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SP4426 Electroluminescent Lamp Driver with High Output Drivers
s 2.2V-6.0V Battery Operation s DC to AC Inverter for EL Backlit Display Panels s Externally Adjustable Internal Oscillator s Low Current Standby Mode
APPLICATIONS
s HPC's s PDA's s Pen Tablets s Backlit LCD Displays
DESCRIPTION...
The SP4426 is a high voltage output DC-AC converter that can operate from a 2.2V-6.0V power supply. The SP4426 is capable of supplying up to 300 Vpp signals, making it ideal for driving electroluminescent lamps. The device features 100 nA (typ) 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 select the oscillator and Lamp frequencies. The SP4426 is offered in a 14 pin narrow SOIC. For delivery in die form, please consult the factory.
11 6 D1 VDD COIL 1 HON EN 8 Bit Counter 14 CAP1 CAP1 H Bridge EL1 7
5
CAP2 12
CAP2 VSS 3
EL2 8
Block Diagram
SP4426DS/01 SP4426 Electroluminescent Lamp Driver (c) Copyright 1997 Sipex Corporation
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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)..............................................................60mA Lamp Outputs.............................................................................250Vpp Storage Temperature....................................................-65C to +150C Power Dissipation.......................................................................200mW
SPECIFICATIONS
(T= 25C; Vdd = 3.0V; Lamp Capacitance = 6000pF; Coil = 9 mH (RS = 30); Cosc = 150pF unless otherwise noted)
PARAMETER INPUT CHARACTERISTICS
MIN.
TYP.
MAX.
UNIT
CONDITIONS
Supply Voltage Total Supply Current
2.2
3.0 8 15 10 0.3 76.8
6.0 15 50 200 1
Volts mA mA nA A kHz Volts A A Volts Volts mA kHz % Vpp Hz Hz pF
Quiescent Supply Current
Clock Frequency Hon Voltage On Hon Current On Hon Voltage Off INDUCTOR DRIVE Peak Current Pulse Rate Duty Cycle LAMP OUTPUT Differential Voltage Frequency Lamp Capacitance
Vdd-.5 25 50
Vdd 60 120 Vdd-2 Vdd-3 60
Vdd= 3.0V 5%; Hon= 3.0V Vdd= 6.0V 5%; Hon= 6.0V 150 in series with coil Vdd= 3.0V 5%; Hon= 0V Vdd= 6.0V 5%; Hon= 0V 150 in series with coil Cosc=150pF; Vdd = 3.0V, (fL x 256) Vdd = 3.0V Vdd = 6.0V Vdd = 3.0V Vdd = 6.0V
9.6 94 120 200 225 160 300 300 6000
(f L x 32)
400 450
Vdd = 3.0V Vdd = 6.0V
SP4426DS/01
SP4426 Electroluminescent Lamp Driver
(c) Copyright 1997 Sipex Corporation
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PIN DESCRIPTION
1 2 3 4 5 6 7 14 13 12 11 10 9 8
THEORY OF OPERATION The SP4426 is made up of three basic circuit elements, an oscillator, coil, 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 Vss allows the user to vary the oscillator frequency. The graphs on page 6 show the relationship between Cosc and lamp output voltage. For a given choice of coil inductance there will be an optimum COSC Cap valve that gives the maximum light output. The suggested oscillator frequency is 20kHz (Cosc=180pF). The oscillator output is internally divided to create two internal control signals, Fcoil and Flamp. The oscillator output is internally divided down by 8 flip flops, a 64kHz signal will be divided into 8 frequency levels; 32kHz, 16kHz, 8kHz, 4kHz, 2kHz, 1kHz, .5kHz, .25 kHz. The third flip flop output (8KHz) is used to drive the coil (see figure 2 on page 8) and the eighth flip flop output (256Hz) is used to drive the lamp. Although the oscillator frequency can be varied to optimize the lamp output, the ratio of Fcoil/Flamp will always equal 32. The on-chip oscillator of the SP4426 can be overdriven with an external clock source by removing the COSC capacitor and connecting a clock source to pin 8. The clock should have a 50%
Vbattery 9MH/35 IN4148
Pin 1-- HON- Enable for driver operation, high=active; low=inactive Pin 2-- N/C- No connect Pin 3-- Vss- Power supply common, connect to ground. Pin 4-- N/C- No connect Pin 5-- Coil- Coil Pin 6-- D1- Diode cathode connection Pin 7-- EL1- Lamp driver output 1, connect to EL lamp Pin 8-- EL2- Lamp driver output 2, connect to EL lamp Pin 9-- N/C- No connect Pin 10-- N/C- No connect Pin 11-- Vdd- Power supply for driver, connect to system Vdd. Pin 12-- C2- Capacitor input 2, connect to Cosc Pin 13-- N/C- No connect Pin 14-- C1- Capacitor input 1, connect to Cosc
.1F
11 Vdd 1M 11 C1 OSC Cap1
SP4426
Vdd
Optional 1,800pF 6 D1
1 Hon
5 Coil
F coil
SCR1
SCR2
180pF Cap2 12 C2
Q Flamp
FF1
FF6
Q
Flamp
Vss 3
EL1 7
EL2 8
EL Lamp
SP4426 Schematic
SP4426DS/01 SP4426 Electroluminescent Lamp Driver (c) Copyright 1997 Sipex Corporation
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duty cycle and range from Vdd-1V to ground. An external clock signal may be desirable in order to synchronize any parasitic switching noise with the system clock. The maximum external clock frequency that can be supplied is 400kHz. The coil is an external component connected from Vbattery to pin 9 of the SP4426. Energy is stored in the coil according to the equation EL=1/2LI2 where I, the the first approximation is (Vbat-VCE)RL. Where VCE is approximately ) 0.5 volts for the internal coil driver transistor, and RL is the series resistance of the inductor. In order to maximize the energy stored in the inductor and subsequently recovered during the switching off of the coil transistor, it is expedient to use the highest value battery, the largest inductor with the smallest series resistance that the system constraints will permit. This energy recovery is directly related to the brightness of the lamp output. There are great variations among coils; caused by magnetic material differences, winding differences and parasitic capacitance. The Sipex SP4426 is final tested using a 9mH/35 coil from Hitachi. For suggested coil sources see page 8. The supply Vdd can range from 2.2 to 6.0V. It is not necessary that Vdd=Vbattery. Vbattery should not exceed max coil current specification. The majority of the current goes through the coil and is typically much greater than Idd.
The Fcoil signal controls a switch that connects the end of the coil at pin 5 to ground or to open circuit. The Fcoil signal is a 94% duty cycle signal switching at the oscillator frequency. 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 lamp. Fcoil will send 16 of these charge pulses (see figure 2 page 8) 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 page 8). For maximum performance a fast recovery diode is recommended and should be connected between pins 5 and 6 (cathode side). The low reverse voltage capacitance of the fast recovery diode minimizes the voltage that is charged and discharged across it and this increases the energy transferred to the lamp. 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 64. For a 20kHz oscillator, Flamp =300Hz.
PDA Application
Switch
1
HON N/C Vss N/C Cosc
C1 N/C C2 Vdd N/C N/C EL2
180pF
+
Coil
3 Volt Battery
Coil 9mH/35
-
Coil D1
IN418
EL1
EL LAMP
6 SQ. IN.
Optional 1800pF
Typical SP4426 Application Circuit
SP4426DS/01
SP4426 Electroluminescent Lamp Driver
(c) Copyright 1997 Sipex Corporation
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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 (typ) on pins 5 and 6 which are 180 degrees out of phase with each other (see figure 3 page 8). A differential view of the outputs is shown in figure 4 on page 8. If Line Noise is of concern it is advisable to add a decoupling cap at Vdd. 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. 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, 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 (see page 6 and 7).
SP4426DS/01
SP4426 Electroluminescent Lamp Driver
(c) Copyright 1997 Sipex Corporation
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SP4426DS/01
SP4426 Electroluminescent Lamp Driver
(c) Copyright 1997 Sipex Corporation
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SP4426DS/01
SP4426 Electroluminescent Lamp Driver
(c) Copyright 1997 Sipex Corporation
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Vpeak=80V (typ)
EL1 output; 16 charge steps per half cycle
Figure 1.
16 coil pulses per half cycle; 94% duty cycle.
Figure 2.
EL1 Output
-EL2 Output
Figure 3.
EL1 Output Vpp=160V (typ)
-EL2 Output Differential representation EL12.
Figure 4.
SP4426DS/01
SP4426 Electroluminescent Lamp Driver
(c) Copyright 1997 Sipex Corporation
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Coil Manufacturers
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 Coilcraft Hong Kong Ph: 852 770-9428 Fax: 852 770-0729
New Coils
.260 Max 6.60 .175 Max 4.45 .155 Dia 3.94 .115 Max 2.92
Part No. DO1608C-474 470H, 3.60 ohm
(All Dimensions in mm) 5.0 0.3
4.7 0.3
muRata USA Ph: (770) 436-1300 Fax: (770) 436-3030 muRata Europe Ph: 011-4991166870 Fax: 011-49116687225
muRata Taiwan Electronics muRata Hong Kong Ph: 011 88642914151 Ph: 011-85223763898 Fax: 011 88644252929 Fax: 011 852237555655 muRata Electronics Singapore Ph: 011 657584233 Fax: 011 657536181 Part No. LQN4N471K04 470H, 11.5 ohm
5.0 0.3
5.7 0.3 (All Dimensions in mm)
KOA Speer Electronics, Inc. Ph: 814-362-5536 Fax: 814-362-8883 Part No. LPC4045TE471K 470H, 4.55 ohm
4.0 0.2 4.5 Max (All Dimensions in mm)
4.5 .02
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
7.3 0.2 7.3 0.2 4.5 Max
Part No. CDRH74-471MC 470H, 3.01 ohm
(All Dimensions in mm)
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 Part No. 667MA471N 470H, 1.90 ohm
4.4 Max
2.75 Max 4.4 Max
(All Dimensions in mm)
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
SP4426DS/01
EL Lamp manufacturers
Leading Edge Ind. Inc. 11578 Encore Circle Minnetonka, MN 55343 Phone 1-800-845-6992 Nippon Graphite Peter J. Opdahl 123 NW 13th Street #308 Boca Raton, FL 33432 Phone: (407) 392-2555 Fax: (407) 392-0807 Luminescent Systems inc. (LSI) 101 Etna Road Lebanon, NH. 03766-9004 Phone: (603) 448-3444 Fax: (603) 448-33452
SP4426 Electroluminescent Lamp Driver
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 MKS 7 N. Industrial Blvd Bridgeton, NJ. 08302 Phone: (609) 451-5545 Fax: (609) 451-9096
(c) Copyright 1997 Sipex Corporation
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0.337/0.344
0.150/0.157
SP4426
0.228/0.244
0.053/0.069
0.014/0.019 0.050 BSC
1
2"
2"
100 SP4426 die per waffle pack
50 SP4426 per tube, no minimum quantity
P
W
NSOIC-8 13" reels: P=8mm, W=12mm Minimum qty per reel CN 500
Standard qty per reel 1500
Maximum qty per reel 2500
SP4426DS/01
SP4426 Electroluminescent Lamp Driver
(c) Copyright 1997 Sipex Corporation
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ORDERING INFORMATION
Model Temperature Range Package Type SP4426CN . ............................................. 0C to +70C ......................................... 14-Pin NSOIC SP4426CN/TR ......................................... 0C to +70C ......................................... 14-Pin NSOIC SP4426CX ............................................... 0C to +70C .......................................................... Die SP4426NEB ............................................................................................ NSOIC Evaluation Board
Corporation
SIGNAL PROCESSING EXCELLENCE
Sipex Corporation 22 Linnell Circle Billerica, MA 01821 TEL: (508) 667-8700 FAX: (508) 670-9001 491 Fairview Way Milpitas, CA 95035 TEL: (408) 945-9080 FAX: (408) 946-6191 US Regional Sales Offices: 22 Linnell Circle Billerica, MA 01821 EASTERN U.S.: TEL: (508) 667-8700 FAX: (508) 670-9001 WESTERN U.S.: TEL: (508) 667-8700 FAX: (508) 670-9001 European Sales Offices: GERMANY: Sipex GmbH Gautinger Strasse 10 82319 Starnberg TEL: 49.81.51.89810 FAX: 49.81.51.29598 FRANCE: Sipex 30 Rue du Morvan, SILIC 525 94633 Rungis Cedex TEL: 33.1.4687.8336 FAX: 33.1.4560.0784 Far East: 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
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. SP4426DS/01 SP4426 Electroluminescent Lamp Driver (c) Copyright 1997 Sipex Corporation
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