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TCs are electrolytic capacitors that use tantalum as the anode material and passivated tantalum pentoxide as the dielectric. The advantages include greater capacitance per unit area and stabler voltage and temperature characteristics than large capacitance ceramic capacitors.
·Capacitor Comparison
Type
Aluminum Electrolytic Capacitor
Multilayer Ceramic Capacitor
Tantalum Capacitor
Film Capacitor
Dielectric
aluminum oxide
several ceramics
tantalum pentoxide
plastic film
Working Voltage
4 to 400V
6.3 to 250V
2.5 to 50V
50 to 1600V
Capacitance
47 to 10000µF
0.001 to 100µF
0.47 to 1000µF
0.001 to 10µF
Advantage
Wide array of breakdown voltages and capacitances
Good high frequency characteristics No polarity
Small package, Large, stable capacitance
High breakdown level No polarity
Disadvantage
Electrolyte leakage limits life Large package size There is polarity
Capacitance varies depending on voltage and temperature Cracking/chipping possible
The cathode terminal material differs between the two. Standard TCs use manganese dioxide (MnO2) while conductive polymer types (i.e. ROHM's TCO/TCTO series) feature an organic substance, which is less combustible and provides much lower ESR (Equivalent Series Resistance) characteristics (typically 1/10th). This makes them ideal for high frequency and large current applications.
The allowable ripple voltage must take a sine wave shape (see below). For other waveform types, please contact a ROHM representative. The permissible temperature increase due to ripple voltage/current is 5ºC max. At temperatures above this level the dielectric will begin to deteriorate, resulting in possible short-circuits. In order to determine the limits for the allowable ripple voltage at high temperatures, please refer to the following formulas: E=allowable ripple voltage E Max.(at50ºC)=0.7×E Max.(at 25ºC) E Max.(at85ºC)=0.5×E Max.(at 25ºC) E Max.(at125ºC)=0.3×E Max.(at 25ºC)
The allowable ripple current is calculated from the following formulas, which take into account ESR and power dissipation, which differ depending on the package type. P=I2R I = √(P/R) Please contact us for the ESR and power dissipation values.
Yes, ROHM's TCs must be derated at temperatures exceeding 85ºC (see graph below). Since the voltage supplied to the TC can take many forms and include transients (and possible overshooting), enough margin must be designed in. Many TC manufacturers are recommending using the TCs at 50% of the rated voltage.
The specifications and conditions for each characteristic are based on JIS standards (the particular JIS No. is listed on the datasheet of each product). Please refer to the JIS standard for relevant measurement methods.
Multilayer capacitors tend to decrease in capacitance as the temperature changes. TCs, on the other hand, are extremely stable under temperature fluctuations (see graph below), simplifying designs.
The lifetime of TCs is not clearly defined, since the normal factors that contribute to aging – drying up or leaking of the electrolyte in aluminum electrolytic capacitors.
