MZ4625 Datasheet, PDF (41/42 Pages) Motorola, Inc – 500 mW DO-35 Glass Zener Voltage Regulator Diodes

1N5333B through 1N5388B
1000
T = 25°C
100
100
10
10
1
0.1
10
20
30
40
50
60
70
80
VZ, ZENER VOLTAGE (VOLTS)
Figure 9. Zener Voltage versus Zener Current
VZ = 11 thru 75 Volts
1
0.1
80
100
120
140 160
180
200 220
VZ, ZENER VOLTAGE (VOLTS)
Figure 10. Zener Voltage versus Zener Current
VZ = 82 thru 200 Volts
APPLICATION NOTE
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 = θ_LA PD + TA
θ_LA is the lead-to-ambient thermal resistance and PD is the
power dissipation.
Junction Temperature, TJ, may be found from:
TJ = TL + ∆TJL
∆TJL is the increase in junction temperature above the lead
temperature and may be found from Figure 4 for a train of
power pulses or from Figure 5 for dc power.
∆TJL = θ_JL PD
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 = θ_VZ ∆TJ
θ_VZ, the zener voltage temperature coefficient, is found from
Figures 2 and 3.
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.
Data of Figure 4 should not be used to compute surge capa-
bility. Surge limitations are given in Figure 6. They are lower
than would be expected by considering only junction tempera-
ture, as current crowding effects cause temperatures to be ex-
tremely high in small spots resulting in device degradation
should the limits of Figure 6 be exceeded.
Devices listed in bold, italic are Motorola preferred devices.
Motorola TVS/Zener Device Data
5 Watt Surmetic 40 Data Sheet
6-137