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  • What are the features of tantalum capacitors (TCs)?
    • 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
      TypeAluminum Electrolytic CapacitorMultilayer Ceramic CapacitorTantalum CapacitorFilm Capacitor
      Dielectricaluminum oxideseveral ceramicstantalum pentoxideplastic film
      4 to 400V6.3 to 250V2.5 to 50V50 to 1600V
      Capacitance47 to 10000µF0.001 to 100µF0.47 to 1000µF0.001 to 10µF
      AdvantageWide array of
      breakdown voltages
      and capacitances
      Good high frequency
      No polarity
      Small package,
      stable capacitance
      High breakdown level
      No polarity
      DisadvantageElectrolyte leakage limits life
      Large package size
      There is polarity
      Capacitance varies
      depending on voltage
      and temperature
      Cracking/chipping possible
      Short-circuit possible
      There is polarity
      Small capacitance
      Less package variety
  • What is the difference between standard and conductive polymer TCs?
    • 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.

      Conductive Polymer TC

      Standard TC
  • What are the allowable levels for ripple voltage and current?
    • 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)
  • What is the current limit?
    • 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.
      I = √(P/R)
      Please contact us for the ESR and power dissipation values.
  • Do TCs require derating?
    • 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.
  • Do TCs have a lifetime?
    • 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.
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