®
Accu-P
Performance Characteristics RF Power Applications
ESR and therefore RF heating. Values of ESR for
RF POWER APPLICATIONS
In RF power applications capacitor losses generate heat. Two
factors of particular importance to designers are:
Accu-P® capacitors are significantly less than those of
ceramic MLC components currently available.
• Minimizing the generation of heat.
• Dissipating heat as efficiently as possible.
HEAT DISSIPATION
• Heat is dissipated from a capacitor through a variety of
paths, but the key factor in the removal of heat is the
thermal conductivity of the capacitor material.
• The higher the thermal conductivity of the capacitor, the
more rapidly heat will be dissipated.
• The table below illustrates the importance of thermal
conductivity to the performance of Accu-P® in power
applications.
CAPACITOR HEATING
• The major source of heat generation in a capacitor in RF
power applications is a function of RF current (I) and ESR,
from the relationship:
Power dissipation = I2RMS x ESR
• Accu-P® capacitors are specially designed to minimize
PRODUCT
MATERIAL
Alumina
Magnesium Titanate
THERMAL CONDUCTIVITY WꢀmK
Accu-P®
18.9
6.0
Microwave MLC
Power Handling
®
Accu-P 10pF
Data used in calculating the graph:
Thermal impedance of capacitors:
0402
0603
0805
1210
17ꢀC/W
12ꢀC/W
6.5ꢀC/W
5ꢀC/W
Thermal impedance measured using RF generator,
amplifier and strip-line transformer.
ESR of capacitors measured on Boonton 34A
The thermal impedance expresses the temperature difference
in ꢀC between chip center and termination caused by
a power dissipation of 1 watt in the chip. It is expressed in
ꢀC/W.
THERMAL IMPEDANCE
Thermal impedance of Accu-P® chips is shown below com-
pared with the thermal impedance of Microwave MLC’s.
CAPACITOR TYPE
Accu-P®
CHIP SIZE
0805
1210
THERMAL IMPEDANCE (°C/W)
6.5
5
Microwave MLC
0505
1210
12
7.5
ADVANTAGES OF ACCU-P®
IN RF POWER CIRCUITS
PRACTICAL APPLICATION
IN RF POWER CIRCUITS
• There is a wide variety of different experimental methods
for measuring the power handling performance of a
capacitor in RF power circuits. Each method has its
own problems and few of them exactly reproduce the
conditions present in “real” circuit applications.
• Similarly, there is a very wide range of different circuit appli-
cations, all with their unique characteristics and operating
conditions which cannot possibly be covered by such
“theoretical” testing.
The optimized design of Accu-P® offers the designer of RF
power circuits the following advantages:
• Reduced power losses due to the inherently low ESR of
Accu-P®.
• Increased power dissipation due to the high thermal
conductivity of Accu-P®.
• THE ONLY TRUE TEST OF A CAPACITOR IN ANY PARTICULAR
APPLICATION IS ITS PERFORMANCE UNDER OPERATING
CONDITIONS IN THE ACTUAL CIRCUIT.
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