1SMC5379 View Datasheet(PDF) - PANJIT INTERNATIONAL
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1SMC5379 Datasheet PDF : 5 Pages
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3. SURGE CURRENT (Ir) - Surge current is specified as the maximum allowable peak, non-recurrent square-wave
current with a pulse width, PW, of 8.3 ms. The data given in Figure 5 may be used to find the maximum surge
current for a quare wave of any pulse width between 1 ms and 1000ms by plotting the applicable points on
logarithmic paper. Examples of this, using the 6.8v and 200V zeners, are shown in Figure 6. Mounting
contact
located
as
specified
in
Note
3.
(TA=25
¢J
¡Ï¢·¢J
¡Ð¢±
).
4. VOLTAGE REGULATION (£GVz) - Test conditions for voltage regulation are as follows: Vz measurements are made
at 10% and then at 50% of the Iz max value listed in the electrical characteristics table. The test currents are the
same for the 5% and 10% tolerance devices. The test current time druation for each Vz measurement is 40 ¡Ó 10 ms.
(TA=25
¢J
¡Ï¢·¢J
¡Ð¢±
).
Mounting
contact
located
as
specified
in
Note2.
5. MAXIMUM REGULATOR CURRENT (IZM) - The maximum current shown is based on the maximum voltage of a
5% type unit. Therefore, it applies only to the B-suffix device. The actual IZM for any device may not exceed the
value of 5 watts divided by the actual Vz of the device. TL=75 ¢J at maximum from the device body.
APPLICATION NOTE:
Since the actual voltage available from a given zener
diode is temperature dependent, it is necessary to
determine junction temperature under any set of
operating conditions in order to calculate its value. The
following procedure is recommended:
Lead Temperature, TL, should be determined from:
TL = £c LAPD + TA
£c LA is the lead-to-ambient thermal resistance (¢J /W)
and PD is the power dissipation.
Junction Temperature, TJ , may be found from:
TJ = TL + £GTJL
£GTJL is the increase in junction temperature above the
lead temperature and may be found from Figure 3 for
a train of power pulses or from Figure 4 for dc power.
£G TJL = £c JLPD
For worst-case design, using expected limits of Iz, limits
of PD and the extremes of TJ(£GTJ) may be estimated.
Changes in voltage, Vz, can then be found from:
£GV = £c VZ £G TJ
£c VZ, the zener voltage temperature coefficient, is fount
from Figures 2.
Under high power-pulse operation, the zener voltage will
vary with time and may also be affected significantly be
the zener resistance. For best regulation, keep current
excursions as low as possible.
Data of Figure 3 should not be used to compute surge
capability. Surge limitations are given in Figure 5. They
are lower than would be expected by considering only
junction temperature, as current crowding effects cause
temperatures to be extremely high in small spots resulting
in device degradation should the limits of Figure. 5 be
exceeded.
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