MMBT3416LT3G

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6

Figure 19. 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 100

D = 0.5

0.2

0.1

0.05

0.02

0.01

SINGLE PULSE

D CURVES APPLY FOR POWER

PULSE TRAIN SHOWN

FIGURE 19A

Figure 19A.

-4

0

Figure 20.

400

2.0

DESIGN NOTE: USE OF THERMAL RESPONSE DATA

A train of periodical power pulses can be represented by the

model as shown in Figure 19A. Using the model and the device

thermal response the normalized effective transient thermal

resistance of Figure 19 was calculated for various duty cycles.

Example:

The MPS3904 is dissipating 2.0 W peak under the following

conditions:

Using Figure 19 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 AN−569.

transistor that must be observed for reliable operation. Collector

load lines for specific circuits must fall below the limits indicated

by the applicable curve.

is variable depending upon conditions. Pulse curves are valid for

calculated from the data in Figure 19. At high case or ambient

temperatures, thermal limitations will reduce the power that can

be handled to values less than the limitations imposed by second

breakdown.

-2

0

0

+ 20

+ 40

+ 60

+ 80 + 100 + 120 + 140 + 160

AND

CURRENT LIMIT

THERMAL LIMIT

SECOND BREAKDOWN LIMIT

1.0 ms

10

ms

1.0 s

dc

dc

4.0

6.0

10

20

40

60

100

200

4.0

6.0

8.0

10

20

40

100

ms