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SP4428
Electroluminescent Lamp Driver High Drive Capability for Low Voltage Applications
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
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 VPP (typical), making it ideal for driving electroluminescent lamps. The device features 1A (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.
COSC VSS COIL D1
1 2 3 4 SP4428
8 7 6 5
HON VDD EL1 EL2
Block Diagram
SP4428DS/16 SP4428 Electroluminescent Lamp Driver (c) Copyright 2000 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. TA= +25C unless otherwise noted VDD............................................................................................................5V Input Voltages/Currents HON (pin1).........................................-0.5V to (VDD+0.5V) COIL (pin3)............................................................100mA Lamp Outputs.............................................................................230VPP Storage Temperature....................................................-65C to +150C Power Dissipation Per Package 8-pin NSOIC (derate 6.14mW/oC above +70oC).................................500mW
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.
SPECIFICATIONS
(T= 25C; VDD = 1.5V; Lamp Capacitance = 4.7nF; Coil = 470H at 4.9 Ohms; COSC = 180pF unless otherwise noted) CINT = 1800pF
PARAMETER Supply Voltage, VDD Supply Current, ICOIL+IDD Coil Voltage, VCOIL HON Input Voltage, VHON LOW: EL off HIGH: EL on HON Current, EL on Shutdown Current, ISD=ICOIL+IDD INDUCTOR DRIVE Coil Frequency, fCOIL Coil Duty Cycle Peak Coil Current, IPK-COIL EL LAMP OUTPUT EL Lamp Frequency, fLAMP
MIN. 1.1
TYP. 1.5 35 45
MAX. 1.7 50 80 1.7
UNITS V mA V
CONDITIONS
VDD=1.1V, VHON=1.1V VDD=1.5V, VHON=1.5V
VDD -0.25 VDD-0.25 0 VDD 3 0.5
0.25V VDD+0.25 15 10
V A A
internal pulldown, VHON=VDD=1.5V VHON=0V
28.8 90 100
kHz % mA Guaranteed by design.
150 300 150 90 120
450
500 550 750
Hz
TAMB=+25OC, VDD=1.1V TAMB=+25OC, VDD=1.5V TAMB=-40OC to +85OC, VDD=1.5V VDD=1.1V VDD=1.5V
Peak to Peak Output Voltage
120 160
VPP
SP4428DS/16
SP4428 Electroluminescent Lamp Driver
(c) Copyright 2000 Sipex Corporation
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PIN DESCRIPTION
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 VSS allows the user to vary the oscillator frequency. For a given choice of coil inductance there will be an optimum COSC Capacitor value that gives the maximum light output in a given lamp. The suggested oscillator frequency is 28.8kHz (COSC=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 fCOIL/fLAMP will always equal 64. The coil is an external component connected from VBATTERY 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=(VBATTERY-IR-VOL)/RT. In order to maximize the
1 2 3 4
8 7 6 5
Pin 1 - COSC- Connect CAP from VSS to Pin 1 to set Oscillator frequency. Pin 2 - VSS- Power supply common, connect to ground. Pin 3 - Coil- Coil input, connect coil from VBATTERY 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 - VDD- Power supply for driver, connect to system VDD. Pin 8 - HON- Enable for driver operation, high = active; low = inactive.
SP4428
VDD 7 VDD
VBATTERY
470H/4.9 IN4148 8 HON 1M 3 Coil 4
Optional 1,800pF
.1F
D1
1 COSC 180pF
OSC Cap1 fCOIL
SCR1 SCR2
fLAMP
Q
FF1
FF6
Q
fLAMP EL1 5 EL2 6
VSS 2
EL Lamp
SP4428 Schematic
SP4428DS/16 SP4428 Electroluminescent Lamp Driver (c) Copyright 2000 Sipex Corporation
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energy produced by the coil VBATTERY should represent the largest voltage in the system (up to the maximum tolerance of the coil) and the coil should have low resistance; VBATTERY= 1.5 VDC with a 470H/4.9 coil are typical. The majority of the current goes through the coil and typically less than 1mA is required for VDD of the SP4428. VDD can range from 1.5V to 1.7V; 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 SP4428 is final tested using a 470H/4.9 coil from Sumida. For suggested coil sources see page 9. 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. 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 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 fLAMP signal which is the oscillator frequency divided by 64. For a 20kHz oscillator, fLAMP=300Hz.
Pager Application
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 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.
0.1F 180pF 1.5 Volt Battery
1
COSC VSS Coil D1
Fast Recovery Diode
HON VDD EL1 EL2
5 FtL
Coil
Typical SP4428 Application Circuit
SP4428DS/16 SP4428 Electroluminescent Lamp Driver (c) Copyright 2000 Sipex Corporation
+ -
LAMP
1.5 SQ. IN.
470H 4.9 Ohms
Optional 1800pF CAP
4
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
(c) Copyright 2000 Sipex Corporation
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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.
VDD=VCOIL=1.5V; coil = 470H/4ohm; COSC = 180pf; CINT = 1800pf; CLOAD = 4.7nF
Total IDD vs. Temperature 70 60 50 40 30 20 10 0
Peak voltage vs. Temperature VDD = 1.5V
Peak-to-Peak voltage (Volts)
Total IDD (mA)
200 150 100 50 0 -40 0 25
O
-40
0 25 70 Temperature ( C)
O
85
70
85
Temperature ( C)
Lamp Frequency vs. Temperature
500 450 400 350 300 250 200 150 100 50 0
Frequency (Hz)
-40
0
25
O
70
85
Temperature ( C)
SP4428DS/16
SP4428 Electroluminescent Lamp Driver
(c) Copyright 2000 Sipex Corporation
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VPEAK=80V (typical)
EL1 output; 32 charge steps per half cycle
Figure 1. EL output voltage in discrete steps at EL1 output
16 coil pulses per half cycle; 94% duty cycle.
Figure 2. Voltage pulses released from the coil to the EL driver circuitry
EL1 Output
-EL2 Output
Figure 3. EL voltage waveforms from the EL1 and EL2 outputs
EL1 Output VPP=160V (typical) -EL2 Output Differential representation EL12.
Figure 4. EL differential output waveform of the EL1 and EL2 outputs
SP4428DS/16
SP4428 Electroluminescent Lamp Driver
(c) Copyright 2000 Sipex Corporation
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BONDING DIAGRAM X Y HON VDD EL1
PAD HON VDD EL1 EL2 PIN 8 7 6 5 4 3 2 1 X -822.5 205.0 796.0 870.5 870.5 785.5 175.5 -848.0 Y 393.5 418.5 349.5 19.5 -189.5 -389.5 -420.5 -106.0
COSC
EL2 CAP VSS COIL
CAP COIL VSS COSC
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
Figure 5. Bonding Diagram
SP4428DS/16
SP4428 Electroluminescent Lamp Driver
(c) Copyright 2000 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 .155 Dia .115 Max
Max
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
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 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 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
SP4428DS/16
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
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
SP4428 Electroluminescent Lamp Driver
(c) Copyright 2000 Sipex Corporation
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All package dimensions in inches 8-pin NSOIC
0.189/0.197
0.150/0.157
SP4428
0.228/0.244
0.053/0.069
0.014/0.019 0.050 BSC
1
95 NSOIC SP4428 per tube, no minimum quantity
P
W
NSOIC-8 13" reels: P=8mm, W=12mm Pkg. CN Minimum qty per reel 500 Standard qty per reel 2500 Maximum qty per reel 3000
SP4428DS/16
SP4428 Electroluminescent Lamp Driver
(c) Copyright 2000 Sipex Corporation
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ORDERING INFORMATION
Model Temperature Range Package Type SP4428CN . ............................................. 0C to +70C ........................................... 8-Pin NSOIC SP4428NEB ............................................................................................ NSOIC Evaluation Board
Please consult the factory for pricing and availability on a Tape-On-Reel option.
Corporation
SIGNAL PROCESSING EXCELLENCE
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
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.
SP4428DS/16
SP4428 Electroluminescent Lamp Driver
(c) Copyright 2000 Sipex Corporation
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