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TPS9103
POWER SUPPLY FOR GaAs POWER AMPLIFIERS
SLVS131A – OCTOBER 1995 – REVISED JULY 1996
14
POST OFFICE BOX 655303
DALLAS, TEXAS 75265
THERMAL INFORMATION
Implementation of integrated circuits in low-profile and fine-pitch packages requires special attention to power
dissipation. Many system-dependent issues such as thermal coupling, airflow, added heat sinks and convection
surfaces, and the presence of other heat-generating components affect the power-dissipation limits of a given
component.
Three basic approaches for enhancing thermal performance are listed below:
Improving the power-dissipation capability of the PWB design
Improving the thermal coupling of the component to the PWB
Introducing airflow in to the system
Using the given R
θ
JA
for this IC, the maximum power dissipation can be calculated with the equation:
TJmax
RJA
PDmax
TA
For the TPS9103, the power dissipation is in the PMOSFET. To calculate the power, use: I2
current through the device and R is the internal resistance as shown in the electrical characteristics table.
R where I is the
For a V
I
of 6 V, the resistance at 85
°
C is 0.210
. At a current of 2 A, the peak power dissipation is:
22
0.210
0.84 W
PD
Assuming a duty cycle of 1/8 or 0.125, the average power is:
0.84 W
0.125
0.105 W
The change in temperature is:
T = 0.105 W
×
154
°
C/W = 16.2
°
C
and the junction temperature is:
T
J
= 85
°
C + 16.2
°
C =101.2
°
C