® SP4414 Low Cost Electroluminescent Lamp Driver ■ Low Power +2.2V to +4.5V Battery Operation ■ Low-Cost EL Driver Ideal for LED Backlighting Replacement ■ DC-to-AC Inverter can Produce Over 160VPP for EL Lamps ■ Requires a 32kHz External Clock Signal ■ Synchronize EL Driver Operation to Existing System Clock for Portable Applications (i.e. Pagers, Cellular Phones, PDAs, etc.) ■ Low Current Standby Mode DESCRIPTION The SP4414 is a high voltage output DC-AC inverter specifically designed to drive electroluminescent lamps to backlight liquid crystal displays, keypads, and backlit readouts used in battery operated portable equipment. The SP4414 will operate from a +2.2V to +4.5 V battery source. The device features a low power shutdown mode which draws less than 100nA (typical), ideal for low power portable products. One external inductor is required to generate the high voltage AC output. An external clock signal is used to drive the internal control signals for the coil and EL lamp. The SP4414 is ideal for portable applications such as pagers, cellular phones, PDAs, and other portable applications using LCDs in dim or low light environments. The SP4414 is offered in 8-pin SOIC and 8-pin µSOIC packages. VBATTERY VDD CLK 1 VSS 2 8 ELEN SP4414 7 L1 2.7mH C1 10nF SP4414 4 7 VDD ELEN EL2 3 6 EL1 COIL 4 5 CINT 8 5 CLK COIL CINT *D1 1N4148 1 6 2 VSS EL1 CINT 100pF 3 EL2 EL Lamp *optional device SP4414DS/17 SP4414 Electroluminescent Lamp Driver 1 © Copyright 2000 Sipex Corporation 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. 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, VBATT.........................................................................7.0V Input Voltages, ELEN (pin 2)....................................-0.5V to (VDD+0.5V) Lamp Outputs...............................................................................200VPP Operating Temperature...................................................-40˚C to +85˚C Storage Temperature.....................................................-65˚C to +150˚C Power Dissipation Per Package 8-pin NSOIC (derate 6.14mW/oC above +70oC)..................................500mW 8-pin µSOIC (derate 4.85mW/oC above +70oC)...................................390mW SPECIFICATIONS VBATT = 3V, L = 2.7mH, CLAMP = 10nF, and CINT = 100pF unless otherwise noted. PARAMETER Supply Voltage, VDD MIN. TYP. MAX. UNITS 2.2 3.0 4.5 V 35 50 mA 4.5 V 0.25V VDD+0.25 V 1 µA Supply Current, ICOIL+IDD Coil Voltage, VCOIL ELEN Input Voltage, VELEN LOW: EL off HIGH: EL on VDD -0.25 VDD-0.25 0 VDD Shutdown Current, ISD=ICOIL+IDD External Oscillator Frequency 32 kHz Coil Frequency, fCOIL=fLAMPx32 8 kHz Coil Duty Cycle 87 % CONDITIONS VELEN=0V, T = 25oC INDUCTOR DRIVE Peak Coil Current, IPK-COIL 60 mA 270 Hz External Oscillator, 50% Duty Cycle. Guaranteed by design. EL LAMP OUTPUT EL Lamp Frequency, fLAMP 230 250 Peak-to-Peak Output Voltage 136 160 SP4414DS/17 VPP SP4414 Electroluminescent Lamp Driver 2 © Copyright 2000 Sipex Corporation PINOUT CLK 1 VSS 2 8 ELEN SP4414 7 VDD EL2 3 6 EL1 COIL 4 5 CINT PIN ASSIGNMENTS Pin 1 — CLK — Clock. Connect this input pin to an external 32KHz clock sets the frequency of the internal flip flops. Pin 5 — C INT — Integrating Capacitor. Connecting a fast recovery diode from COIL (pin 4) to this input pin increases the light output of the EL lamp. An integrating capacitor (100pF) connected from this pin to ground filters out any coil switching spikes or ripple present in the output waveform to the EL lamp. Pin 2 — V SS — Power Supply Common. Connect to the lowest circuit potential, typically ground. Pin 3 — EL2 — Eluminescent Lamp. This is a lamp driver output pin to connect to the EL lamp. Pin 6 — EL1 — Eluminescent Lamp. This is a lamp driver output pin to connect to the EL lamp. Pin 7— VDD — Positive Battery Power Supply. Connect such that +2.2V < VDD < +4.5V. Pin 4 — COIL — Coil. The inductor for the EL lamp is connected from VBATTERY to this input pin. Pin 8 — ELEN — Eluminescent Lamp Enable. When driven HIGH, this input pin enables the EL driver output EL1 and EL2 (pins 6 and 3, respectively) to the EL lamp. SP4414DS/17 SP4414 Electroluminescent Lamp Driver 3 © Copyright 2000 Sipex Corporation DESCRIPTION The SP4414 Electroluminescent Lamp Driver is a low-cost low power device ideal for the replacement of LED backlighting designs. The 32kHz external oscillator drives controls signals for the coil and EL lamp circuitry. The SP4414 32kHz operation is synchronized with existing system clock designs in single cell applications such as pagers, cell phones, PDAs, etc. The SP4414 is built on Sipex's dielectrically isolated BiCMOS process that provides the isolation required to separate the high voltage AC signal used to drive the EL lamp from the low voltage logic and signal processing circuitry. This ensures latch-up free operation in the interface between the low voltage CMOS circuitry and the high voltage bipolar circuitry. The SP4414 contains a DC-AC inverter that can produce an AC output of 180VPP (maximum) from a +2.2V to +4.5V input voltage. An external clock provides the SP4414 with the control signals for the coil and EL lamp. An internal block diagram of the SP4414 can be found in Figure 1. A total of only four external components are required for the standard operation of the SP4414: an inductor, a fast recovery diode, and two capacitors. A diagram of the SP4414 in a typical application can be found in Figure 2. VBATTERY VDD L1 2.7mH 7 SP4414 C1 10nF 4 COIL 5 CINT *D1 1N4148 CINT 100pF SCR2 SCR1 CLK 1 FF1 fCOIL fLAMP Q FF6 Q fLAMP 8 ELEN 6 2 EL1 VSS 3 EL2 EL Lamp * optional device Figure 1. Internal Diagram of the SP4414 SP4414DS/17 SP4414 Electroluminescent Lamp Driver 4 © Copyright 2000 Sipex Corporation Electroluminescent Technology 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 can be difficult to implement in some smaller hand held equipment. Sipex now offers low power single chip driver circuits specifically designed to drive small to medium sized electroluminescent panels. VBATTERY VDD L1 2.7mH SP4414 4 ELEN 8 5 CLK COIL CINT *D1 1N4148 1 6 2 VSS EL1 CINT 100pF 3 EL2 EL Lamp *optional device Figure 2. Typical Application Circuit for the SP4414 down by a flip flop to drive the coil at 8kHz. This signal is divided down by 5 more flip flops to drive the lamp at 250Hz. Market Applications 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 power than LEDs or incandescent bulbs making them ideal for battery powered products. Also, EL lamps are able to evenly light an area without creating any undesirable "hot spots" in the display. The Coil The supply VBATTERY can range from +2.2V to +4.5V. VBATTERY and the coil should be chosen such that ICOIL does not exceed the maximum coil current specification. The majority of the current goes through the coil and is typically much greater than IDD. The coil is an external component connected from VBATTERY to pin 4 of the SP4414. Energy is stored in the coil according to the equation EL=1/2LIP2 where IP, to the first approximation, is the product IP = (tON) (VBATTERY - VCE)/ L), where tON is the time it takes for the coil to reach its peak current, VCE is the voltage drop across the internal NPN transistor for fCOIL, and L is the inductance of the coil. When the NPN transistor switch is off, the energy is forced through a diode which drives the switched H-bridge network. This energy recovery is directly related to the brightness of the EL lamp output. There are many variations among coils; magnetic material differences, winding differences and parasitic capacitances. For suggested coil suppliers, refer to Page 7. THEORY OF OPERATION The SP4414 is a DC-AC inverter made up of: 1. The Frequency Divider, 2. The Coil, and 3. The Switched H-bridge Network. Further details of each element follow. The Oscillator/Frequency Divider The external oscillator provides the SP4414 with a clock signal used to control the coil switch (fCOIL) and the H-bridge network (fLAMP and fLAMP). The ratio of fCOIL/fLAMP will always equal 32 for the SP4414. The external clock frequency is 32kHz. Figure 1 shows the external clock is internally divided SP4414DS/17 7 C1 10nF SP4414 Electroluminescent Lamp Driver 5 © Copyright 2000 Sipex Corporation The fCOIL signal controls a switch that connects the end of the coil at pin 1 to ground or to open circuit. The fCOIL signal is a 87% duty cycle signal switching at the oscillator frequency, 8kHz. 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. When the fCOIL signal is LOW, 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 an array of charge pulses (see Figure 4) 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 3). Printed Circuit Board Layout Suggestions: The SP4414's high-frequency operation makes PC layout important for minimizing ground bounce and noise. Keep the IC's GND pin and the ground leads of C1 and CINT in Figure 2 less than 0.2in (5mm) apart. Also keep the connections to COIL (pin 4) 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 2) 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 by the inductor, the frequency at which it is applied, the lamp material, and the lamp size. Sipex supplies characterization charts to aid the designer in selecting the optimum circuit configuration (see Figures 7 to 9). The Switched H-Bridge Network 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 external oscillator frequency divided by 128. For a 32kHz oscillator, the 7 flip flops will drive fLAMP = 250Hz. 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 offer retrofitted solutions to the customer's existing LED or non-backlit product for a thorough electrical and cosmetic evaluation. Please contact your local Sales Representative for Sipex or the Sipex factory directly to initiate this valued service. 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 32 voltage steps from ground to 80V (typical) on EL1 and EL2 (pins 6 and 3, respectively) which are 180 degrees out of phase (see Figure 5). A differential representation of the output is shown in Figure 6. Fine Tuning Performance Circuit performance of the SP4414 can be improved with some of the following suggestions: Increase EL Lamp Light Output: By connecting a fast recovery diode from COIL (pin 4) to CINT (pin 5), the internal diode of the switched H-bridge network 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, be used for D1. This circuit connection can be found in Figure 2. SP4414DS/17 SP4414 Electroluminescent Lamp Driver 6 © Copyright 2000 Sipex Corporation 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 Toko America Inc. 1250 Feehanville Drive Mt. Prospect, IL, 60056 U.S.A. Phone: (847) 297-0070 Fax: (847) 699-7864 Toko Inc. Europe Burgmullerstr. 7, D-40235 Dusseldorf 1, FR Germany Phone: (0211) 680090 Fax: (0211) 679-9567 Toko Inc. Japan 1-17, Higashi-Yukigaya 2-chome, Ohta-ku, Tokyo 145 Japan Phone: 03-3727-1161 Fax: 03-3727-1176 Toko Inc. Singapore No. 1 Lorong 2. Toa Pavoh. #03-00, Singapore, 319637 Phone: (255) 4000 Fax: (250) 8134 Toko Inc. Hong Kong 45 Hoi Yuen Road, Yau Lee Centre, 7th, 8th, & 9th Fl., Kwun-Tong Kowloon, Hong Kong Phone: 2348131 Fax: 23419570 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 Polarizers/transflector Mnfg. EL Lamp manufacturers Nitto Denko Yoshi Shinozuka Bayside Business Park 48500 Fremont, CA. 94538 Phone: 510 445 5400 Fax: 510 445-5480 Leading Edge Ind. Inc. 11578 Encore Circle Minnetonka, MN 55343 Phone 1-800-845-6992 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 SP4414DS/17 Midori Mark Ltd. 1-5 Komagata 2-Chome Taita-Ku 111-0043 Japan Phone: 81-03-3848-2011 Luminescent Systems Inc. (LSI) 4 Lucent Drive Lebanon, NH. 03766 Phone: (603) 643-7766 Fax: (603) 643-5947 SP4414 Electroluminescent Lamp Driver 7 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 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 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 © Copyright 2000 Sipex Corporation VPEAK=110V (max) EL1 output; 16 charge steps per half cycle Figure 3. EL Output Voltage in Discrete Steps at EL1 Output 16 coil pulses per half cycle; 87% duty cycle. Figure 4. Voltage Pulses Released from the Coil to the EL Driver Circuitry EL1 Output EL2 Output Figure 5. EL Voltage Waveforms from the EL1 and EL2 Outputs EL1 Output VPP=220V (max) EL2 Output Differential Representation E12. Figure 6. EL Differential Output Waveform of the EL1 and EL2 Outputs SP4414DS/17 SP4414 Electroluminescent Lamp Driver 8 © Copyright 2000 Sipex Corporation 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. 35 30 ICC (mA) 25 20 15 10 5 0 1.5 2 2.5 3 3.5 4 5 Lamp Size (sq in) Figure 7. ITOTAL vs Lamp Size Output Voltage (VPP) 250 200 150 100 50 0 1 2 3 4 5 6 7 Lamp Size (sq in) Figure 8. Output Voltage vs Lamp Size SP4414DS/17 SP4414 Electroluminescent Lamp Driver 9 © Copyright 2000 Sipex Corporation Luminance (fL) 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. 4 3.5 3 2.5 2 1.5 1 0.5 0 1 2 3 4 5 6 7 5 6 7 Lamp Size (sq in) Figure 9. Luminance (Foot-Lamberts) vs. Lamp Size Luminance (cd/m 2) 14 12 10 8 6 4 2 > 0 1 2 3 4 Lamp Size (sq in) Figure 10. Luminance (candela per meter square) vs. Lamp Size SP4414DS/17 SP4414 Electroluminescent Lamp Driver 10 © Copyright 2000 Sipex Corporation 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. 12 10 Peak Voltage (V) 8 L=1mH (34 L=2.7mH (44 L=4.8mH (60 6 4 2 0 1 2 3 4 5 6 7 8 9 10 Frequency (kHz) Figure 11. Peak Voltage vs. Frequency 80 70 Supply Current (mA) 60 50 L=1mH (34 L=2.7mH (44 Ohms) L=4.8mH (60 Ohms) 40 30 20 10 0 10 20 30 40 50 60 70 80 90 100 Frequency (kHz) Figure 12. Supply Current vs. Frequency SP4414DS/17 SP4414 Electroluminescent Lamp Driver 11 © Copyright 2000 Sipex Corporation 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. 7.00 6.00 Brightness (fL) 5.00 4.00 L=1mH (34 Ohms) L=2.7mH (44 Ohms) L=4.8mH (60 Ohms) 3.00 2.00 1.00 0.00 10 20 30 40 50 60 70 80 90 100 Frequency (kHz) Figure 13. Brightness vs. Frequency SP4414DS/17 SP4414 Electroluminescent Lamp Driver 12 © Copyright 2000 Sipex Corporation All package dimensions in inches 8-pin µSOIC 8-pin NSOIC 0.0256 BSC 12.0˚ ±4˚ 0.189/0.197 SP4414EN 0.150/0.157 0.228/0.244 0.012 ±0.003 0.053/0.069 0.0965 ±0.003 0.008 0˚ - 6˚ 0.006 ±0.006 0.006 ±0.006 R .003 SP4414EU 0.014/0.019 0.118 ±0.004 0.16 ±0.003 0.050 BSC 1 12.0˚ ±4˚ 0.01 0.020 0.020 1 3.0˚ ±3˚ 0.0215 ±0.006 0.037 Ref 2 0.116 ±0.004 0.034 ±0.004 0.116 ±0.004 0.040 ±0.003 0.013 ±0.005 0.118 ±0.004 0.118 ±0.004 0.004 ±0.002 50 µSOIC devices per tube 95 NSOIC devices per tube, no minimum quantity P W 8-pin NSOIC 13” reels: P = 8mm, W = 12mm 8-pin µSOIC 13” reels: P = 8mm, W = 12mm Pkg. EN EU SP4414DS/17 min qty per reel std qty per reel 500 500 2500 2500 SP4414 Electroluminescent Lamp Driver 13 max qty per reel 3000 3000 © Copyright 2000 Sipex Corporation ORDERING INFORMATION Model Temperature Range Package Type SP4414EN . ............................................ -40˚C to +85˚C ......................................... 8-Pin NSOIC SP4414EU . ............................................ -40˚C to +85˚C ......................................... 8-Pin µSOIC SP4414NEB ..................................................... N/A ........................................... Evaluation Board SP4414UEB ..................................................... N/A ........................................... 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: [email protected] 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. SP4414DS/17 SP4414 Electroluminescent Lamp Driver 14 © Copyright 2000 Sipex Corporation