topic Re: About PMIC feedback line artwork in Power Management

About PMIC feedback line artwork

111kmw — Tue, 26 Jul 2022 23:48:25 GMT

Hi,

I have question about PMIC feedback line. (Specially NXP PMIC, FS84 and PF7100)

When we design the PCB, feedback signal is routed using line generally .

How about plane?

For example, there is power plane inner layer, and we connect power plane and feedback pin using via.

Is it ok? or Is it not good? (Because of high current...?)

Please give a answer.

Thanks,

guoweisun — Wed, 27 Jul 2022 03:53:06 GMT

Run feedback traces of the regulators in the inner layers to keep them shielded from
the power and noise nodes.

111kmw — Wed, 27 Jul 2022 04:19:50 GMT

hi, guoweisun

Thanks for your reply.

Your answer means "Don't connect diretly power plane and feedback pin using via."

Is it right?

Thanks,

guoweisun — Wed, 27 Jul 2022 06:10:15 GMT

Correct!

111kmw — Wed, 27 Jul 2022 06:39:02 GMT

Thanks, guoweisun!

Could you explain why feedback line should be shielded from the power? (not Switching node)

Because power plane's current can be changed?

Please give me answer!

Thanks,

guoweisun — Thu, 28 Jul 2022 02:38:01 GMT

The power path combine with more noise including high frequency/low frequency which will affect with FB signal.