TK712xx
DEFINITION AND EXPLANATION OF TECHNICAL TERMS (CONT.)
The range of usable currents can also be found from the
graph below.
(mW)
3
P
D
6
D
PD
4
5
25
50
75
(°C)
150
T
A
Procedure:
1) Find PD
2) PD1 is taken to be PD x (~ 0.8 - 0.9)
3) Plot PD1 against 25 °C
4) Connect PD1 to the point corresponding to the 150 °C
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 PD against the point at which the
verticallineintersectsthederatingcurve. Thisistaken
as the maximum power dissipation, DPD
.
The maximum operating current is:
IOUT = (DPD / (VIN(MAX) - VOUT
)
1000
800
600
400
MOUNTED
FREE AIR
200
0
0
50
100
150
T
(°C)
A
SOT-25 POWER DISSIPATION CURVE
Page 16
January 1999 TOKO, Inc.
TOKO [ TOKO, INC ]
