ZXSC100 SINGLE CELL DC-DC CONVERTER SOLUTION DESCRIPTION efficiency over a wider range of load currents, several circuit configurations are possible with power dissipation up to 2W. The step up output voltage is easily programmed with external resistors, the non-synchronous architecture and SuperSOT4™ device enabling an output voltage down to the input voltage level. For best performance the ZXSC100 quiescent current is a small 150µA ensuring minimum battery drain in no load conditions. The ZXSC100 series is designed for DC-DC applications where step-up voltage conversion from very low input voltages is required. These applications mainly operate from single nickel cadmium or nickel metal hydride battery cells. The ZXSC100 devices are non-synchronous PFM, DC-DC controller ICs which drive an external transistor. Zetex SuperSOT4™ switching transistors, with saturation resistance as low as 13mΩ, are recommended as the external switching element. These bipolar transistors are the best switching devices available for this type of DC-DC conversion, enabling high efficiency conversion with input voltages down to below 1 volt. For the best in space saving the ZXSC100 is offered in the MSOP8 package, however the devices are also available in SO8 packaging for applications where space saving is not so critical. The IC and discrete combination offers the ultimate cost vs performance solution for single cell DC-DC conversion. The circuit can start up under full load with regulation maintained down to an input voltage of only 0.926 volts. The solution configuration ensures optimum FEATURES APPLICATIONS(continued) • SuperSOT4™ switching transistor ZXT14N20DX:VCE(sat) 45mV max @ 1A load • Efficiency maintained over a wide range of input voltages and load currents 82% efficiency @ VBATT=1V • • • • • • Startup under full load • Minimum operating input voltage VBATT=0.926V • Adjustable output voltage down to VBATT • Quiescent current typically 150µA referred to input voltage • MSOP8 Package • SO8 Package • Demonstration boards available Hand Held Instruments Portable Medical Equipment Solar Powered Equipment LED Flashlight LED Backlight TYPICAL APPLICATION CIRCUIT L1 VBATT 3.3V/0.1A R1 Q1 Cordless Telephones MP3 Players PDA Pagers Battery Backup Supplies Electronic toothbrush GPS Receivers Digital Camera Palmtop Computers EM VDRIVE BAS ISENSE RE FB VCC GND ZXSC100 C1 ISSUE 1 - JANUARY 2001 1 R3 ZXT14N20DX U1 APPLICATIONS • • • • • • • • • D1 ZHCS2000 C3 C2 R2 R4 ZXSC100 ABSOLUTE MAXIMUM RATING Supply Voltage Maximum Voltage Other Pins Power Dissipation MSOP8 SO8 Operating Temperature Storage Temperature Junction Temperature 0.3 to 3.5V 0.3 to VCC+0.3V 0 to 70°C -55 to 125°C 150°C 500mW 780mW ELECTRICAL CHARACTERISTICS TEST CONDITIONS (Unless otherwise stated) VCC=1.2V, TA = 25°C Symbol Parameter Conditions Min Typ Max Units I CC Quiescent current Not switching I DRIVE Base drive current V RE = V CC 5 V DRIVE V DRIVE o/p voltage V RE = V CC , I DRIVE = 5mA V CC - 0.17 V FB Feedback voltage 708 730 752 mV V ISENSE Output current reference voltage 12 17.5 24 mV T CVISENSE I SENSE voltage temp co. V DREF Drive current reference voltage T CVDREF V DREF temp co. V CC(SRT) Startup voltage V CC(min) Minimum operating input voltage V CC(hys) Supply start up to shutdown hysteresis 80 I FB Feedback input current 100 200 nA I ISENSE I SENSE input current 4 5.5 µA V O(min) Minimum Output Voltage V O(max) Maximum Output Voltage 1 150 200 µA 10 mA V 0.4 Measured with respect to V CC 20 30 %/°C 40 1 Any output load V ISENSE = 0V mV %/°C 1.01 1.06 1.1 V 0.926 0.98 1 V 3 mV V CC V ZXT14N20DX as pass element 1 20 V Depends on breakdown voltage of pass device. See ZXT14N20DX data sheet ISSUE 1 - JANUARY 2001 2 ZXSC100 ELECTRICAL CHARACTERISTICS: AC PARAMETERS2 TEST CONDITIONS (Unless otherwise stated) ) VCC=1.2V, TA = 25°C Symbol 2 3 Parameter T OFF Discharge Pulse Width F OSC Recommended operating frequency 3 Conditions Min Typ 1.7 3 Max Units 4 µs 200 kHz These parameters guaranteed by Design Operating frequency is application circuit dependant. See applications section ZXT14N20DX For the circuits described in the applications section, Zetex ZXT14N20DX is the recommended pass transistor. The following indicates outline data for the ZXT, more detailed information can be found in the Zetex SuperSOT4 data book or at www.zetex.com ELECTRICAL CHARACTERISTICS (at TA = 25°C unless otherwise stated). PARAMETER SYMBOL MIN. TYP. Collector-Emitter Breakdown Voltage V (BR)CEO 20 30 Collector-Emitter Saturation Voltage V CE(sat) MAX. 4.5 30 75 6 45 95 UNIT CONDITIONS. V I C =10mA* mV mV mV I C =0.1A, I B =10mA* I C =1A, I B =10mA* I C =4A, I B =40mA* *Measured under pulsed conditions. Pulse width=300µs. Duty cycle ≤2% ZHCS2000 For the circuits described in the applications section Zetex ZHCS2000 is the recommended Schottky diode. The following indicates outline data for the ZHCS, more detailed information is available at www.zetex.com ELECTRICAL CHARACTERISTICS (at Tamb = 25°C unless otherwise stated). PARAMETER SYMBOL Forward Voltage MIN. TYP. MAX. UNIT CONDITIONS. VF 385 500 mV mV I F =1A I F =2A Reverse Current IR 300 µA V R =30V Reverse Recovery Time t rr ns Switched from IF = 500mA to IR = 500mA. Measured at IR=50mA 5.5 *Measured under pulsed conditions. Pulse width=300µs. Duty cycle ≤ 2% ISSUE 1 - JANUARY 2001 3 ZXSC100 TYPICAL CHARACTERISTICS ISSUE 1 - JANUARY 2001 4 ZXSC100 DEVICE DESCRIPTION The driver circuit supplies the external switching transistor with a defined current, which is programmed by an external resistor connected between the RE pin and VCC. The internal reference voltage for the circuit is 25mV below VCC. To maximise efficiency the external transistor is switched quickly, typically being forced off within 20ns. The ZXSC100 is non-synchronous PFM, DC-DC controller IC which, when combined with a high performance external transistor, enables the production of a high efficiency boost converter for use in single cell applications. A block diagram is shown for the ZXSC100 in Figure 1. In higher power applications more current can be supplied to the switching transistor by using a further external component. The driver transistor in the IC can be bypassed with the addition of a discrete PNP. More information on this circuit configuration can be found in the applications section. Figure 1 ZXSC100 Block Diagram A shutdown circuit turns the device on or off at VCC=1V with a hysteresis of typically 80mV. At start up, comparator Comp1 turns the driver circuit and therefore the external switching transistor on. This circuit will remain active until the feedback voltage at the pin FB rises above VREF, which is set to 730mV. An external resistive divider on the FB pin sets the output voltage level. Comparator Comp2 forces the driver circuit and the external switching transistor off, if the voltage at ISENSE exceeds 25mV. The voltage at ISENSE is taken from a current sense resistor connected in series with the emitter of the switching transistor. A monostable following the output of Comp2 extends the turn-off time of the output stage by a minimum of 2us. This ensures that there is sufficient time to discharge the inductor coil before the next on period. The AND gate between the monostable and Comp1 output ensures that the switching transistor always remains on until the ISENSE threshold is reached and that the minimum discharge period is always asserted. The pulse width is constant, the pulse frequency varies with the output load. ISSUE 1 - JANUARY 2001 5 ZXSC100 PIN DESCRIPTIONS Pin No. Name Description 1 EM Emitter of internal drive transistor. Connect to RE in lower power applications. Must be unconnected in higher power applications 2 BAS Not connected in lower power applications. Connect to base of external drive transistor in higher power applications 3 RE Drive current sense input. Internal threshold voltage set 25mV below V CC . Connected external sense resistor. Connect emitter of external drive transistor in higher power applications 4 V CC Supply voltage, generally NiMH, NiCd single cell 5 I SENSE Inductor current sense input. Internal threshold voltage set to 25mV. Connect external sense resistor 6 FB Feedback sense. Internal threshold set to 730mV. Connect external resistive divider to output voltage 7 G ND Ground 8 V DRIVE Drive output for external switching transistor. Connect to base of external switching transistor. Also connect to collector of external drive transistor in higher power applications VDRIVE GND EM 1 8 BAS 2 7 RE 3 6 FB VCC 4 5 ISENSE REFERENCE DESIGNS output power of 1.0W and finally driving white LED’s in a flashlight application. Three typical DC-DC step-up converter applications for the ZXSC100 are shown. Firstly with a maximum output power of 0.33W, secondly with a maximum Low Power Solution (330mW) Efficiency ISSUE 1 - JANUARY 2001 6 ZXSC100 Low power solution, VOUT=3.3V, PL=0.33W L1 VBATT D1 3.3V/0.1A ZHCS2000 R1 Q1 R3 ZXT14N20DX U1 EM VDRIVE BAS ISENSE RE FB VCC GND ZXSC100 C1 C3 C2 R2 R4 Materials list Ref Value Part Number Manufacturer Comments U1 N/A ZXSC100X8 Zetex Plc Single cell converter, MSOP8 Q1 20V, 13mΩ, 7A ZXT14N20DX Zetex Plc Low VCE(sat) NPN, MSOP8 D1 0.5V, 2A ZHCS2000 Zetex Plc 2A Shottky diode R1 0Ω* Generic Various 0805 Size R2 33mΩ Generic Various 0805 Size R3 110kΩ Generic Various 0805 Size R4 30kΩ Generic Various 0805 Size C1 220µF TPSD227M010R0100 AVX Low ESR tantalum capacitor C2 220µF TPSD227M010R0100 AVX Low ESR tantalum capacitor C3 1nF Generic Various 0805 Size L1 22µH D01608C-223 D03316P-223 Coilcraft Low profile SMT * Note: Refer to External Transistor base drive selection in the Applications Section. ISSUE 1 - JANUARY 2001 7 ZXSC100 Higher power solution, VOUT=3.3V, PL=1W L1 VBATT D1 3.3V/0.33A ZHCS2000 R1 Q2 Q1 R3 C3 ZXT14N20DX U1 EM VDRIVE BAS ISENSE RE FB VCC GND C2 ZXSC100 R2 C1 R4 Materials list Ref Value Part Number Manufacturer Comments U1 N/A ZXSC100X8 Zetex Plc Single cell converter, MSOP8 Q1 20V, 13mΩ, 7A ZXT14N20DX Zetex Plc Low VCE(SAT) NPN, MSOP8 Q2 N/A 2N2907 Various Small signal transistor D1 0.5V, 2A ZHCS2000 Zetex Plc 2A Shottky diode R1 3.3Ω* Generic Various 0805 Size R2 33mΩ Generic Various 0805 Size R3 110kΩ Generic Various 0805 Size R4 30kΩ Generic Various 0805 Size C1 220µF TPSD227M010R0100 AVX Low ESR tantalum capacitor C2 220µF TPSD227M010R0100 AVX Low ESR tantalum capacitor C3 1nF Generic Various 0805 Size L1 22µH D01608C-223 D03316P-223 Coilcraft Low profile SMT * Note: Refer to External Transistor base drive selection in the Applications Section. ISSUE 1 - JANUARY 2001 8 ZXSC100 ZXSC uses the very small MSOP8 package, the pass transistor is SOT23. No capacitors are required as the circuit is stable under all conditions. The inductor recommended is a low cost miniature component. OTHER APPLICATIONS Driving white LED’s in a flashlight application No compromise is made on efficiency however. In a standard configuration efficiency well over 80% can be achieved. With careful inductor selection efficiency over 90% is possible. L1 VBATT 100µH Q1 ZXT13N15 U1 EM VDRIVE BAS ISENSE RE FB VCC GND D1 The inherent flexibility of the ZXSC circuit means that parallel or series LEDs can be driven depending on application needs. A simple modification to the application circuit means that the maximum pulse current can be programmed to match the characteristics of the chosen LED load, pulse current in the range 10mA to 3A and beyond can be easily achieved. WHITE LED R2 0.22R ZXSC100 The ZXSC100 solution is ideal for LED lamp driving applications operating from a single cell. In principal conversion from 1.2V to the 3.6V, typically required by white LEDs, is necessary. Load currents in the region of 20mA to 50mA being required for a single LED element. To minimise size, weight and cost, single cell operation is an advantage. The ZXSC is well matched to single cell NiCd and NiMH characteristics. The circuit will turn on at 1.06V, to maximise the life the battery can offer, the converter does not turn off until the battery voltage falls to 0.93V. The circuit itself is very simple, a minimum number of components are used and they are all small size. The ISSUE 1 - JANUARY 2001 9 An application note (AN33) is available describing various circuits for driving white LEDs. This application note includes details of circuits that optimise battery life, maximise brightness and can be constructed for minimal cost. Contact your local Zetex office for further details. ZXSC100 APPLICATIONS INFORMATION The following section is a design guide for optimum converter performance. Switching transistor selection The choice of switching transistor has a major impact on the DC-DC converter efficiency. For optimum performance, a bipolar transistor with low VCE(SAT) and high gain is required. The majority of losses in the transistor are, ‘on-state’ and can be calculated by using the formula below: PQ1 = ((IAVxVCE(SAT) ) + ( IBx VBE(SAT) ))xTON (TON + TOFF) ) where IAV = I PK 2 ZXT14N20DX Saturation Characteristic. External drive transistor selection From the calculations above the impact on converter efficiency can be seen. For higher power applications an external transistor is required to provide the additional base drive current to the main switching transistor. For this, any small signal PNP transistor is sufficient. Please see reference designs for recommended part numbers. The Zetex ZXT14N20DX is an ideal choice of transistor, having the lowest saturation voltage in its class. A data sheet for the ZXT14N20DX is available on the Zetex web site or through your local Zetex sales office. Outline information is included in the characteristics section of this data sheet. Schottky diode selection As with the switching transistor the Schottky rectifier diode has a major impact on the DC-DC converter efficiency. A Schottky diode with a low forward voltage and fast recovery time should be used for this application. The majority of losses in the diode are, ‘on-state’ and can be calculated by using the formula below: PD1 = IAV x VF(MAX) x TDIS (TOn + TOFF ) where IAV = I PK 2 The diode should be selected so that the maximum forward current is greater or equal to the maximum peak current in the inductor, and the maximum reverse voltage is greater or equal to the output voltage. ZXT14N20DX Saturation Characteristic. The Zetex ZHCS2000 meets these needs. A data sheet for the ZHCS2000 is available on the Zetex web site or through your local Zetex sales office. Outline information is included in the characteristics section of this data sheet. ISSUE 1 - JANUARY 2001 10 ZXSC100 Figure 3 shows the discontinuous inductor current and the relationship between output power, TON, TDIS and TOFF. Inductor selection The inductor value must be chosen to satisfy performance, cost and size requirements of the overall solution. For the reference designs we recommend an inductor value of 22µH with a core saturation current rating greater than the converter peak current value. Inductor selection has a significant impact on the converter efficiency. For applications where efficiency is critical, a 5% improvement can be achieved with a high performance inductor. This should be selected with a core saturation current rating much higher than the peak current of the converter, say 3 times greater. The resultant reduction in core losses brings about the efficiency improvement. Peak current definition Figure 3 Discontinuous inductor current The peak current rating is a design parameter whose value is dependent upon the overall application. For the reference designs, a peak current of 1.2A was chosen to ensure that the converter could provide the required output power. Output capacitors Output capacitors are a critical choice in the overall performance of the solution. They are required to filter the output and supply load transient currents. There are three parameters which are paramount in the selection of the output capacitors; their capacitance value, IRIPPLE and ESR. The capacitance value is selected to meet the load transient requirements. The capacitors IRIPPLE rating must meet or exceed the current ripple of the solution. In general, the IPK value must be chosen to ensure that the switching transistor, Q1, is in full saturation with maximum output power conditions, assuming worse-case input voltage and transistor gain under all operating temperature extremes. Once IPK is decided the value of RSENSE can be determined by: RSENSE = VISENSE IPK The ESR of the output capacitor can also affect loop stability and transient performance. The capacitors selected for the solution, and indicated in the reference designs, are optimised to provide the best overall performance. Output power definition By making the above assumptions for the inductor and IPK the output power can be determined by: Output Power = (VOUT − VIN) x IPK x TDIS 2 x (TOn + TOFF ) where TON = IPK xL VIN and TDIS = IPK xL (VOUT − VIN) Note: VOUT = output voltage + rectifier diode VF ISSUE 1 - JANUARY 2001 11 ZXSC100 Input capacitors VOUT The input capacitor is chosen for its voltage and RMS current rating. The use of low ESR electrolytic or tantalum capacitors is recommended. Capacitor values for optimum performance are suggested in the reference design section. RA Also note that the ESR of the input capacitor is effectively in series with the input and hence contributes to efficiency losses in the order of IRMS2 x ESR. VFB Output voltage adjustment RB The ZXSC100 is an adjustable converter allowing the end user the maximum flexibility in output voltage selection. For adjustable operation a potential divider network is connected as indicated in the diagram. 0V The output voltage is determined by the equation: External Transistor base drive selection VOUT= VFB (1 + RA / RB), Optimisation of the external switching transistor base drive may be necessary for improved efficiency in low power applications. This can be achieved by introducing an external resistor between the supply and the RE pin of the ZXSC100. The resistor value can be determined by: where VFB=730mV The resistor values, RA and RB, should be maximised to improve efficiency and decrease battery drain. Optimisation can be achieved by providing a minimum current of IFB(MAX)=200nA to the VBATT pin. The output is adjustable from VFB to the (BR)VCEO of the switching transistor, Q1. R1 = VDREF IB Note: For the reference designs, RA is assigned the label R3 and RB the label R4. ISSUE 1 - JANUARY 2001 12 ZXSC100 minimising parasitic inductance, capacitance and resistance. Also the sense resistor R2 should be connected, with minimum trace length, between emitter lead of Q1 and ground, again minimising stray parasitics. Layout issues Layout is critical for the circuit to function optimally in terms of electrical efficiency, thermal considerations and noise. For ‘step-up converters’ there are four main current loops, the input loop, power-switch loop, rectifier loop and output loop. The supply charging the input capacitor forms the input loop. The power-switch loop is defined when Q1 is ‘on’, current flows from the input through the inductor, Q1, RSENSE and to ground. When Q1 is ‘off’, the energy stored in the inductor is transferred to the output capacitor and load via D1, forming the rectifier loop. The output loop is formed by the output capacitor supplying the load when Q1 is switched back off. The layout for the 0.33W solution is shown below. Demonstration board A demonstration board for the 0.33W solution, is available upon request. These can be obtained through your local Zetex office or through Zetex web pages. For all reference designs, Gerber files and bill of materials can be supplied. Actual Size To optimise for best performance each of these loops should be kept separate from each other and interconnections made with short, thick traces thus Top Silk Drill Holes Top Copper Bottom Copper 0.33W solution demo board layout ISSUE 1 - JANUARY 2001 13 ZXSC100 Designing with the ZXSC100. Main switching waveforms Introduction Steady state operation under constant load gives an excellent indication of ZXSC100 performance. Represented in Figure 3. is the main switching waveform, measured at the collector of Q1, indicating the transistor on-state and the diode energy transfer to the output. This section refers to the ZXSC100, 3.3V/100mA output reference design and demonstrates the dynamic performance of the solution. Figure 1. ZXSC100 low power solution, 3.3V/100mA output. Efficiency Figure 3. Switching waveform The peak switching current is derived from the threshold of the ISENSE pin and the sense resistor value (see Applications section for calculations). Figure 4. shows the switching waveform associated with the ISENSE pin Efficiency is often quoted as one of the key parameters of a DC-DC converter. Not only does it give an instantaneous idea of heat dissipation, but also an idea as to the extent battery life can be extended. Figure 2. Shows the efficiency of the ZXSC100 low power solution. Efficiency v Output current is shown for a 3.3V output at various input voltages. Figure 2. ZXSC100 efficiency v output current Figure 4. ISENSE threshold ISSUE 1 - JANUARY 2001 14 ZXSC100 Shown in Figure 5. is the discontinuous inductor current. The ramp-up current stores energy in the inductor. The switching transistor,Q1, is on during this time and has an equivalent current ramp-up, shown in Figure 6. The ramp-down current is associated with the energy being delivered to the output via the Schottky diode, D1. The diode current is equivalent to this ramp-down current and is shown in figure 7. Figure 7. Diode current (200mA/div) Figure 5. Inductor current (200mA/div) Figure 6. Transistor current (200mA/div) ISSUE 1 - JANUARY 2001 15 ZXSC100 Output Voltage Ripple Output voltage ripple is shown in Figure 8. The circuit is operated with a 1.2V input voltage, 3.3V output voltage and 100mA load current. Output voltage ripple will be dependent, to a large extent, on the output capacitor ESR. (see Applications section for recommended capacitors). Figure 8. Output voltage ripple for 3.3V/100mA output. Transient response Transient response to step changes in load is a critical feature in many converter circuits. The ZXSC100 operates a pulse by pulse regulation scheme and therefore corrects for changes in the output every pulse cycle, giving excellent response characteristic. Measurement with a power supply When measuring with a power supply it is important to realise that the impedance is much greater than that of a secondary battery (NiCd or NiMH). To simulate the lower impedance of the battery x10 low ESR 1000uF capacitors where placed in parallel at the input of the c o n v e r te r . A l l th e dy nam i c pe rf orm anc e measurements were taken using this technique. ISSUE 1 - JANUARY 2001 16 ZXSC100 Supplier Listing Zetex GERMANY Zetex GmbH Munich ASIA Zetex Asia Hong Kong USA Zetex Inc Long Island NY UK Zetex PLC Chadderton, Oldham (49) 894549490 (852) 2610 0611 (1) 631 543 7100 (44) 161 622 4444 AVX USA (1) 843 448 9411 AVX UK (44) 1252 770000 Coilcraft Inc (1) 847 639 6400 Coilcraft Europe (44) 1236 730595 SANYO Electronics Ltd. Forrest City, AR 870 633 5030 San Diego, CA 619 661 6835 Rochelle Pk, NJ 201 843 8100 Semicon UK Ltd (44) 1279 422224 http://www.zetex.com AVX Asia Singapore (65) 258 2833 AVX http://www.avxcorp.com Coilcraft http://www.coilcraft.com San y o E l e c t r o n i c Sanyo Europe Munich Comp. (OS-CON) (49) 89 457693 16 SANYO Electronics Ltd. Hong Kong (852) 21936888 Singapore (65) 281 3226 Japan (81) 720 70 6306 http://www.sanyovideo.com ISSUE 1 - JANUARY 2001 17 ZXSC100 CONNECTION DIAGRAMS VDRIVE GND EM 1 8 BAS 2 7 RE 3 6 FB VCC 4 5 ISENSE MSOP8 DIM Millimetres Inches MIN MAX MIN MAX A 0.91 1.11 0.036 0.044 A1 0.10 0.20 0.004 0.008 B 0.25 0.36 0.010 0.014 C 0.13 0.18 0.005 0.007 D 2.95 3.05 0.116 0.120 e 0.65 NOM 0.0256 NOM e1 0.33 NOM 0.0128 NOM E 2.95 3.05 0.116 0.120 H 4.78 5.03 0.188 0.198 L 0.41 0.66 0.016 0.026 θ° 0° 6° 0° 6° SO8 DIM Millimetres Inches Min Max Min Max A 4.80 4.98 0.189 0.196 B 1.27 BSC 0.05 BSC C 0.53 REF 0.02 REF D 0.36 0.46 0.014 0.018 E 3.81 3.99 0.15 0.157 F 1.35 1.75 0.05 0.07 G 0.10 0.25 0.004 0.010 J 5.80 6.20 0.23 0.24 K 0° 8° 0° 8° L 0.41 1.27 0.016 0.050 ISSUE 1 - JANUARY 2001 18 ZXSC100 ORDERING INFORMATION DEVICE Package Partmarking ZXSC100X8 MSOP8 ZXSC100 ZXSC100N8 SO8 ZXSC100 Zetex plc. Fields New Road, Chadderton, Oldham, OL9-8NP, United Kingdom. Telephone: (44)161 622 4422 (Sales), (44)161 622 4444 (General Enquiries) Fax: (44)161 622 4420 Zetex GmbH Streitfeldstraße 19 D-81673 München Germany Telefon: (49) 89 45 49 49 0 Fax: (49) 89 45 49 49 49 Zetex Inc. 47 Mall Drive, Unit 4 Commack NY 11725 USA Telephone: (631) 543-7100 Fax: (631) 864-7630 Zetex (Asia) Ltd. 3701-04 Metroplaza, Tower 1 Hing Fong Road, Kwai Fong, Hong Kong Telephone:(852) 26100 611 Fax: (852) 24250 494 These are supported by agents and distributors in major countries world-wide © Zetex plc 2001 www.zetex.com This publication is issued to provide outline information only which (unless agreed by the Company in writing) may not be used, applied or reproduced for any purpose or form part of any order or contract or be regarded as a representation relating to the products or services concerned. The Company reserves the right to alter without notice the specification, design, price or conditions of supply of any product or service. ISSUE 1 - JANUARY 2001 20