SP4425Q SIGNAL PROCESSING EXCELLENCE Electroluminescent Lamp Driver for Low Noise Applications ■ Low Noise Waveform ■ Tunable Waveshaping ■ DC to AC Inverter for EL Backlit Display Panels ■ Externally Adjustable Internal Oscillator ■ Low Current Standby Mode APPLICATIONS ■ Cellular Phones ■ Cordless Phones ■ Handsets ■ Backlit LCD Displays DESCRIPTION The SP4425Q is a high voltage output DC-AC converter that can operate from a single 3.0 VDC power supply. The SP4425Q is capable of supplying up to 220 VPP signals, making it ideal for driving electroluminescent lamps. The device features 100 nA (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 select the oscillator and lamp frequencies. The SP4425Q is offered in an 8-pin µSOIC package. For delivery in die form, please consult the factory. 8 HON 7 VDD 3 6 EL1 4 5 EL2 COSC 1 VSS 2 COIL D1 SP4425Q SP4425Q Block Diagram SP4425QDS/12 SP4425Q Electroluminescent Lamp Driver 1 © Copyright 1998 Sipex Corporation ABSOLUTE MAXIMUM RATINGS Power Dissipation Per Package 8-pin µSOIC (derate 4.85mWoC above +70oC)...................390mW 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. 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. VDD.......................................................................................................5V Input Voltages/Currents HON (pin1)........................................-0.5V to (VDD + 0.5V) COIL (pin3)............................................................100mA Lamp Outputs..............................................................................230VPP Storage Temperature....................................................-65˚C to +150˚C SPECIFICATIONS (T= 25°C; VDD = 3.0V; see test circuit schematic page 6; Coil = 2mH/44ohms; COSC = 180pF, CINT = 820pF unless otherwise noted) PARAMETER Supply Voltage, VDD MIN. TYP. MAX. UNITS 2.2 3.0 3.3 V 28 40 mA 3.3 V 0 VDD 0.25V VDD+0.25 V 5 20 µΑ internal pulldown, VHON=VDD=3V 0.1 1.0 µA VHON=0V Supply Current, ICOIL+IDD VDD Coil Voltage, VCOIL HON Input Voltage, VHON LOW: EL off HIGH: EL on -0.25 VDD-0.25 HON Current, EL on Shutdown Current, ISD=ICOIL+IDD CONDITIONS VHON=VDD=3V INDUCTOR DRIVE Coil Frequency, fCOIL=fLAMPx64 Coil Duty Cycle 28.8 kHz 90 % Peak Coil Current, IPK-COIL 90 mA Guaranteed by design. 500 775 Hz TAMB=+25OC, VDD=3.0V TAMB=-40OC to +85OC, VDD=3.0V VPP TAMB=+25OC, VDD=2.2V TAMB=+25OC, VDD=3.0V TAMB=-40OC to +85OC, VDD=3.0V EL LAMP OUTPUT EL Lamp Frequency, fLAMP 300 225 450 Peak to Peak Output Voltage 90 140 90 120 160 This data sheet specifies environmental parameters, final test conditions and limits as well suggested operating conditions. For applications which require performance beyond the specified condition and or limits please consult the factory. Bonding Diagram: VDD HON PAD VDD EL1 EL1 EL2 D1 COIL VSS COSC COSC EL2 Y 427.0 429.0 28.0 -172.0 -381.0 -412.0 -157.5 402.0 HON NOTES: 1. Dimensions are in Microns unless otherwise noted. 2. Bonding pads are 125x125 typ. 3. Outside dimensions are maximum, including scribe area. 4. Die thickness is 380 +/- 25 microns (15 mils +/- 1). 5. Pad center coordinates are relative to die center. 6. Die size 74 x 44 mils. D1 Coil VSS SP4425QDS/12 X 261.0 813.0 813.0 813.0 767.0 143.5 -790.0 -785.5 SP4425Q Electroluminescent Lamp Driver 2 © Copyright 1998 Sipex Corporation PIN DESCRIPTION The SP4425Q 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. For a given choice of coil inductance there will be an optimum COSC capacitor value that provides maximum light output. 8 7 6 5 SP4425Q 1 2 3 4 THEORY OF OPERATION Pin 1 – COSC- Capacitor input 1, connect Capacitor from VSS to Pin 1 to set COSC frequency. The suggested oscillator frequency is 28.8kHz (COSC=180pF). The oscillator output is internally divided to create the control signal for fLAMP. 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, 900kHz, and 450Hz. The oscillator output (28.8kHz) is used to drive the coil (see figure 2 on page 6) 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. Pin 2 – VSS- Power supply common, connect to ground. Pin 3 – Coil- Coil input, connect coil from VDD to pin 3. Pin 4 – D1- Diode Cathode connection. – CINT- Integrator capacitor, connect capacitor from pin 4 to ground to minimize coil glitch energy. Pin 5 – Lamp- Lamp driver output2, connect to EL lamp. Pin 6 – Lamp- Lamp driver output1, 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. The coil is an external component connected from VBATTERY to pin 3 of the SP4425Q. VBATTERY= 3.0 VDC with a 2mH/44Ω coil are typical conditions. Energy is stored in the coil according to the equation VBATTERY 2mH/44Ω VDD Low ESR decoupling capacitor CINT = 820pF typical IN4148 .1µF 7 8 VDD HON 3 4 Coil D1 1MΩ 1 COSC OSC SCR2 SCR1 fCOIL Cap1 180pF fLAMP Q FF1 FF6 Q fLAMP EL2 5 VSS 2 EL1 6 QR2 EL Lamp QR1 SP4425Q Schematic SP4425QDS/12 SP4425Q Electroluminescent Lamp Driver 3 © Copyright 1998 Sipex Corporation EL=1/2LI2, where I is the peak current flowing in the inductor. The current in the inductor is time dependent and is set by the "ON" time of the coil switch: I=(VL/L)tON, where VL is the voltage across the inductor. At the moment the switch closes, the current in the inductor is zero and the entire supply voltage (minus the VSAT of the switch) is across the inductor. The current in the inductor will then ramp up at a linear rate. As the current in the inductor builds up, the voltage across the inductor will decrease due to the resistance of the coil and the "ON" resistance of the switch: VL=VBATTERYIRL-Vsat. Since the voltage across the inductor is decreasing, the current ramp rate also decreases which reduces the current in the coil at the end of tON, the energy stored in the inductor per coil cycle and therefore, the light output. The other important issue is that maximum current (saturation current) in the coil is set by the design and manufacturer of the coil. If the parameters of the application such as VBATTERY, L, RL or tON cause the current in the coil to increase beyond its rated ISAT, excessive heat will be generated and the power efficiency will decrease with no additional light output. 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 28.8kHz oscillator, fLAMP=450Hz. 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 6). A differential view of the outputs is shown in figure 4 on page 6. Layout Considerations The SP4425Q circuit board layout must observe careful analog precautions. For applications with noisy power supply voltages, a 0.1µF low ESR decoupling capacitor must be connected from VDD to ground. Any high voltage traces should be isolated from any digital clock traces or enable lines. A solid ground plane connection is strongly recommended. All traces to the coil or to the high voltage outputs should be kept as short as possible to minimize capacitive coupling to digital clock lines and to reduce EMI emissions. The majority of the current goes through the coil and typically less than 2mA is required for VDD of the SP4425Q. VDD can range from 2.2V to 3.3V; 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 SP4425Q is final tested at 3.0V using a 2mH/44Ω coil from Matsushita. For suggested coil sources see page 10. Integrator Capacitor An integrating capacitor must be placed from pin 4 (D1) to ground in order to minimize glitches associated with switching the coil. A capacitor at this point will collect the high voltage spikes and will maximize the peak to peak voltage output. High resistance EL lamps will produce more pronounced spiking on the EL output waveform; adding the CINT capacitor will minimize the peaking and increase the voltage output at each coil step. The value of the integrator capacitor is application specific. Typical values can range from 500pF to 0.1µF. No integrator capacitor or very small values (500pF) will have a minor effect on the output, whereas a 0.1µF capacitor will cause the output to charge more rapidly creating a square wave output. For most 3V applications an 820 pF integrator capacitor is suitable. 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 (see figure 2 on page 6) 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 6). SP4425QDS/12 SP4425Q Electroluminescent Lamp Driver 4 © Copyright 1998 Sipex Corporation Waveshaping The SP4425Q allows the user to "tune" the output waveform for specific application requirements. External resistors, QR1 and QR2 (see SP4425QCU schematic page 3) can be adjusted to remove any sharp, high frequency edges present on the EL output waveform. Typical values range from 5kΩ to 20kΩ. The waveforms on page 9 show the effect that the Q resistors have on the output. As the sharp discharge edge is filtered, the available noise from the vibration of the lamp is reduced. The user must balance the noise performance with the light output performance to achieve the desired results. 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 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. Both voltage and frequency are directly related to light output. In other words, as the voltage or the frequency of the EL output is increased, the light output will also increase. The voltage has a much larger impact on light output than the frequency does. For example, an output signal of 168VPP with a frequency of 500Hz can yield 15Cd/m2. In the same application a different EL driver could produce 170VPP with a frequency of 450Hz and can also yield 15Cd/m2. Variations in peak-to- peak voltage and variations in lamp frequency are to be expected, light output will also vary from device-to-device however typical light output variations are usually not visually noticeable. 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. SP4425QDS/12 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 7 and 8). SP4425Q Electroluminescent Lamp Driver 5 © Copyright 1998 Sipex Corporation V PEAK =80V (typical) EL1 output; 32 charge steps per half cycle Figure 1. EL1 Output without QR1 and QR2 32 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. EL1, EL2 Output without QR1 and QR2 EL1 Output VPP = 160V (typical) -EL2 Output Differential representation (EL1-EL2) Figure 4. Differential Representation of (EL1 - EL2) without QR1 and QR2 SP4425QDS/12 SP4425Q Electroluminescent Lamp Driver 6 © Copyright 1998 Sipex Corporation 2mH/44Ω Handset Application VIN=3.0V + HON=VDD=ON HON=0V=OFF COSC=180pF – COSC HON VSS VDD Coil EL1 D1 EL2 0.1µF Low ESR Decoupling Capacitor QR1 = 5kΩ EL Lamp IN4148 NOTE: Keep coil as close to SP4425Q as possible QR2 = 5kΩ CINT=820pF SP4425Q 5Ftl 1.5 sq.in. 4nF NOTE: Keep high voltage traces short and away from VDD and clock lines Figure 5. Typical SP4425Q Application Circuit 2mH/44Ω HON=VDD=ON HON=0V=OFF VIN=3V + COSC=180pF – COSC HON VSS VDD Coil EL1 D1 EL2 0.1µF Low ESR Decoupling Capacitor QR1 = 15kΩ 700kΩ IN4148 NOTE: Keep coil as close to SP4425 as possible QR2 = 15kΩ CINT=820pF 3.9nF Test Load SP4425Q NOTE: Keep high voltage traces short and away from VDD and clock lines Figure 6. SP4425Q 3V Test Circuit SP4425QDS/12 SP4425Q Electroluminescent Lamp Driver 7 © Copyright 1998 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. 800 700 600 500 400 300 200 Light Output vs. Temperature 25 Light Output (cd/m2) Lamp Frequency (Hz) Lamp Frequency vs. Temperature 3.0V 2.2V 100 0 -40 0 15 10 5 0 85 70 25 Temperature ( C) 20 -40 0 O 85 O Figure 8. Coil=2mH/44Ω; COSC=180pF; CINT=470pF; VDD=3.0V; Load=3 sq.in. Figure 7. Coil=2mH/44Ω; COSC=180pF; CINT=470pF; CLOAD=4nF Total ICC @3VDD vs. Temperature SP4425 Peak-to-Peak Voltage vs. Temperature 40 35 30 25 20 15 10 5 0 250 Peak- to- Peak Votage (Volts) Total Current (mA) 70 25 Temperature ( C) 200 150 100 3.0V 2.2V 50 -40 0 0 85 70 25 Temperature ( C) -40 O 70 25 Temperature ( C) 85 O Figure 10. Coil=2mH/44Ω; COSC=180pF; CINT=470pF; CLOAD=4nF Figure 9. Coil=2mH/44Ω; COSC=180pF; CINT=470pF; CLOAD=4nF SP4425QDS/12 0 SP4425Q Electroluminescent Lamp Driver 8 © Copyright 1998 Sipex Corporation The following scope photos show the affect the tuning resistors (QR1 and QR2) have on the output waveform. Figure 11 implements only 5KΩ of series resistance introducing only a slight amount of filtering of the discharge edge. Figure 12 shows that if the values are increased to 10KΩ the discharge edge is reduced even further. A 20KΩ example is shown in Figure 14 and represents the most amount of filtering needed. Again, the balance in light output and audible noise must be observed for each application. VBATTERY Coil=Toko 1.2mH/19Ohm CINT=1800pF VDD QR1=5K-20KΩ COSC=270pF SP4425Q EL Lamp QR2=5K-20KΩ Figure 12. QR1=QR2=10KΩ VPP=187VPK-PK, FLAMP=268Hz Low noise suppression level Figure 11. QR1=QR2=5KΩ VPP=196VPK-PK, FLAMP=269Hz Low noise suppression level Figure 14. QR1=QR2=20KΩ VPP=168VPK-PK, FLAMP=266Hz High noise suppression level Figure 13. QR1=QR2=15KΩ VPP=177VPK-PK, FLAMP=269Hz High noise suppression level SP4425QDS/12 SP4425Q Electroluminescent Lamp Driver 9 © Copyright 1998 Sipex Corporation The coil part numbers presented in this data sheet have been qualified as being suitable for the SP4425 product. Contact Sipex for applications assistance in choosing coil values not listed in this data sheet. Coil Manufacturers Coilcraft USA Ph: (847) 639-6400 Fax: (847) 639-1469 Coilcraft Taiwan Ph: 886/2/264-3646 Fax: 886/2/270-0294 Coilcraft Europe Ph: 44 01236 730595 Fax: 44 01236 730627 Coil Craft Singapore Ph: 65 296-6933 Fax: 465 296-4463 #382 New Coils .155 .260 Max 6.60 Coilcraft Hong Kong Ph: 852 770-9428 Fax: 852 770-0729 Dia .115 .175 Max Max Part No. DO1608C-474 470µH, 3.60 ohm (All Dimensions in mm) muRata Taiwan Electronics muRata Hong Kong Ph: 011 88642914151 Ph: 011-85223763898 Fax: 011 88644252929 Fax: 011 852237555655 muRata Europe Ph: 011-4991166870 Fax: 011-49116687225 muRata Electronics Singapore Ph: 011 657584233 Fax: 011 657536181 5.0 ±0.3 5.0 ±0.3 4.7 ±0.3 muRata USA Ph: (770) 436-1300 Fax: (770) 436-3030 Part No. LQN4N471K04 470µH, 11.5 ohm 5.7 ±0.3 (All Dimensions in mm) KOA Speer Electronics, Inc. Ph: 814-362-5536 Fax: 814-362-8883 4.5 ± .02 4.0 ± 0.2 Part No. LPC4045TE471K 470µH, 4.55 ohm 4.5 Max (All Dimensions in mm) Sumida Electric Co., LTD. USA Ph: (847) 956-0666 Fax: (847) 956-0702 Sumida Electric Co., LTD. Singapore Ph: 2963388 Fax: 2963390 Sumida Electric Co., LTD. Japan Ph: 03-3607-5111 Fax: 03-3607-5144 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 470µH, 3.01 ohm (All Dimensions in mm) 5.0 Toko America Inc. USA Ph: (847) 297-0070 Fax: (847) 699-7864 Toko Inc. Japan Ph: 03 3727 1161 Fax: 03 3727 1176 Toko Inc. Hong Kong Ph: 2342-8131 Fax: 2341-9570 Toko Inc. Europe Ph: (0211) 680090 Fax: (0211) 679-9567 Toko Inc. Singapore Ph: (255) 4000 Fax: (250) 8134 Part No. 875FU-122M 1.2mH, 19ohm (All Dimensions in mm) 0.6 + 0.1 2.0 + 0.2 Panasonic Industrial Co., Europe Ph: 44-1344-862-444 Fax: 44-1344-853-706 0.18 + 0.05 Part No. ELT3KN131 2.0mH, 44ohm 1.2+ 0.1 Panasonic Industrial Co., Japan Ph: 81-3-3433-2325 Fax: 81-3-3459-9737 3.3 + 0.2 Panasonic Industrial Co., USA Ph: (201) 348-7000 Fax: (201) 348-0716 (3.1) 5.5 + 0.2 EL polarizers/transflector manufacturers Nitto Denko San Jose, CA Phone: (510) 445-5400 Astra Products Baldwin, NJ Phone: (516) 223-7500 Fax: (516) 868-2371 SP4425QDS/12 0.85 + 0.1 3.3 + 0.1 1.2 + 0.1 (All Dimensions in mm) EL Lamp manufacturers Metro Mark/Leading Edge Minnetonka, MN Phone: (800) 680-5556 Phone: (612) 912-1700 NEC Corporation Tokyo, Japan Phone: (03) 3798-9572 Fax: (03) 3798-6134 Midori Mark Ltd. 1-5 Komagata 2-Chome Taita-Ku 111-0043 Japan Phone: 81-03-3848-2011 Seiko Precision Chiba, Japan Phone: (03) 5610-7089 Fax: (03) 5610-7177 Luminescent Systems Inc. (LSI) Lebanon, NH Phone: (603) 448-3444 Fax: (603) 448-3452 Gunze Electronics 2113 Wells Branch Parkway Austin, TX 78728 Phone: (512) 752-1299 Fax: (512) 252-1181 SP4425Q Electroluminescent Lamp Driver 10 © Copyright 1998 Sipex Corporation All package dimensions in inches 8-pin µSOIC 0.0256 BSC 12.0˚ ±4˚ 0.012 ±0.003 0.008 0.0965 ±0.003 0˚ - 6˚ 0.006 ±0.006 0.006 ±0.006 R .003 SP4425QCU 0.118 ±0.002 0.016 ±0.003 12.0˚ ±4˚ 0.01 0.020 0.020 1 0.0215 ±0.006 0.037 Ref 3.0˚ ±3˚ 2 0.116 ±0.004 0.034 ±0.002 0.116 ±0.004 0.040 ±0.002 0.013 ±0.005 0.118 ±0.002 0.118 ±0.004 0.004 ±0.002 50 SP4425QCU per tube P W µSOIC-8 13" reels: P=8mm, W=12mm Pkg. Minimum qty per reel Standard qty per reel Maximum qty per reel CU 500 2500 3000 SP4425QDS/12 SP4425Q Electroluminescent Lamp Driver 11 © Copyright 1998 Sipex Corporation ORDERING INFORMATION Model Operating Temperature Range Package Type SP4425QCU . ......................................... -40˚C to +85˚C ......................................... 8-Pin µSOIC SP4425QCUEB ................................................ N/A ............................... µSOIC Evaluation Board Please consult the factory for pricing and availability on a Tape-On-Reel option. Corporation SIGNAL PROCESSING EXCELLENCE Sipex Corporation European Sales Offices: Far East: Headquarters and Sales Office 22 Linnell Circle Billerica, MA 01821 TEL: (978) 667-8700 FAX: (978) 670-9001 e-mail: [email protected] ENGLAND: Sipex Corporation 2 Linden House Turk Street Alton Hampshire GU34 IAN England TEL: 44-1420-549527 FAX: 44-1420-542700 e-mail: [email protected] JAPAN: Nippon Sipex Corporation Yahagi No. 2 Building 3-5-3 Uchikanda, Chiyoda-ku Tokyo 101 TEL: 81.3.3256.0577 FAX: 81.3.3256.0621 Sales Office 233 South Hillview Drive Milpitas, CA 95035 TEL: (978) 934-7500 FAX: (978) 935-7600 GERMANY: Sipex GmbH Gautinger Strasse 10 82319 Starnberg TEL: 49.81.51.89810 FAX: 49.81.51.29598 e-mail: [email protected] 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. SP4425QDS/12 SP4425Q Electroluminescent Lamp Driver 12 © Copyright 1998 Sipex Corporation