represent the largest
Pin 7 – HON- Enable for driver operation,
high = active; low = inactive.
Pin 8 – Losc- Connect Cap2 from Vss to pin 8 to
set lamp frequency.
Vbat
+
Vbat
+
L1
20 mH/70Ω
0.1µF
Place as close
as possible to
IC pin 6
Low
ESR CAP
6
3
OSC 1
200 pF
1
5
Coil
EL
DRIVER
OSC 2
1800 pF
8
EL Lamp
4
Lamp
2
HON
7
SP4427
SP4427 Schematic
SP4427DS/01
SP4427 Electroluminescent Lamp Driver
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© Copyright 1997 Sipex Corporation
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 number of
voltage steps from ground to 55V (typ) on pins 4
and 5 which are 180 degrees out of phase with each
other (see figure 3 page 6). A differential view of
the outputs is shown in figure 4 on page 6. If Line
Noise is of concern it is advisable to add a
decoupling cap at Vdd (low ESR type).
voltage in the system (up to the maximum tolerance
of the coil) and the coil should have low resistance
and high inductance; Vbattery= 1.5 VDC with a
20mH/70Ω coil are typical. The majority of the
current goes through the coil and typically less
than 1mA is required for Vdd of the SP4427. Vdd
can range from 1.1V to 5V; it is not necessary that
Vdd=Vbattery. Coils are also a function of the core
material and winding used -- performance variances
may be noticeable from different coil suppliers.
The Sipex SP4427 is final tested using a 20mH/
70Ω coil from CTC. For suggested coil sources see
page 7.
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. All that is required is
one external inductor and capacitor.
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. During
the time when the Fcoil signal is high, the coil is
connected from Vbattery to ground and a charged
magnetic field is created in the coil. During the low
part of Fcoil , the ground connection is switched
open, the field collapses and the energy in the
inductor is forced to flow toward the
high voltage H-bridge switches. Fcoil will send
as many charge pulses as possible in 1 Lamp Cycle
{Number of Coil pulses in 1 lamp cycle =
Coil Freq
Lamp Freq (2) }(see figure 2 page 6). 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 page 6).
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 Flamp signal
which is the oscillator frequency divided by 256.
For a 64kHz oscillator, Flamp =256Hz.
CAP 1 = 220 pF
CAP 2 = 1800 pF
1.5 Volt
Application
-
1
Cosc Losc
Vss
Hon
Coil
Vdd
EL2
EL1
3.FtL
LAMP
Coil
+
5mH/18Ω
0.1µF
Electroluminescent backlighting is ideal when used
with LCD displays, keypads, or other backlit
readouts. Its main use is to illuminate displays in
1.6 SQ. IN.
Typical SP4427CN Application Circuit
SP4427DS/01
SP4427 Electroluminescent Lamp Driver
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© Copyright 1997 Sipex Corporation
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. 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.
SP4427DS/01
SP4427 Electroluminescent Lamp Driver
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© Copyright 1997 Sipex Corporation
Vpeak=80V (typ)
EL1 output; charge steps per half cycle based on # of coil pulses per half cycle.
Figure 1.
coil freq.
Number of coil pulses in 1 lamp cycle =
lamp freq. (2)
; 90% duty cycle.
Figure 2.
EL1 Output
-EL2 Output
Figure 3.
EL1 Output
Vpp=160V (typ)
-EL2 Output
Differential Representation E12.
Figure 4.
SP4427DS/01
SP4427 Electroluminescent Lamp Driver
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© Copyright 1997 Sipex Corporation
HITACHI METALS Ltd.
Kishimoto Bldg.
2-1, Marunouchi 2-Chome,
Chiyoda-Ku, Tokyo Japan
Phone: 3-3284-4936
Fax: 3-3287-1945
Mr. Noboru Abe
Spec.9 mH ±30% 42 ohm (Max)
Model: MD 735L902B
Singapore
Mr Stan kaiko,
Mr. Hiroshi Kai
Phone: 222-8077
Fax: 222-5232
San Jose, CA
Mr. Kent Oda
Ph: 408 436-9505
Fx: 408 436-9601 6.8
±0.3
7 ±0.5
Hong Kong
Mr Mori Ota
Phone: 2724-4188
(All Dimensions in mm)
Fax: 2311-2095
Sankyo Shoji Co. (HK)
RM 28, 9/il Thriving Ind. Centre
Tsuen Wan, N.T.
Hong Kong
Phone: 8522 414 9268
Fax: 8522 413 6040
Contact: Mr. K.M. Chang
Inductance: 29mH ±20 %
Resistance: 62 Ohms ±10% @ 25˚C
Part Number SK-121
Sankyo Shoji Co. (HK)
RM 28, 9/il Thriving Ind. Centre
Tsuen Wan, N.T.
Hong Kong
Phone: 8522 414 9268
Fax: 8522 413 6040
Contact: Mr. K.M. Chang
Inductance: 65mH ±15mH
Resistance: 270 Ohms ±15% @ 25˚C
Part Number SK-80
CTC Coils LTD (HK)
Flat L-M 14 Fl, Haribest Ind'l Bldg.
45-47 Au Pul Wan Street
Fo Tan Shatin. N.T., Hong Kong
Phone: 85 2695 4889
Fax: 85 2695 1842
Contact: Alfred Wong cc Marine Au
Inductance: 20 mH ±10%
Resistance: 65 Ohms Max
Model Number: CH5070AS-203K-006
Sipex No. S51208-M-1021-Sipex
3.3
±0.3
6 ±0.3
8.1
±0.2
11
±0.2
1.5
(All Dimensions in mm)
3.3
±0.2
3.6
5.6 Max.
0.8
2.4
(All Dimensions in mm)
25 ± 2.0
2.5
6.5 Max
9.0 Max
All dimensions in mm
Mark Technology: North American stocking distributor for Sankyo and CTC
Phone: 905-891-0165 FAX: 905-891-8534.
EL polarizers/transflector
manufacturers
Nitto Denko
Yoshi Shinozuka
56 Nicholson Lane
San Jose, CA. 432-5480
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
SP4427DS/01
EL Lamp manufacturers
Leading Edge Ind. Inc.
11578 Encore Circle
Minnetonka, MN 55343
Phone 1-800-845-6992
NEC Corporation
Yumi Saskai
7-1, Shiba 5 Chome, Minato-ku,
Tokyo 108-01, Japan
Phone: (03) 3798-9572
Fax: (03) 3798-6134
Nippon Graphite
Peter J. Opdahl
123 NW 13th Street #308
Boca Raton, FL 33432
Phone: (407) 392-2555
Fax: (407) 392-0807
Seiko Precision
Shuzo Abe
1-1, Taihei 4-Chome,
Sumida-ku, Tokyo, 139 Japan
Phone: (03) 5610-7089
Fax: (03) 5610-7177
Luminescent Systems inc. (LSI)
101 Etna Road
Lebanon, NH. 03766-9004
Phone: (603) 448-3444
Fax: (603) 448-33452
MKS
7 N. Industrial Blvd
Bridgeton, NJ. 08302
Phone: (609) 451-5545
Fax: (609) 451-9096
SP4427 Electroluminescent Lamp Driver
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© Copyright 1997 Sipex Corporation
0.0256
BSC
12.0˚
±4˚
0.012
±0.003
0.189/0.197
SP4427
0.150/0.157
0.228/0.244
0.0965
±0.003
R .003
0.053/0.069
SP4427
0.118
±0.002
0.014/0.019
0.050 BSC
1
0.16
±0.003
12.0˚
±4˚
0.01
0.020
0.020
1
2"
0.008
3.0˚
±3˚
0.0215
±0.006
0.037
Ref
2
0.116
±0.004
0.034
±0.002
0.116
±0.004
0.040
±0.002
0.013
±0.005
0.118
±0.002
2"
0˚ - 6˚
0.006
±0.006
0.006
±0.006
0.118
±0.004
0.004
±0.002
100 SP4427 die per waffle pack
95 SP4427 per tube, no minimum quantity
50 SP4427 per tube
P
W
NSOIC-8 13" reels: P=8mm, W=12mm
Minimum qty per reel
CN
CU
SP4427DS/01
Standard qty per reel
Maximum qty per reel
1500
1500
2500
3000
500
500
SP4427 Electroluminescent Lamp Driver
8
© Copyright 1997 Sipex Corporation
ORDERING INFORMATION
Model
Temperature Range
Package Type
SP4427CN . ............................................. 0˚C to +70˚C ........................................... 8-Pin NSOIC
SP4427CN/TR ......................................... 0˚C to +70˚C ........................................... 8-Pin NSOIC
SP4427CX ............................................... 0˚C to +70˚C .......................................................... Die
SP4427CU . ............................................. 0˚C to +70˚C ........................................... 8-Pin USOIC
SP4427CU/TR ......................................... 0˚C to +70˚C ........................................... 8-Pin USOIC
SP4427NEB ............................................................................................ NSOIC Evaluation Board
SP4427UEB ............................................................................................ USOIC Evaluation Board
Corporation
SIGNAL PROCESSING EXCELLENCE
Sipex Corporation
US Regional Sales Offices:
European Sales Offices:
Far East:
22 Linnell Circle
Billerica, MA 01821
TEL: (508) 667-8700
FAX: (508) 670-9001
22 Linnell Circle
Billerica, MA 01821
GERMANY:
Sipex GmbH
Gautinger Strasse 10
82319 Starnberg
TEL: 49.81.51.89810
FAX: 49.81.51.29598
JAPAN:
Nippon Sipex Corporation
Yahagi No. 2 Building
3-5-3 Uchikanda, Chiyoda-ku
Tokyo 101, Japan
TEL: 011.81.3.3256.0577
FAX: 011.81.3.3256.0621
491 Fairview Way
Milpitas, CA 95035
TEL: (408) 945-9080
FAX: (408) 946-6191
EASTERN U.S.:
TEL: (508) 667-8700
FAX: (508) 670-9001
WESTERN U.S.:
TEL: (508) 667-8700
FAX: (508) 670-9001
FRANCE:
Sipex
30 Rue du Morvan, SILIC 525
94633 Rungis Cedex
TEL: 33.1.4687.8336
FAX: 33.1.4560.0784
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 hereing; neither does it convey any license under its patent rights nor the rights of others.
SP4427DS/01
SP4427 Electroluminescent Lamp Driver
9
© Copyright 1997 Sipex Corporation