DPA switch Designs

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My design pi-expert DPA switch (DPA425PN) recommends capacitor output filter (EKZE ***ELL *** MJ25S)

(United Chemi-C).

These capacitors can operate at switching frequencies of 400kHz?

Epcos B41858 capacitors can also operate at frequencies 400kHz smoothly?


I would be grateful if someone answered.





DPA-Switch_PIDesign5.pdf2 MB



We sometimes do use electrolytic capacitors for that type of supply (http://www.powerint.com/sites/default/files/PDFFiles/der43.pdf) however pretty often you need to check on a prototype if the behavior is acceptable. ESL will have a bigger impact at these frequencies, and so ripple may not be filtered well enough for your application. You should also pay close attention to the temperature of the capacitor, just to be sure that you are evenly distributing the ripple current through multiple capacitors, and also to check that the capacitors are not getting too hot. Layout is very important to guarantee that currents are evenly distributed through the different caps. Also, if you are concerned about too much ripple, you can use a ceramic cap (or oscon, or tantalum) before the electrolytics.