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MZ4625 Folha de dados(PDF) 2 Page - Motorola, Inc |
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MZ4625 Folha de dados(HTML) 2 Page - Motorola, Inc |
2 / 42 page GENERAL DATA — 500 mW DO-35 GLASS Motorola TVS/Zener Device Data 6-98 500 mW DO-35 Glass Data Sheet APPLICATION NOTE — ZENER VOLTAGE Since the actual voltage available from a given zener diode is temperature dependent, it is necessary to determine junc- tion temperature under any set of operating conditions in order to calculate its value. The following procedure is recom- mended: Lead Temperature, TL, should be determined from: TL = θLAPD + TA. θLAisthelead-to-ambientthermalresistance(°C/W)andPDis the power dissipation. The value for θLA will vary and depends on the device mounting method. θLA is generally 30 to 40°C/W for the various clips and tie points in common use and for printed circuit board wiring. The temperature of the lead can also be measured using a thermocouple placed on the lead as close as possible to the tie point. The thermal mass connected to the tie point is normally large enough so that it will not significantly respond to heat surges generated in the diode as a result of pulsed operation once steady-state conditions are achieved. Using the mea- sured value of TL, the junction temperature may be deter- mined by: TJ = TL + ∆TJL. ∆TJL is the increase in junction temperature above the lead temperature and may be found from Figure 2 for dc power: ∆TJL = θJLPD. For worst-case design, using expected limits of IZ, limits of PD and the extremes of TJ(∆TJ) may be estimated. Changes in voltage, VZ, can then be found from: ∆V = θVZTJ. θVZ, the zener voltage temperature coefficient, is found from Figures 4 and 5. Under high power-pulse operation, the zener voltage will vary with time and may also be affected significantly by the zener resistance. For best regulation, keep current excursions as low as possible. Surge limitations are given in Figure 7. They are lower than would be expected by considering only junction temperature, as current crowding effects cause temperatures to be ex- tremely high in small spots, resulting in device degradation should the limits of Figure 7 be exceeded. LL 500 400 300 200 100 0 0 0.2 0.4 0.6 0.8 1 2.4–60 V 62–200 V L, LEAD LENGTH TO HEAT SINK (INCH) Figure 2. Typical Thermal Resistance TYPICAL LEAKAGE CURRENT AT 80% OF NOMINAL BREAKDOWN VOLTAGE +25 °C +125 °C 1000 7000 5000 2000 1000 700 500 200 100 70 50 20 10 7 5 2 1 0.7 0.5 0.2 0.1 0.07 0.05 0.02 0.01 0.007 0.005 0.002 0.001 34 5 6 7 8 9 10 11 12 13 14 15 VZ, NOMINAL ZENER VOLTAGE (VOLTS) Figure 3. Typical Leakage Current |
Nº de peça semelhante - MZ4625 |
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Descrição semelhante - MZ4625 |
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