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SP4425Q
SIGNAL PROCESSING EXCELLENCE
Electroluminescent Lamp Driver for Low Noise Applications
s Low Noise Waveform s Tunable Waveshaping s DC to AC Inverter for EL Backlit Display Panels s Externally Adjustable Internal Oscillator s Low Current Standby Mode
APPLICATIONS
s Cellular Phones s Cordless Phones s Handsets s 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 SOIC package. For delivery in die form, please consult the factory.
COSC VSS COIL D1
1 2 3 4 SP4425Q
8 7 6 5
HON VDD EL1 EL2
SP4425Q Block Diagram
SP4425QDS/12 SP4425Q Electroluminescent Lamp Driver (c) Copyright 1998 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. 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 SOIC (derate 4.85mWoC above +70oC)...................390mW
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
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=fLAMPx64 Coil Duty Cycle Peak Coil Current, IPK-COIL EL LAMP OUTPUT EL Lamp Frequency, fLAMP 300 225 90 140 90 450 28.8 90 VDD -0.25 VDD-0.25 0 VDD 5 0.1 MIN. 2.2 TYP. 3.0 28
(T= 25C; VDD = 3.0V; see test circuit schematic page 6; Coil = 2mH/44ohms; COSC = 180pF, CINT = 820pF unless otherwise noted)
MAX. 3.3 40 3.3
UNITS V mA V VHON=VDD=3V
CONDITIONS
0.25V VDD+0.25 20 1.0
V A
internal pulldown, VHON=VDD=3V VHON=0V
kHz % 90 mA Guaranteed by design.
500 775
Hz
TAMB=+25OC, VDD=3.0V TAMB=-40OC to +85OC, VDD=3.0V TAMB=+25OC, VDD=2.2V TAMB=+25OC, VDD=3.0V TAMB=-40OC to +85OC, VDD=3.0V
Peak to Peak Output Voltage
120 160
VPP
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:
HON VDD EL1
PAD
VDD EL1 EL2 D1 COIL VSS COSC
X
261.0 813.0 813.0 813.0 767.0 143.5 -790.0 -785.5
Y
427.0 429.0 28.0 -172.0 -381.0 -412.0 -157.5 402.0
COSC EL2 D1 Coil VSS
SP4425QDS/12
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.
(c) Copyright 1998 Sipex Corporation
SP4425Q Electroluminescent Lamp Driver
2
PIN DESCRIPTION
THEORY OF OPERATION 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. 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. The coil is an external component connected from VBATTERY to pin 3 of the SP4425Q. VBATTERY= 3.0 VDC with a 2mH/44 coil are typical conditions. Energy is stored in the coil according to the equation
1 2 3 4
8 7 6 5
Pin 1 - COSC- Capacitor input 1, connect Capacitor from VSS to Pin 1 to set COSC frequency. 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.
Low ESR decoupling capacitor .1F
VDD 3 Coil
7 VDD 1M 1 COSC OSC Cap1
SP4425Q
VBATTERY
2mH/44 IN4148 8 HON CINT = 820pF typical 4 D1
fCOIL
SCR1
SCR2
180pF fLAMP
Q
FF1
FF6
Q
fLAMP EL2 5 EL1 6 QR2 EL Lamp QR1
VSS 2
SP4425Q Schematic
SP4425QDS/12 SP4425Q Electroluminescent Lamp Driver (c) Copyright 1998 Sipex Corporation
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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 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/44 coil from Matsushita. For suggested coil sources see page 10. 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).
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 0.1F 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. 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 0.1F. No integrator capacitor or very small values (500pF) will have a minor effect on the output, whereas a 0.1F 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.
SP4425QDS/12
SP4425Q Electroluminescent Lamp Driver
(c) Copyright 1998 Sipex Corporation
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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 5k to 20k. 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 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.
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. 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).
SP4425QDS/12
SP4425Q Electroluminescent Lamp Driver
(c) Copyright 1998 Sipex Corporation
5
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 (c) Copyright 1998 Sipex Corporation
6
Handset Application
HON=VDD=ON HON=0V=OFF
2mH/44
VIN=3.0V
+ -
COSC=180pF
COSC VSS Coil D1
HON VDD QR1 = 5k EL1
0.1F Low ESR Decoupling Capacitor
EL Lamp EL2 QR2 = 5k CINT=820pF SP4425Q 1.5 sq.in. 4nF IN4148 NOTE: Keep coil as close to SP4425Q as possible
5Ftl
NOTE: Keep high voltage traces short and away from VDD and clock lines
Figure 5. Typical SP4425Q Application Circuit
HON=VDD=ON HON=0V=OFF
2mH/44
VIN=3V
+ -
COSC=180pF
COSC VSS Coil D1
HON VDD EL1
0.1F Low ESR Decoupling Capacitor QR1 = 15k 700k 3.9nF Test Load
EL2 QR2 = 15k SP4425Q NOTE: Keep high voltage traces short and away from VDD and clock lines
IN4148 NOTE: Keep coil as close to SP4425 as possible
CINT=820pF
Figure 6. SP4425Q 3V Test Circuit
SP4425QDS/12
SP4425Q Electroluminescent Lamp Driver
(c) Copyright 1998 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.
Lamp Frequency vs. Temperature
Lamp Frequency (Hz) Light Output (cd/m2) 800 700 600 500 400 300 200 100 0 -40 0 70 25 Temperature ( C)
O
Light Output vs. Temperature
25 20 15 10 5 0 -40 0 70 25 Temperature ( C)
O
3.0V 2.2V
85
85
Figure 7. Coil=2mH/44; COSC=180pF; CINT=470pF; CLOAD=4nF
Total ICC @3VDD vs. Temperature
40 35 30 25 20 15 10 5 0 -40 0 70 25 Temperature ( C)
O
Figure 8. Coil=2mH/44; COSC=180pF; CINT=470pF; VDD=3.0V; Load=3 sq.in.
SP4425 Peak-to-Peak Voltage vs. Temperature
250 Peak- to- Peak Votage (Volts) 200 150 100 50 85 0 -40 0 70 25 Temperature ( C)
O
Total Current (mA)
3.0V 2.2V
85
Figure 9. Coil=2mH/44; COSC=180pF; CINT=470pF; CLOAD=4nF
Figure 10. Coil=2mH/44; COSC=180pF; CINT=470pF; CLOAD=4nF
SP4425QDS/12
SP4425Q Electroluminescent Lamp Driver
(c) Copyright 1998 Sipex Corporation
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The following scope photos show the affect the tuning resistors (QR1 and QR2) have on the output waveform. Figure 11 implements only 5K of series resistance introducing only a slight amount of filtering of the discharge edge. Figure 12 shows that if the values are increased to 10K the discharge edge is reduced even further. A 20K 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 VDD CINT=1800pF
QR1=5K-20K COSC=270pF SP4425Q
EL Lamp
QR2=5K-20K
Figure 11. QR1=QR2=5K VPP=196VPK-PK, FLAMP=269Hz Low noise suppression level
Figure 12. QR1=QR2=10K VPP=187VPK-PK, FLAMP=268Hz Low noise suppression level
Figure 13. QR1=QR2=15K VPP=177VPK-PK, FLAMP=269Hz High noise suppression level
Figure 14. QR1=QR2=20K VPP=168VPK-PK, FLAMP=266Hz High noise suppression level
SP4425QDS/12
SP4425Q Electroluminescent Lamp Driver
(c) Copyright 1998 Sipex Corporation
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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 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 .02
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 0.2 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
5.0
Toko Inc. Hong Kong Ph: 2342-8131 Fax: 2341-9570 Part No. 875FU-122M 1.2mH, 19ohm
3.3 + 0.1
0.6 + 0.1 3.3 + 0.2 1.2+ 0.1 2.0 + 0.2 0.85 + 0.1
(All Dimensions in mm)
Panasonic Industrial Co., USA Ph: (201) 348-7000 Fax: (201) 348-0716 Panasonic Industrial Co., Europe Ph: 44-1344-862-444 Fax: 44-1344-853-706
Panasonic Industrial Co., Japan Ph: 81-3-3433-2325 Fax: 81-3-3459-9737
Part No. ELT3KN131 2.0mH, 44ohm
(3.1) 5.5 + 0.2
1.2 + 0.1
0.18 + 0.05
(All Dimensions in mm)
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
EL Lamp manufacturers
Metro Mark/Leading Edge Minnetonka, MN Phone: (800) 680-5556 Phone: (612) 912-1700 Midori Mark Ltd. 1-5 Komagata 2-Chome Taita-Ku 111-0043 Japan Phone: 81-03-3848-2011 Luminescent Systems Inc. (LSI) Lebanon, NH Phone: (603) 448-3444 Fax: (603) 448-3452 NEC Corporation Tokyo, Japan Phone: (03) 3798-9572 Fax: (03) 3798-6134 Seiko Precision Chiba, 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 1998 Sipex Corporation
SP4425QDS/12
SP4425Q Electroluminescent Lamp Driver
10
All package dimensions in inches 8-pin SOIC
0.0256 BSC 0.012 0.003 0.0965 0.003 R .003 12.0 4 0.008 0 - 6 0.006 0.006 0.006 0.006
SP4425QCU
0.118 0.002
0.016 0.003 12.0 4 0.01
0.020 0.020 1 2
0.0215 0.006 0.037 Ref
3.0 3
0.116 0.004
0.034 0.002 0.040 0.002 0.116 0.004
0.013 0.005 0.118 0.002
0.004 0.002
0.118 0.004
50 SP4425QCU per tube
P
W
SOIC-8 13" reels: P=8mm, W=12mm Pkg. CU Minimum qty per reel 500 Standard qty per reel 2500 Maximum qty per reel 3000
SP4425QDS/12
SP4425Q Electroluminescent Lamp Driver
(c) Copyright 1998 Sipex Corporation
11
ORDERING INFORMATION
Model Operating Temperature Range Package Type SP4425QCU . ......................................... -40C to +85C ......................................... 8-Pin SOIC SP4425QCUEB ................................................ N/A ............................... SOIC 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: (978) 934-7500 FAX: (978) 935-7600 European Sales Offices: ENGLAND: Sipex Corporation 2 Linden House Turk Street Alton Hampshire GU34 IAN England TEL: 44-1420-549527 FAX: 44-1420-542700 e-mail: mikeb@sipex.co.uk Far East: 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
GERMANY: Sipex GmbH Gautinger Strasse 10 82319 Starnberg TEL: 49.81.51.89810 FAX: 49.81.51.29598 e-mail: sipex-starnberg@t-online.de
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
(c) Copyright 1998 Sipex Corporation
12

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