LMR33620: Webench Asks for 5 Output Caps - Does this make sense?

Max Henzi

Part Number: LMR33620

Hello,
I am using the LMR33620ADDA to provide 9.5V at 1.5A from an input supply of 10.5V to 18V. I've used Webench to create the design. Webench is asking for 5 15UF output capacitors with an "effective" capacitance of 16UF. Won't 5 15 UF capacitors give a much higher effective capacitance than 16UF? I can see using perhaps 2 capacitors . . . but, why 5? Just want to double check before committing the design to a prototype.

Thanks for your help,

Max

over 2 years ago

+1 Samuel Jaffe over 2 years ago

TI__Mastermind 25590 points

Max,

A capacitor's capacitance will derate depending on the voltage applied (see the capacitor datasheet, example). Selecting a 10V rated capacitor for a 9.5V application, for example, may derate 15uF down to 3uF. This is why we recommend using a capacitor with at least 2x the rated voltage for the application. So to answer your question, yes you can instead use 2x15uF capacitors which derate to 8uF which would give you 16uF total.

-Sam

0 Max Henzi over 2 years ago in reply to Samuel Jaffe

Prodigy 250 points

Thank you very much!
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LMR33620: Webench Asks for 5 Output Caps - Does this make sense?