EXV226M6R3A9BAA Datasheet, PDF (11/18 Pages) Kemet Corporation – Surface Mount Aluminum Electrolytic Capacitors

Surface Mount Aluminum Electrolytic Capacitors – EXV Series, +105°C
Impedance (Z) cont’d
Impedance as a function of frequency (sinusoidal waveform) for different temperature values can be represented as follows
(typical values):
Z (ohm)
1,000
10 µF
100
-40°C
10
20°C
1
85°C
0.1
0.1
1
10
100
1,000
10,000
F (K Hz)
R_e is the most temperature-dependent component of an electrolytic capacitor equivalent circuit. Electrolyte resistivity will
decrease if temperature rises.
In order to obtain a low impedance value throughout the temperature range, R_e must be as little as possible. However, R_e
values that are too low indicate a very aggressive electrolyte, resulting in a shorter life of the electrolytic capacitor at high
temperatures. A compromise must be reached.
Leakage Current (LC)
Due to the aluminum oxide layer that serves as a dielectric, a small current will continue to flow even after a DC voltage has
been applied for long periods. This current is called leakage current.
A high leakage current flows after applying voltage to the capacitor then decreases in a few minutes, e.g., after prolonged
storage without any applied voltage. In the course of continuous operation, the leakage current will decrease and reach an
almost constant value.
After a voltage-free storage the oxide layer may deteriorate, especially at high temperature. Since there are no leakage
currents to transport oxygen ions to the anode, the oxide layer is not regenerated. The result is that a higher than normal
leakage current will flow when voltage is applied after prolonged storage.
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