AN1941 Freescale Semiconductor / Motorola, AN1941 Datasheet - Page 4

• Manufacturer Part Number: AN1941
• Description: Modeling Thermal Effects in RF LDMOS Transistors
• Manufacturer: Freescale Semiconductor / Motorola

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RESULTS
careful selection of a fixture’s operating temperature and V
At lower quiescent currents (200 mA to 1000 mA), the
drain–source current has little dependence on temperature.
However, at higher levels of current (1000 mA to 3000 mA),
the greater slope of the curves indicates the increased
dependence on temperature. Figure 4 does not directly show
the effects of die temperature because T
temperature taken at the flange, not on the die. To plot I
T
directly at each V
• T
• T
AN1941
4
(die)
The results shown in Figure 4 illustrate the importance of
part must be labeled using the WIRE/PIN LABEL
function with the identical variable as in the equation.
The WIRE/PIN LABEL function allows wires or pins to
be defined with labels that can be used during
simulation or in post–simulation calculations.
(heat sink)
(flange)
, the following equation is needed to solve for T
: Calculated by ADS. The thermal port on the
Figure 4. MET Model T
: User–defined as a constant.
T
GS
(die)
:
= T
(heat sink)
Freescale Semiconductor, Inc.
+ T
(heat sink)
For More Information On This Product,
(flange)
(heat sink)
Sweep Simulation at Constant V
Go to: www.freescale.com
is the
DS
(die)
GS
vs.
MOTOROLA SEMICONDUCTOR APPLICATION INFORMATION
.
1. From the design file, click on Insert | Wire/Pin Label:
DS
and Parametric Values of V
GS