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UCC27282-Q1: Selecting bootstrap capacitor

Part Number: UCC27282-Q1

Hi all,

Following the indications in UCC27282-Q1 datasheet (section 8.2.2.1), I'm calculating the value of bootstrap capacitor.

My input data are:

- VDD = 10V

- Qg (MOSFET gate charge) = 178nC

- Switching frequency = 20KHz

So I selected the 470nF 25V X8R SMD Chip Multilayer Ceramic Capacitor  ( Murata GCJ188R91E474KA01 ).

In the previous section 7.3.6 ( Negative voltage transients ), I read that the capacitor from HB to HS has to be with Low ESR, therefore:

- Is my selected capacitor not good for the application?

- Does the bootstrap capacitor has to be electrolitic?

Regards,

Lorenzo

  • Hello Lorenzo,

    Thank you for the interest in the UCC27282-Q1. I think most datasheets we recommend for the VDD and HB-HS capacitors to use a high grade dielectric ceramic capacitor such as X7R or COG. I see that the X8R is similar to X7R but with higher temperature rating, so this is a good choice for the bootstrap capacitor.

    Ceramic capacitors are very low ESR so the capacitor you chose is preferred. The electrolytic capacitors are usually higher ESR than ceramic.

    Confirm if this addresses your questions, or you can post additional questions on this thread.

    Regards,