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Q:

How much do I need to derate polymer capacitors?

A:

Surface mount tantalum capacitors typically have derating guidelines associated with them, regardless of capacitor manufacturer. The derating guideline is different based on the cathode material used in the construction.

Guidelines to Derate Polymer Capacitors

This information applies to Polymer Electrolytic capacitors with a Ta2O5 dielectric and PEDOT cathode system. These capacitors are also known as KO-CAP. For Tantalum-MnO2 type capacitors, see this question.

For polymer electrolytic capacitors, the typical voltage derating for the capacitor depends on its rated voltage. If the rated voltage is ≤10V, the recommended derating is 10%. However, if the rated voltage of the capacitor is >10V, then the recommended derating is 20%. These derating guidelines are typically specified to 105°C. Additional derating may be necessary up to 125°C.

T525 derate polymer capacitors chart

Figure 1 – T525 Derate Polymer Capacitors Chart Example

Look for a derating or “recommended application voltage” section of a data sheet for more information. As an example, Figure 1 is the derating curve for a KEMET T525 KO-CAP Polymer Electrolytic capacitor.

 

Added on:

Tuesday, August 18th, 2015