1
\$\begingroup\$

I was recently told that it could be a good approach to use different voltage regulators to different IC's on the board. So if I have the MCU and then a different IC somewhere, even though they require same voltage I should use 2 different voltage regulators so one wouldn't send back some noise to the other through the same line.

Is that really considerable or I could just eliminate that with some decoupling capacitors next to each IC (as usually datasheets suggest)?

\$\endgroup\$
4
\$\begingroup\$
  • Generally, use a common supply for all devices on the same voltage.
  • Use a separate regulator if switching noisy devices.
  • Separate regulators should be considered for audio and digital circuits in the same device as digital switching noise may show up on the audio line.
  • Always decouple every IC. This site has many questions regarding non-working circuits because the OP assumed they were optional components added at the whim of the datasheet authors.

Is a MCU considered to be a noise generator?

Any time anything switches there is a change in current. There will be a short delay while the power-supply voltage regulator reacts and the inductance of the wiring or PCB traces will make the situation worse. The local capacitor provides a tiny but fast acting charge reservoir to hold the voltage steady.


Responses to OP's comments.

If most MCU's have internal voltage regulator to work in a lower voltage than its input, why the decoupling capacitor is always required on the datasheets?

Most don't. The only ones that come to mind would be an ADC or DAC voltage reference. The de-coupling is still required for reasons stated above.

Search this site for "decoupling" and you will find plenty of info on the subject.

|improve this answer|||||
\$\endgroup\$
  • \$\begingroup\$ Thanks. But now 2 questions came into my mind: Is a MCU considered to be a noise generator? If most MCU's have internal voltage regulator to work in a lower voltage than its input, why the decoupling capacitor is always required on the datasheets? \$\endgroup\$ – Felipe_Ribas Aug 27 '16 at 9:57
  • \$\begingroup\$ See the update. \$\endgroup\$ – Transistor Aug 27 '16 at 10:18

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

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