ALUMINUM ORGANIC CAPACITORS
Performance Characteristics
R
L
- Capacitor Leakage Resistance. Typically it can
be 35 K to 2.5 MOhms depending on voltage -
capacitance. It can exceed 10
12
ohms in monolithic
ceramics and in film capacitors.
R
d
- The dielectric loss contributed by dielectric
absorption and molecular polarization. It becomes
very significant in high frequency measurements and
applications. Its value varies with frequency.
C
d
- The inherent dielectric absorption of the solid
aluminum capacitor.
As frequency increases, X
c
continues to decrease
according to its equation. There is unavoidable
inductance as well as resistance in all capacitors,
and at some point in frequency, the reactance ceas-
es to be capacitive and becomes inductive. This fre-
quency is call the self-resonant point.
Figure 4 compares the frequency response of an
AO-CAP to a Tantalum chip. Maximum limits for 100
kHz ESR are listed in the part number tables for
each series.
10. Ripple Current/Voltage
Permissible AC ripple voltage and current are related
to equivalent series resistance (ESR) and power dis-
sipation capability.
Permissible ripple current which may be applied
is limited by two criteria:
a. The resulting voltage across the capacitor with the
summation of DC bias and peak voltage of the
AC portion must not exceed the rated voltage of
the capacitor.
b. The negative peak AC voltage, in combination
with bias voltage, if any, must not exceed the per-
missible reverse voltage ratings presented in
Section 5.
Actual power dissipated may be calculated from the
following:
P = I
2
R
Substituting I = E ; P = E
2
R
Z
Z
2
Using P max from Table 3, maximum allowable rms
ripple current or voltage may be determined as fol-
lows:
Figure 4.
9. AC Power Dissipation
Power dissipation is a function of capacitor size and
materials. Maximum power ratings have been estab-
lished for all case sizes to prevent overheating. In
actual use, the capacitor's ability to dissipate the
heat generated at any given power level may be
affected by a variety of circuit factors. These include
board density, pad size, heat sinks and air circulation.
Power capability is determined based on a 20°C tem-
perature rise. A higher temperature rise and therefore
higher power capability is allowable as long as the
ambient temperature plus temperature rise due to rip-
ple current does not exceed the rated temperature of
the part.
Case Code
KEMET
V
D
X
EIA
7343-20
7343-31
7343-43
Maximum Power Dissipation mWatts
@ +25°C with 20° Temperature Rise
270
250
225
I
max =
P
max
ESR
E
max =
Z
P
max
R
Where:
I
max
= Maximum rupple current (ARMS)
P
max
= Maximum Power @ allowable
∆T
normally
+20°C
E
max
= Maximum ripple voltage (VRMS)
Refer to part number listings for permittable Arms
limits.
Table 3 - AO Capacitor Power Dissipation Ratings
60
©KEMET Electronics Corporation, P.O. Box 5928, Greenville, S.C. 29606, (864) 963-6300
Aluminum Organic Capacitors
Where:
I = rms ripple current (Amperes)
E = rms ripple voltage (Volts)
P = power (Watts)
Z = impedance at specified frequency (ohms)
R = ESR(Ohms)
KEMET [ KEMET CORPORATION ]
