January 1999 TOKO, Inc.

Page 11

TK116xxU

PD

Dpd

25

50

75

150

(mW)

TA (°C)

3

6

5

4

0

50

100

150

TA (°C)

0

600

1000

200

400

800

MOUNTED AS

SHOWN

FREE AIR

DEFINITION AND EXPLANATION OF TECHNICAL TERMS (CONT.)

SOT-89 POWER DISSIPATION CURVE

thermal equilibrium is reached. The range of usable currents

can also be found from the graph below:

Procedure:

1) Find P

D

2) P

3) Plot P

4) Connect P

with a straight line.

5) In design, take a vertical line from the maximum operating

temperature (e.g., 75

°C.) to the derating curve.

6) Read off the value of P

The maximum operating current is:

I