MMBT5087L

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6

Figure 14. Thermal Response

t, TIME (ms)

1.0

0.01

0.01

0.02

0.03

0.05

0.07

0.1

0.2

0.3

0.5

0.7

0.02

0.05

0.1

0.2

0.5

1.0

2.0

5.0

10

20

50

100

200

500

1.0k 2.0k

5.0k 10k

20k 50k 100k

D = 0.5

0.2

0.1

0.05

0.02

0.01

SINGLE PULSE

D CURVES APPLY FOR POWER

PULSE TRAIN SHOWN

FIGURE 16

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0

Figure 15. Typical Collector Leakage Current

DESIGN NOTE: USE OF THERMAL RESPONSE DATA

A train of periodical power pulses can be represented by

the model as shown in Figure 16. Using the model and the

device thermal response the normalized effective transient

thermal resistance of Figure 14 was calculated for various

duty cycles.

Example:

Dissipating 2.0 watts peak under the following conditions:

Using Figure 14 at a pulse width of 1.0 ms and D = 0.2, the

reading of r(t) is 0.22.

The peak rise in junction temperature is therefore

For more information, see ON Semiconductor Application

Note AN569/D, available from the Literature Distribution

Center or on our website at www.onsemi.com.

-2

0

0

+ 20

+ 40

+ 60

+ 80 + 100 + 120 + 140 + 160

AND