When selecting a suitable Tantalum Capacitor for your application, its rated voltage and temperature are one of important factors to consider. For optimal performance and long term reliability, derating is often considered.
Kemet’s T491 series of tantalum surface mount capacitors is an example to show the derating guideline table.
The above table shows the relationship between the percentage of applied rated voltage of the capacitor and the temperature. An area about Recommended Maximum Application Voltage shows the recommended steady state operating voltage for continuous operation and optimal reliability at the given temperature. If the actual application temperature is lower than 85°C, the tantalum capacitor is suggested to be run at just 50% of its rated maximum working voltage. Therefore, if a 50V rated capacitor would now be considered a 25V at 85°C (50V x 50% = 25V).
Due to different in the material structure of tantalum capacitors, their derating guideline tables are quite different.