I'm trying to choose a voltage regulator, and considering I will have a relay on my PCB it seems a switching regulator is the better choice for the coil noise. Example Reference

I found a lot of schematic examples over the internet, and a lots use a switching regulator when have relays. I don't know if it is coincidence, or it is really better for the coil noises.

  1. Is it really true?
  2. How can I choose a good switching regulator to help with the noises? A higher switching frequency will be better?
  3. My PCB operates in 3.3V, and I'm considering use this regulator MCP16311. If I use a Vin 12V or 5V it will make any diference with the noises handle?

Edited: By noise, I'm referring electrical noise caused by the relay coil operation, which can makes the microcontroller reset

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    \$\begingroup\$ Noise can mean a lot of things in electronics design. I'm not clear what you're asking; I suggest you clarify exactly what you mean by "noise", each time you reference it. For instance, coils can make "noise" meaning audible sound but you might also be referring to electronic noise meaning small unwanted currents/voltages. \$\endgroup\$
    – uint128_t
    Commented Sep 24, 2017 at 15:29
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    \$\begingroup\$ @uint128_t sorry about that. I edited the post... my point is about electrical noise. I included some capacitors, but when my relay operates the MCU is still resetting. I'm trying to avoid the resets by changing the linear regulator for a switching regulator \$\endgroup\$ Commented Sep 24, 2017 at 15:41
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    \$\begingroup\$ I'm trying to avoid the resets by changing the linear regulator for a switching regulator I give you 0% chance of success with that. Follow the suggestions in my answers to solve this. \$\endgroup\$ Commented Sep 24, 2017 at 15:44
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    \$\begingroup\$ It sounds like the type of regulator is not your issue. Rather, you need to better supply isolation and supply decoupling if your MCU is resetting when the relay fires. You haven't posted your circuit (schematic and PCB) so it's tough to tell what could be causing the reset. \$\endgroup\$
    – uint128_t
    Commented Sep 24, 2017 at 15:44
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    \$\begingroup\$ @BrunoAraujo - FYI, this has been an example of "the XY problem". Your real problem (disclosed later :-) ) is "when my relay operates the MCU is still resetting" (X). You thought that this problem was related to differences between linear & switching power supplies (it isn't), and so asked about those differences (Y). In some XY-problems, focussing on question (Y) can completely derail any chance of finding and fixing the real, original problem (X). I recommend reading the link I gave, to help with future troubleshooting. \$\endgroup\$
    – SamGibson
    Commented Sep 24, 2017 at 16:21

1 Answer 1


There is no general truth, switched regulators aren't always the best choice.

Using a relay by itself has nothing to do with the need for a switched regulator. What is the case is that a relay uses some current when activated. Depending on the relay this increased supply current can be a good reason to use a switched regulator.

For circuits with a low supply current, for example less than 10 mA, using a switched regulator makes little sense. The power loss due to a linear regulator will be small at 10 mA or less.

For large currents, for example 100 mA and higher, it starts to make sense to use a switched regulator as the power dissipation of a linear regulator is becoming significant and you might need a heatsink. This might add more cost than using a switched regulator.

Of course it also depends on the difference between regulator input and output voltage difference. When the difference is small, a linear regulator might be a better choice.

Switched regulators produce ripple at the output voltage this is due to their switching nature. I would not call this "noise", a better word is "switching noise". Noise is inherently random and this ripple is not.

Most circuits especially digital/logic/micro controllers are quite immune to this ripple so there is little need to worry about it. Usually only analog circuits like RF circuits, filters, ADCs are sensitive to this ripple so then a linear regulator or additional supply filtering might be needed. It is also possible to us a switched regulator to for example, drop from 12 V to 5 V and then use an LDO (linear regulator) to drop 5 V to 3.3 V for a sensitive circuit.

If the a signal (not noise!) from the relay resets the micro you have a design issue! You should use a flyback diode across the relay's coil and add a decoupling capacitor near the relay and near the micro. This has nothing to do with linear vs switched regulators but everything to do with proper design.


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