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器件描述：Understanding the Power Rating of Caddock MP9100 Resistors
器件厂商：ETC [ETC]
厂商主页：
文件大小：19.85KB
文件页数：2
PDF阅读：APPNOTESMP9100.pdf (点击阅读器件资料)
摘要：
T Heat Sink Temperature
R Thermal Resistance - Heat Sink to
Ambient Air or Reference Temperature
T Ambient or Reference Temperature
P
D
T Resistor Film Temperature (Max. 175°C)
R Thermal Resistance - Resistor Film
to Exposed Ceramic Case Interface
T Case Temperature (Exposed Ceramic Surface)
R Thermal Resistance - Case to Heat Sink
Surface (Pad or Thermal Grease)
Detail of
Cross Section
Center Line through Center
of Ceramic Element
Mounting Screw
Belleville Washer
Thermal Grease
or Pad
J
?JC
C
?CS
S
?SA
A
Heat Sink
(mounting surface)
CAD KDOC Applications Engineering Note: AEN-0102
Understanding the Power Rating
of Caddock MP9100 Resistors
Understanding the Power Rating
The maximum power rating of the Caddock MP9100
(TO-247 type) resistor is specified with the ceramic
surface maintained at 25°C using the same method
established and proven by power semiconductor
manufacturers over many years.
Caddock’s careful design practices and thorough re-
liability testing assure the user that the part will per-
form to all published specifications as long as its case
temperature (T
C
) does not exceed that specified in
Figure 1. Surge ratings must be observed.
In high power applications, the actual power dissipa-
tion capability of the resistor will be greatly depen-
dent on the heat sink, mounting method, interface ma-
terial characteristics and ambient temperature, (T
A
). The
maximum continuous power rating (100 Watts) for the
Caddock MP9100 resistor is based on a case tem-
perature (T
C
) of 25°C measured at the center of the
exposed ceramic surface. The Caddock MP9100 re-
sistor has a thermal resistance of 1.5°C/watt (R
?JC
),
from the junction (resistor film) to the case (exposed
ceramic case interface). For a case temperature (T
C
)
above 25°C, derating is necessary.
Allowable power dissipation (P
D
, watts) may be deter-
mined by the following equation.
Equation 1 P
D
=
Using the information provided in Fig 2, allowable
power dissipation and temperature gradients can be
estimated. Typical thermal resistance of various ma-
terials can be found in Table 1 on the next page. It
should be noted that material characteristics are those
provided by the manufacturers and these can vary
greatly if careful manufacturing processes are not ob-
served. Caddock suggests that actual temperature
measurements should be made under worst case con-
ditions to assure maximum reliability of a design.
CAD KDOC
? Caddock Electronics, 2002
Figure 2 MP9100 with Mounting Screw
and Belleville Washer
Figure 1
A copy of this Application Note can be obtained at www.caddock.com
(R
?JC
+ R
?CS
+ R
?SA
)
T
J
- T
A
100 %
80 %
60 %
40 %
20 %
0
25 100 175
% Rated Power
Case Temperature (T , °C)
g
C
MP9100 Derating Curve
Release Date: 9/20/02, Rev. A, Rev. Date: 9/20/02
Page 1 of 2
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