2
\$\begingroup\$

I have a kind of an open-ended question.

If I'm designing a board with a buck converter and have picked out my peripherals, and say for example I want to run my CAN FD interface at 1MHz baud and maybe a SPI signal at 1MHz, and I am now looking at power supply design.

I am looking at a buck switching regulator which has a switching frequency at 1.4MHz. Is there any big EMI issues with having the switching frequency so close to the frequency of my other signals running through the board? Should I aim at either a higher or lower frequency?

Pretty open-ended question, but I never really thought of it until I ran into it.

\$\endgroup\$
3
  • \$\begingroup\$ This question is too open. If you have no coupling between the switching freq. and SPI, then it does not matter. But if you have a coupling, it might be best to keep the frequencies apart as far as possible. So what could be a good advice here? \$\endgroup\$
    – Stefan Wyss
    Commented Jun 23, 2020 at 17:46
  • \$\begingroup\$ @StefanWyss Hmm, maybe I can expand. The power from the buck converter would be used on the power plane to power both a microcontroller and peripheral devices. Expected stackup is sig - gnd - power - sig. \$\endgroup\$
    – Punchki
    Commented Jun 23, 2020 at 17:52
  • \$\begingroup\$ How much filter attenuation do you have inside that power distribution? \$\endgroup\$
    – Stefan Wyss
    Commented Jun 23, 2020 at 17:56

1 Answer 1

Reset to default
2
\$\begingroup\$

If the regulator were that bad it'd screw up the board operation no matter what.

If you had a radio in there, then having a regulator switching at the RF frequency or a sub-multiple of it could be an issue (as could having a microprocessor clock close to a frequency you care about). But CAN and SPI aren't going to notice anything that won't generally make the whole board unable to function.

\$\endgroup\$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.