Datasheet > 1N749ADTA

1N749ADTA

更新时间： 2023-01-02 17:57:39

品牌	Logo	应用领域
摩托罗拉 - MOTOROLA		/
页数	文件大小	规格书
8页	69K
描述
Zener Diode, 4.3V V(Z), 1%, 0.5W, Silicon, Unidirectional, DO-204AH, HERMETIC SEALED, GLASS, DO-35, 2 PIN

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1N749ADTA 数据手册

GENERAL DATA — 500 mW DO-35 GLASS

APPLICATION NOTE — ZENER VOLTAGE

500

400

300

200

100

Since the actual voltage available from a given zener diode

is temperature dependent, it is necessary to determine junc-

tiontemperatureunderanysetofoperatingconditionsinorder

to calculate its value. The following procedure is recom-

mended:

Lead Temperature, T , should be determined from:

T = θ

LA D

+ T .

2.4–60 V

isthelead-to-ambientthermalresistance(°C/W)andP is

the power dissipation. The value forθ willvaryanddepends

onthedevicemountingmethod.θ isgenerally30to40°C/W

for the various clips and tie points in common use and for

printed circuit board wiring.

62–200 V

0.6

0.2

0.4

0.8

The temperature of the lead can also be measured using a

thermocoupleplacedontheleadascloseaspossibletothetie

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-

L, LEAD LENGTH TO HEAT SINK (INCH)

Figure 2. Typical Thermal Resistance

1000

7000

5000

sured value of T , the junction temperature may be deter-

TYPICAL LEAKAGE CURRENT

AT 80% OF NOMINAL

BREAKDOWN VOLTAGE

mined by:

T = T + ∆T .

2000

1000

∆T is the increase in junction temperature above the lead

700

temperature and may be found from Figure 2 for dc power:

500

∆T = θ P .

JL JL D

200

For worst-case design, using expected limits of I , limits of

100

P andtheextremesofT (∆T )maybeestimated.Changesin

voltage, V , can then be found from:

∆V = θ T .

VZ J

, 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

zenerresistance. Forbestregulation, keepcurrentexcursions

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.

0.7

0.5

+125°C

0.2

0.1

0.07

0.05

0.02

0.01

0.007

0.005

+25°C

0.002

0.001

12 13 14 15

V , NOMINAL ZENER VOLTAGE (VOLTS)

Figure 3. Typical Leakage Current

Motorola TVS/Zener Device Data

500 mW DO-35 Glass Data Sheet

6-3

1 234 5 6 7 8

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