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(R)
SP4491
Two Panel Electroluminscent Lamp Driver
s Single IC Drives 2 EL Lamps For Backlighting: * Cell Phone Keypad & LCD * Multi-Color EL Lamps * Multi-Segment EL Lamps s Control Over Lamp-A & Lamp-B For Independent Or Concurrent Operation s +2.2V to +6.0V Battery Operation s Single Coil Used To Generate High Voltage AC Outputs s Low Power Standby Mode Draws 100nA Typical Current s A Single Resistor Controls the Internal Oscillator s DC-AC Inverter Produces Up To 220VPP s Space-Saving 10MSOP Package
DESCRIPTION The SP4491 electroluminescent lamp driver provides designers of cell phones PDA's and other handheld, portable electronic devices with an integrated solution for driving two EL lamps independently or concurrently. The SP4491 reduces system cost, component count and board space requirements over a discrete 2-EL driver approach. The EL lamps operate in opposite phase so the SP4491 can be easily implemented in applications driving multi-color or multi-segment EL lamps. The SP4491 operates from a +2.2V to +6.0V battery source. The device features a low power standby mode which draws less than 1A. The frequency of the internal oscillator is set using a single external resistor. A single external 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.
APPLICATIONS s Cellular Phones s PDA's s Handheld GPS Units s Security Systems s POS Terminals
ELEN1 VDD ROSC ELEN2 VSS
1 2 3 4 5 SP4491
10 9 8 7 6
EL1 EL2 ELcommon CAP COIL
Rev. 12/19/00
SP4491 Two Panel Electroluminescent Lamp Driver
(c) Copyright 2000 Sipex Corporation
1
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 10-pin MSOP (derate 8.84mW/C above +70C)....................720mW
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 for 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 other proprietary rights are granted by implication or otherwise under any patent or patent rights of Sipex Corporation.
SPECIFICATIONS
VDD = +3.0V, LCOIL = 2.2mH, ROSC = 560k, El Lamp Load = 4.7nF; CINT = 1000pF and TAMB = 25C unless otherwise noted.
PARAMETER Supply Voltage, VDD Supply Current, IDD Coil Voltage, VCOIL ELEN1/ELEN2 Input Voltage, VELEN LOW HIGH Shutdown Current, ISD=ICOIL+IDD 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.
MAX. 6
UNITS V mA V
CONDITIONS
10 VDD -0.25 VDD-0.25 0 VDD .1
54 9
0.25V VDD+0.25 1
V A
VELEN=0V
36.0 32.0
44.0
55.7 58.2
kHz %
TAMB=+25OC TAMB=-40OC to +85OC TAMB=+25OC
90 9 20 45 90
mA mA
281 250 140
343
435 455 202
Hz V
TAMB=+25OC, VDD=+3.0V TAMB=-40OC to +85OC TAMB=+25OC
Rev. 12/19/00
SP4490 Two Panel Electroluminescent Lamp Driver
(c) Copyright 2000 Sipex Corporation
2
PINOUT
ELEN1 VDD ROSC ELEN2 VSS
1 2 3 4 5 SP4491
10 9 8 7 6
EL1 EL2 ELcommon CAP COIL
PIN ASSIGNMENTS Pin 1 -- ELEN1 -- Electroluminescent Lamp Enable Control Line 1. This is a control line to enable a single or dual EL lamp output. Refer to Table 1 for the control logic. Pin 2 -- VDD -- Positive Battery Power Supply. Connect such that +2.636V < VDD < +3.15V. Pin 3 -- ROSC -- Oscillator Resistor. Connecting a resistor between this input pin andVDD sets the frequency of the internal clock. Pin 4 -- ELEN2 -- Electroluminescent Lamp Enable Control Line 2. This a control line to enable a single or dual EL lamp output. Refer to Table 1 for the control logic. Pin 5 -- VSS -- Power Supply Common. Connect to the lowest circuit potential, typically ground. Pin 6 -- COIL -- Coil. The inductor for the boost converter is connected from VBATT to this input pin. Pin 7 -- CAP -- Integrator Capacitor. An integrating capacitor (1800pF typically) 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 8 -- EL COMMON -- Electroluminescent Common. This is a high voltage lamp driver output pin common to both EL lamps. Pin 9 -- EL2 -- Electroluminescent Lamp Output 2. This is a high voltage lamp driver output pin connect to the second EL lamp. Pin 10 -- EL1 -- Electroluminescent Lamp Output 1. This is a high voltage lamp driver output pin to connect to the first EL lamp.
Rev. 12/19/00 SP4491 Two Panel Electroluminescent Lamp Driver (c) Copyright 2000 Sipex Corporation
3
VBATT
L1 2.2mH 6 COIL D1 1N4148 VBATT VDD 2 9 CAP CINT 1000pF
SP4491
SCR1 SCR2 SCR3 OSC fCOIL
560k
ROSC 3 C2* 1nF
C1 0.1F
fLAMP1
* optional device FF7 fLAMPCOM
ELEN1 ELEN2
1 4
0 1
fLAMP2
5 VSS EL1
10
8 ELcommon
9
EL2
EL Lamp
EL Lamp
Figure 1: Internal Block Diagram of SP4491
ELEN1 0 0 1 1
ELEN2 0 1 0 1
EL1 Output OFF OFF ON ON
EL2 Output OF F ON OF F ON
Table 1: Control Line Logic Table
Rev. 12/19/00
SP4490 Two Panel Electroluminescent Lamp Driver
(c) Copyright 2000 Sipex Corporation
4
DESCRIPTION The SP4491 electroluminescent lamp driver provides designers of cell phones, PDA's and other handheld, portable electronic devices with an integrated solution for driving two EL lamps independently or stimultaneously. The SP4491 reduces system cost, component count and board space requirements over a discrete 2 EL driver approach. The EL lamps operate in opposite phase so the SP4491 can be easily implemented in applications driving multi-color or multi-segment EL lamps. The SP4491 operates from a +2.2V to +6.0V battery source. The device features a low power standby mode that draws less than 1A. The frequency of the internal oscillator is set using a single external resistor. A single external 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. The SP4491 contains a DC-AC inverter that can produce an AC output of 180VPP (typical) from a 3.0V input voltage. An internal block diagram of the SP4491 can be found in Figure 1.
VBATT
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 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.
ELEN1 ELEN2
1 4 L1 470H
SP4491
VDD ROSC 464k 2 6 COIL D1 1N4148
ROSC
3
7 5
CAP VSS
C1 0.1F
C2* 1nF
CINT 1800pF
10 EL1
8 ELcommon
9 EL2
* optional device
EL Lamp
EL Lamp
Figure 2: Typical Application Circuit of SP4491
Rev. 12/19/00
SP4491 Two Panel Electroluminescent Lamp Driver
(c) Copyright 2000 Sipex Corporation
5
Electroluminescent backlighting is ideal when used with LCD displays, keypads or other backlit readouts. EL lamps uniformly light an area without creating any undesirable "hot spots" in the display. Also, an EL lamp typically consumes less power that LED's or incandescent bulbs in similar lighting situations. These features make EL ideal for attractive, battery powered products. THEORY OF OPERATION Coil Switch The SP4491 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. While the coil is connected between VDD and 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 HBridge voltage and the energy enters the EL lamp. Each pulse increases the voltage across the lamp in discrete steps. 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 H-Bridge. And
An external resistor from VDD to ROSC sets the oscillator frequency. Typically a 560k resistor sets the frequency to 44.0kHz. 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 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 ON/OFF to HIGH activates the H-Bridge that is selected by EL1/ EL2. If the EL1/EL2 is low, EL1 is illuminated. If EL1/EL2 is HIGH, EL2 is illuminated. The EL driver illuminates the lamp by applying the high voltage supply of the boost converter to the lamp terminals through the H-Bridge and then switching the terminal 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. Setting ON/OFF to LOW disables the outputs and places the circuit in a low power state. 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.
(c) Copyright 2000 Sipex Corporation
Rev. 12/19/00
SP4490 Two Panel Electroluminescent Lamp Driver
6
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 EL1/EL2 or ON/OFF are connected to traces susceptible to noise, it may be necessary to connect bypass capacitor of approximately 10nF between EL1/EL2 and VSS, and ON/OFF and VSS. If these inputs are driven by a microprocessor which provides a low impedance HIGH and LOW signal, then noise bypassing may not ber 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
Rev. 12/19/00
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. 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 non-backlit 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.
SP4491 Two Panel Electroluminescent Lamp Driver
(c) Copyright 2000 Sipex Corporation
7
0.1uF +3V EL1 1 560K VDD ROSC EL2 10nF 4 2 3 10 9 CEL2 8 7 EL Common CAP
EL1 EL2 CEL1 4.7nf 4.7nf 1000pF
VSS 5
SP4491
6 COIL
1N4148 +3V 2.2mh 28 ohm
Figure 3: Test Circuit Diagram of SP4491
Figure 4: Typical EL Lamp Voltage Waveform
Rev. 12/19/00
SP4490 Two Panel Electroluminescent Lamp Driver
(c) Copyright 2000 Sipex Corporation
8
PERFORMANCE CHARACTERISTICS
Supply Current vs Rosc
50 45 40
20
Luminance vs Rosc
25
Vdd = 3V, L = 470uH
Vdd = 3V, L = 470uH
Supply Current (mA)
35 30 25 20 15 10 5 0 50 150 250 350 450 550 Resistance (kOhm)
Luminance (cd/m2)
15
10
5
0 50 150 250 350 450 550 Resistance (kOhm)
Figure 5
Figure 7
Lamp Frequency vs. Rosc
40 38 36
Output Voltage vs. Rosc
240 230 220
Vdd = 3V, L = 470uH
Vdd = 3V, L = 470uH
32 30 28 26 24 22 20 0.5 1 1.5 2 Lamp Size (in2) 2.5 3 3.5
Output Voltage (V)
34
Frequency (kHz)
210 200 190 180 170 160 150 140 0.5 1 1.5 2 Lamp Size (in2) 2.5 3 3.5
Figure 6
Figure 8
Rev. 12/19/00
SP4491 Two Panel Electroluminescent Lamp Driver
(c) Copyright 2000 Sipex Corporation
9
PERFORMANCE CHARACTERISTICS
Supply Current vs. Lamp Size
40 38 36
Output Voltage vs. Lamp Size
240 230 220
Vdd = 3V, L = 470uH
Vdd = 3V, L = 470uH
Output Voltage (Vp-p)
Supply Current (mA)
34 32 30 28 26 24 22 20 0.5 1 1.5 2 Lamp Size (in2) 2.5 3 3.5
210 200 190 180 170 160 150 140 0.5
1
1.5
2 Lamp Size (in 2 )
2.5
3
3.5
Figure 9
Figure 11
Luminance vs. Lamp Size
Vdd = 3V, L = 470uH
35
Luminance (cd/m2)
30 25 20 15 10 5 0 0.5
1
1.5
2 Lamp Size (in 2 )
2.5
3
3.5
Figure 10
Rev. 12/19/00
SP4490 Two Panel Electroluminescent Lamp Driver
(c) Copyright 2000 Sipex Corporation
10
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
Rev. 12/19/00
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
(c) Copyright 2000 Sipex Corporation
SP4491 Two Panel Electroluminescent Lamp Driver
11
PACKAGE: 10-PIN MSOP PACKAGE
(ALL DIMENSIONS IN MILLIMETERS)
0.50 BSC
0.50 BSC 0.31 0.08
12.0o 3.0
o
2.95 0.10 3.00 0.10
0.30 to 0.07 0.30 to 0.07
0.51 0.13 0.51 0.13 1 2
0.25 0.41 0.08
12.0o 3.0
o
0.55 0.15 0.95BSC
3.0 o 3.0
o
2.95 0.10
0.86 0.08 1.10 MAX 2.95 0.10
0.23 0.07 3.00 0.10 0.10 0.05
3.00 0.10 4.90 0.15
Rev. 12/19/00
SP4490 Two Panel Electroluminescent Lamp Driver
(c) Copyright 2000 Sipex Corporation
12
ORDERING INFORMATION
Model Temperature Range Package Type SP4491EU .............................................. -40C to +85C ........................................ 10-Pin MSOP SP4491UEB ........................................................................................................ Evaluation Board
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 hereing; neither does it convey any license under its patent rights nor the rights of others.
Rev. 12/19/00
SP4491 Two Panel Electroluminescent Lamp Driver
(c) Copyright 2000 Sipex Corporation
13

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