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SP4480
Dual Electroluminscent Lamp Driver
s Backlights Keypad & LCD With A Single El Driver s A Single External IC Drives Dual EL Lamps Simultaneously Or Independently s A Single Coil Drives Both EL Lamp s A Single Resistor Controls the Operating Frequency s DC-to-AC Inverter Produces Up To 200VP-P s Low Current Standby Mode Draws Less Than 1A s +2.2V to +6.0V Battery Operation
DESCRIPTION The SP4480 provides a designer with two electroluminescent lamp drivers for backlighting solutions. The EL lamp outputs operate in opposite phase so he SP4480 device can be easily implemented into applications driving two EL lamps simultaneously or driving double-sided, multi-color EL lamps. The integration of a dual EL lamp driver in a cost-effective single IC reduces component count and board space requirements. The SP4480 is ideal for portable applications such as cellular phones, pagers, PDAs, medical equipment, and other designs with liquid crystal displays, keypads, and backlit readouts. The SP4480 operates from a +2.2V to +6.0V source. The device features a low power standby mode which draws less than 1A (maximum). The frequency of the internal oscillator is set with a single external resistor. A single inductor is required to generate the high voltage AC outputs to drive the EL lamps. All input pins are ESD protected with internal diodes to VDD and VSS.
ELEN1 1 ELEN2 2 ROSC 3 no connect 4 no connect 5 no connect 6 VSS 7 SP4480
14 VDD 13 EL2 12 EL1 11 EL3 10 EL4 9 8 CAP COIL
SP4480DS/06
SP4480 Dual 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. Power Supply, VDD.................................................7.0V Input Voltages, Logic.....................-0.3V to (VDD+0.3V) Lamp Outputs...................................................220VP-P Operating Temperature.........................-40C to +85C Storage Temperature..........................-65C to +150C Power Dissipation Per Package 14-pin SOIC (derate 8.33mW/C above +70C)....................700mW 14-pin TSSOP (derate 9.96mW/C above +70C)....................800mW
STORAGE CONSIDERATIONS
Storage in a low humidity environment is preferred. Large high density plastic packages are moisture sensitive and should be stored in Dry Vapor Barrier Bags. Prior to usage, the parts should remain bagged and stored below 40C and 60%RH. If the parts are removed from the bag, they should be used within 48 hours or stored in an environment at or below 20%RH. If the above conditions cannot be followed, the parts should be baked for four hours at 125C in order remove moisture prior to soldering. Sipex ships product in Dry Vapor Barrier Bags with a humidity indicator card and desiccant pack. The humidity indicator should be below 30%RH. The information furnished by Sipex has been carefully reviewed for accuracy and reliability. Its application or use, however, is solely the responsibility of the user. No responsibility of the use of this information become part of the terms and conditions of any subsequent sales agreement with Sipex. Specifications are subject to change without no responsibility for any infringement of patents or other rights of third parties which may result from its use. No license or proprietary rights are granted by implication or otherwise under any patent or patent rights of Sipex Corporation.
SPECIFICATIONS
VDD = +3.0V, L = 470H, CLAMP = 8nF, ROSC = 402k, and TAMB = 25C unless otherwise noted.
PARAMETER Supply Voltage, VDD Supply Current, IDD Shutdown Current, ISD = ICOIL + IDD ELEN Input Voltage, VELEN LOW HIGH Input Resistance ELEN1 and ELEN2 INDUCTOR DRIVE Coil Frequency, fCOIL Coil Duty Cycle Coil Current, ICOIL Peak Coil Current, IPK-COIL EL LAMP OUTPUT EL Lamp Frequency, fLAMP Peak to Peak Output Voltage, VPK-PK
MIN. 2.2
TYP. 3.0 2
MAX. 6.0 4 1
UNITS V mA A LCOIL = 470H VELEN = 0V
CONDITIONS
2.75
0 3.0 1
0.25
V
M
45 40
57
70 73
kHz %
TAMB = +25oC TAMB = -40oC to +85oC
90 39 74 60 100
mA mA Guaranteed by design
350 312 138 130
450
550 570
Hz
TAMB = +25oC TAMB = -40oC to +85oC TAMB = +25oC TAMB = -40oC to +85oC
(c) Copyright 2000 Sipex Corporation
170
V
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SP4480 Dual Electroluminescent Lamp Driver
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PINOUT
ELEN1 1 ELEN2 2 ROSC 3 no connect 4 no connect 5 no connect 6 VSS 7 SP4480
14 VDD 13 EL2 12 EL1 11 EL3 10 EL4 9 8 CAP COIL
PIN ASSIGNMENTS Pin 1 -- ELEN1 -- Electroluminescent Lamp Enable 1. When driven HIGH, this input pin enables the EL driver outputs for EL1 and EL2. This pin has an internal pulldown resistor. Pin 2 -- ELEN2 -- Electroluminescent Lamp Enable 2. When driven HIGH, this input pin enables the EL driver outputs for EL3 and EL4. This pin has an internal pulldown resistor. Pin 3 -- ROSC -- Oscillator Resistor. Connecting a resistor between VDD and this pin sets the frequency of the internal clock. Pin 4 -- No Connect. Pin 5 -- No connect. Pin 6 -- No connect. Pin 7 -- VSS -- Power Supply Ground. Connect to the lowest circuit potential, typically ground. Pin 8 -- COIL -- Coil. The inductor for the boost converter is connected from VBATT to this pin. Pin 9 -- CAP -- Integrating Capacitor. An integrating capacitor connected from this pin to ground filters out any coil switching spikes or ripple present in the output waveform to the EL lamps. Connecting a fast recovery diode from COIL to CAP increases the light output of the EL lamp. Pin 10 -- EL4 -- Electroluminescent Lamp Output 4. This is a high voltage lamp driver output pin paired with EL3 to drive the EL2 lamp. Pin 11 -- EL3 -- Electroluminescent Lamp Output 3. This is a high voltage lamp driver output pin paired with EL4 to drive the EL2 lamp. Pin 12 -- EL1 -- Electroluminescent Lamp Output 1. This is a high voltage lamp driver output pin paired with EL2 to drive the EL1 lamp. Pin 13 -- EL2 -- Electroluminescent Lamp Output 2. This is a high voltage lamp driver output pin paired with EL1 to drive the EL1 lamp. Pin 14 -- VDD -- Positive Power Supply. This pin should be bypassed with a 0.1F capacitor.
(c) Copyright 2000 Sipex Corporation
SP4480DS/06
SP4480 Dual Electroluminescent Lamp Driver
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8
COIL
9
CAP
VDD
14
SP4480
OSC fCOIL
1.8k
SCR1 ROSC 3
SCR2
SCR3
SCR4
fLAMP1 ELEN1 1
fLAMP1 FF7 fLAMP2
ELEN2
2 7
fLAMP2
12
13
11
10
VSS
EL1
EL2
EL3
EL4
Figure 1: Internal Block Diagram of SP4480
DESCRIPTION The SP4480 Dual Electroluminescent Lamp Driver is a low-cost, low voltage device ideal for the replacement of LED backlighting designs in keypads, handsets, PDAs and other portable designs. The EL lamp driver outputs operate in opposite phase so the SP4480 device can be easily implemented into applications driving two EL lamps simultaneously or double-sided EL lamps. Having a dual lamp driver solution on a single IC makes available precious printed circuit board real estate for designers additional circuitry. The SP4480 contains a DC-AC inverter that can produce an AC output of 180VP-P (typical) from a +2.2V to +6.0V input voltage. An internal block diagram of SP4480 can be found in Figure 1. Electroluminescent Technology An EL lamp consists of a thin layer of phosphorous material sandwiched between two strips of plastic which emits light (flouresces) when a high voltage AC signal is applied across it. It
SP4480DS/06
high voltage AC signal is applied across it. It behaves primarily as a capacitive load. Long periods of DC voltage applied to the material tend to reduce its lifetime. With these conditions in mind, the ideal signal to drive an EL lamp is a high voltage sine wave. Traditional approaches to achieve this type of waveform include discrete circuits incorporating a transformer, transistors and several resistors and capacitors. This approach is large and bulky and cannot be implemented in most handheld equipment. Sipex offers low power single chip driver circuits specifically designed to drive small to medium sized electroluminescent panels. Sipex EL drivers provide a differential AC voltage without a DC offset to maximize EL lamp lifetime. The only additional components required for the EL driver circuitry are an inductor, resistor and capacitor. Electroluminescent backlighting is ideal when used with LCD's keypads or other backlit displays. EL lamps uniformly light an area without creating any undesirable "hot spots" in the display. Also, an EL lamp consumes less power that LED's or incandescent bulbs in similar
(c) Copyright 2000 Sipex Corporation
SP4480 Dual Electroluminescent Lamp Driver
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VBATT
ELEN1 ELEN2
1 2 L1 470H
SP4480
VDD ROSC 402k 14 8 COIL D1 1N4148
ROSC
3
9 7
CAP VSS
C1 0.1F
1nF 12 13 EL1 * optional device EL2 11 10 EL3 EL4
CINT 1800pF
EL Lamp
EL Lamp
Figure 2: Typical Application Circuit of the SP4480
lighting situations. These features make EL ideal for attractive, battery powered products. THEORY OF OPERATION Coil Switch The SP4480 has an inductor-based boost converter to generate the high voltage used to drive the EL lamp. Energy is stored in the inductor according to the equation EL = 1/2 (LIpk2) where Ipk = (tON) (VBATT - VCEsat) /L. An internal oscillator controls the coil switch. During the time the coil switch is on, the coil is connected between VDD and the saturation voltage of the coil switch and a magnetic field develops in the coil. When the coil switch turns off, the switch opens, the magnetic field collapses and the voltage across the coil rises. The internal diode forward biases when the coil voltage rises above the H-Bridge voltage and the energy enters the EL lamp. Each pulse increases the voltage across the lamp in discrete steps.
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As the voltage approaches its maximum, the steps become smaller. (see figure 4). The brightness of the EL lamp output is directly related to energy recovery in the boost converter. There are many variations among coils such as magnetic core differences, winding differences and parasitic capacitances. For suggested coil suppliers refer to page 10. Oscillator The internal oscillator generates a high frequency clock used by the boost converter and HBridge. An external resistor from VDD to ROSC sets the oscillator frequency. Typically a 402k resistor sets the frequency to 57kHz. The high frequency clock directly controls the coil switch. This high frequency clock is divided by 128 to generate a low frequency clock which controls the EL H-Bridge and sets the EL lamp frequency. The oscillator has low sensitivity to temperature and supply voltage variations, increasing the performance of the EL
(c) Copyright 2000 Sipex Corporation
SP4480 Dual Electroluminescent Lamp Driver
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driver over the operating parameters. Dual H-Bridge The H-Bridge consists of two SCR structures and two NPN transistors that control how the lamp is charged. Setting ELEN1 to HIGH activates the EL1 and EL2 outputs. Setting ELEN2 to HIGH activates EL3 and EL4 outputs. The EL driver illuminates the lamp by applying the high voltage supply of the boost converter to the lamp terminals through the HBridge and then switching the terminals polarity between the high voltage supply and ground at a constant frequency. This applies an AC voltage to the lamp that is twice the peak output voltage of the boost driver. An AC voltage greater than the 40V across the terminals of the lamp is typically necessary to adequately illuminate the EL lamp. Both EL drivers may be operated simultaneously but with decreased light output from the EL panels. DESIGN CONSIDERATIONS Inductor Selection If limiting peak current draw from the power supply is important, small coil values (<1mH) may need a higher oscillator frequency. Inductor current ramps faster in a lower inductance coil than a higher inductance coil for a given coil switch on time period, resulting in higher peak coil currents. It is important to observe the saturation current rating of a coil. When this current is exceeded, the coil is incapable of storing any more energy and then ceases to act as an inductor. Instead, the coil behaves according to its series DC resistance. Since small coils (<1mH) have inherently low series DC resistance, the current can peak dramatically through a small coil during saturation. This situation results in wasted energy not stored in the magnetics of the coil but expressed as heating which could lead to failure of the coil. Generally, selecting a coil with lower series DC resistance will result in a system with higher efficiency and lamp brightness.
Lamp Effects EL lamp parameters vary between manufacturers. Series DC resistance, lighting efficiency and lamp capacitance per area differ the most overall. Larger lamps require more energy to illuminate. Lowering the oscillator frequency allows more energy to be stored in the coil during each coil switch cycle and increases lamp brightness. The oscillator frequency can be lowered to a point where the lamp brightness then begins to drop because the lamp frequency must be above a critical frequency (approx. 100Hz) to light. Lamp color is affected by the switching frequency of the EL driver. Green EL lamps will emit a more blue light as EL lamp frequency increases. Noise Decoupling on Logic Inputs If ELEN1 or ELEN2 are connected to traces susceptible to noise, it may be necessary to connect bypass capacitors of approximately 10nF between ELEN1 and VSS and ELEN2 and VSS. If these inputs are driven by a microprocessor which provides a low impedance HIGH and LOW signal, then noise bypassing may not be necessary. Increasing Light Output EL lamp light output can be improved by connecting a fast recovery diode from the COIL pin to the CAP pin. The internal diode is bypassed resulting in an increase in light output at the EL lamp. We suggest a fast recovery diode such as the industry standard 1N4148. The optimal value of CINT will vary depending on the lamp parameters and coil value. Lower CINT values can decrease average supply current but higher CINT values can increase lamp brightness. This is best determined by experimentation. A rule of thumb is larger coils (1mH) are paired with a smaller CINT (680pF) and smaller coils (470H) are paired with a larger CINT (1800pF). Changing the EL lamp Output Voltage Waveform Designers can alter the sawtooth output voltage waveform to the EL lamp. Increasing the capacitance of the integration capacitor, CINT, will integrate the sawtooth waveform making it appear more like a square wave.
(c) Copyright 2000 Sipex Corporation
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Printed Circuit Board Layout Suggestions The EL driver's high-frequency operation makes PCB layout important for minimizing electrical noise. Keep the IC's GND pin and the ground leads of C1 and CINT less than 0.2in (5mm) apart. Also keep the connections to the COIL pin as short as possible. To maximize output power and efficiency and minimize output ripple voltage, use a ground plane and solder the IC's VSS pin directly to the ground plane. EL Lamp Driver Design Challenges There are many variables which can be optimized for specific applications. The amount of light emitted is a function of the voltage applied to the lamp, the frequency at which is applied, the lamp material, the lamp size, and the inductor used. Sipex supplies characterization charts to aid the designer in selecting the optimum circuit configuration. Sipex will perform customer application evaluations, using the customer's actual EL lamp to determine the optimum operating conditions for specific applications. For customers considering an EL backlighting solution for the first time, Sipex is able to provide retrofits to nonbacklit products for a thorough electrical and cosmetic evaluation. Please contact your local Sipex sales Representative or the Sipex factory directly to initiate this valuable service.
SP4480DS/06
SP4480 Dual Electroluminescent Lamp Driver
(c) Copyright 2000 Sipex Corporation
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+3V +3V ELEN1 500k ELEN2 ROSC N/C N/C N/C VSS 1 2 3 4 5 6 7 14 13 VDD 0.1F EL2 CEL1 2 7.3nF, 2.5in
12 EL1 EL3 11
1nF
SP4480
10 EL4 9 8 COIL CAP
CEL2 2 7.3nF, 2.5in 1000pF
1N4148 +3V 820H* *DC Resistance 13*
Figure 3: Test Circuit Digram of SP4480
Figure 4: Typical EL Lamp Voltage Waveform
SP4480DS/06
SP4480 Dual Electroluminescent Lamp Driver
(c) Copyright 2000 Sipex Corporation
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PERFORMANCE CHARACTERISTICS
100 90 80
IDD (mA), VCAP,pk (V) Lamp Freq. (Hz)
600 550 500 VCAP,pk 450 400 350 300 250 200 150 100 200 400 600 R OSC (k) 800 1000 200 400 600 R OSC (k) 800 Lumi. Freq.
6.0 5.5 5.0
Luminance (ft-L) Luminance (ft-L)
70 60 50 40 30 20 10 0
4.5 4.0 3.5 3.0 2.5 2.0 1.5 1.0 1000
IDD
Figure 1
Figure 3
140 120
IDD (mA), VCAP,pk (V)
14.0 12.0 10.0
VCAP,pk
IDD (mA), VCAP,pk (V) Luminance (ft-L)
100 80 60 40 20 0 2.0 3.0 4.0 VDD (V) 5.0 6.0
Lumi. IDD
8.0 6.0 4.0 2.0 0.0
100 90 80 70 60 50 40 30 20 10 0
VCAP,pk
Lumi.
10.0 9.0 8.0 7.0 6.0 5.0 4.0 3.0 2.0 1.0 0.0
IDD
400
500
600
700
800
900
1000
H) Inductor Value (
Figure 2
Figure 4
SP4480DS/06
SP4480 Dual Electroluminescent Lamp Driver
(c) Copyright 2000 Sipex Corporation
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Coil Manufacturers
Hitachi Metals Material Trading Division 2101 S. Arlington Heights Road, Suite 116 Arlington Heights, IL 60005-4142 Phone: 1-800-777-8343 Ext. 12 (847) 364-7200 Ext. 12 Fax: (847) 364-7279 Hitachi Metals Ltd. Europe Immernannstrasse 14-16, 40210 Dusseldorf, Germany Contact: Gary Loos Phone: 49-211-16009-0 Fax: 49-211-16009-29 Hitachi Metals Ltd. Kishimoto Bldg. 2-1, Marunouchi 2-chome, Chiyoda-Ku, Tokyo, Japan Contact: Mr. Noboru Abe Phone: 3-3284-4936 Fax: 3-3287-1945 Hitachi Metals Ltd. Singapore 78 Shenton Way #12-01, Singapore 079120 Contact: Mr. Stan Kaiko Phone: 222-8077 Fax: 222-5232 Hitachi Metals Ltd. Hong Kong Room 1107, 11/F., West Wing, Tsim Sha. Tsui Center 66 Mody Road,Tsimshatsui East, Kowloon, Hong Kong Phone: 2724-4188 Fax: 2311-2095 Murata 2200 Lake Park Drive, Smyrna Georgia 30080 U.S.A. Phone: (770) 436-1300 Fax: (770) 436-3030 Murata European Holbeinstrasse 21-23, 90441 Numberg, Postfachanschrift 90015 Phone: 011-4991166870 Fax: 011-49116687225 Murata Taiwan Electronics 225 Chung-Chin Road, Taichung, Taiwan, R.O.C. Phone: 011 88642914151 Fax: 011 88644252929 Murata Electronics Singapore 200 Yishun Ave. 7, Singapore 2776, Republic of Singapore Phone: 011 657584233 Fax: 011 657536181 Murata Hong Kong Room 709-712 Miramar Tower, 1 Kimberly Road, Tsimshatsui, Kowloon, Hong Kong Phone: 011-85223763898 Fax: 011-85223755655 Panasonic. 6550 Katella Ave Cypress, CA 90630-5102 Phone: (714) 373-7366 Fax: (714) 373-7323 Sumida Electric Co., LTD. 5999, New Wilke Road, Suite #110 Rolling Meadows, IL,60008 U.S.A. Phone: (847) 956-0666 Fax: (847) 956-0702 Sumida Electric Co., LTD. 4-8, Kanamachi 2-Chrome, Katsushika-ku, Tokyo 125 Japan Phone: 03-3607-5111 Fax: 03-3607-5144 Sumida Electric Co., LTD. Block 15, 996, Bendemeer Road #04-05 to 06, Singapore 339944 Republic of Singapore Phone: 2963388 Fax: 2963390 Sumida Electric Co., LTD. 14 Floor, Eastern Center, 1065 King's Road, Quarry Bay, Hong Kong Phone: 28806688 Fax: 25659600
Polarizers/transflector Mnfg.
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
SP4480DS/06
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) 448-3452
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
SP4480 Dual Electroluminescent Lamp Driver
(c) Copyright 2000 Sipex Corporation
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PACKAGE: PLASTIC NARROW SMALL OUTLINE (NSOIC)
E
H
D A O e B A1 L
DIMENSIONS in. (mm) Minimum/Maximum A A1 B D E e H L O
14-PIN 0.053/0.069 (1.346/1.748) 0.004/0.010 (0.102/0.249) 0.014/0.018 (0.360/0.460) 0.337/0.344 (8.552/8.748) 0.150/0.157 (3.802/3.988) 0.050 BSC (1.270 BSC) 0.228/0.244 (5.801/6.198) 0.016/0.050 (0.406/1.270) 0/8 (0/8)
SP4480DS/06
SP4480 Dual Electroluminescent Lamp Driver
(c) Copyright 2000 Sipex Corporation
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PACKAGE: PLASTIC THIN SMALL OUTLINE (TSSOP)
E2 E1
D A O e B A1 L
DIMENSIONS in inches (mm) Minimum/Maximum A A1 B D E1 e E2 L O
14-PIN - /0.043 (- /1.10) 0.002/0.006 (0.05/0.15) 0.007/0.012 (0.19/0.30) 0.193/0.201 (4.90/5.10) 0.169/0.177 (4.30/4.50) 0.026 BSC (0.65 BSC) 0.126 BSC (3.20 BSC) 0.020/0.030 (0.50/0.75) 0/8
SP4480DS/06
SP4480 Dual Electroluminescent Lamp Driver
(c) Copyright 2000 Sipex Corporation
12
ORDERING INFORMATION
Model Temperature Range Package Type SP4480EN .............................................. -40C to +85C ....................................... 14-Pin NSOIC SP4480EY .............................................. -40C to +85C ...................................... 14-Pin TSSOP SP4480NEB ........................................................................................................ Evaluation Board
Corporation
SIGNAL PROCESSING EXCELLENCE
Sipex Corporation
Headquarters and Main Offices: 233 South Hillview Drive Milpitas, CA 95035 TEL: (408) 935-7600 FAX: (408) 934-7500 22 Linnell Circle Billerica, MA 01821 TEL: (978) 667-8700 FAX: (978) 670-9001
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.
SP4480DS/06
SP4480 Dual Electroluminescent Lamp Driver
(c) Copyright 2000 Sipex Corporation
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