Electrolytic Cap in PCB

[NMP]

Hi all,

I just made a project with a uP, check all the datashets, folow the decoupling rules and some evm of the components, made the firmware and It all was working well.

with 3 or more boards connected to the same power supply, if i insert a new one, or disconnect and connect one of them, all the boards make a reset.

If i put a Electrolytic cap on each one  all works well.

Does anyone know how can i prevent/read this?

[tszaboo]

Without knowing more about the setup, I would say, as a general rule:
Include a "bulk" electrolytic capacitor on your PCB, if possible, one per rail. They have ESR, which helps dissipating transients, they provide current when it is needed, they reduce the current spikes, and intermittent voltage drops on cables.

[danadak]

Post schematic and identify the electrolytic you are adding.


Regards, Dana.

[NMP]

Thank's!!
One per Rail makes sense..
I have it all in SMD, I see some tantalum, big yellow ones in a lot of projects, but there are some 0805 for instance 47uF, do you think it whould do the job?

[Jeroen3]

0805 for instance 47uF

Beware, those are expensive and low voltage.

[tszaboo]

Thank's!!
One per Rail makes sense..
I have it all in SMD, I see some tantalum, big yellow ones in a lot of projects, but there are some 0805 for instance 47uF, do you think it whould do the job?

Well, the 0805 47uF will have 0.1 Ohm ESR, similar size tantalun will have 1 ish Ohm. Look up "snubber". Also, look up the voltage dependence of the ceramic capacitor and the electrolyte.

[janekm]

Also you can get SMD versions of electrolytic caps.

[mariush]

There's also surface mount polymer capacitors ..

example polymer-aluminum : https://na.industrial.panasonic.com/products/capacitors/polymer-capacitors/sp-cap-polymer-aluminum  or polymer-tantalum : https://na.industrial.panasonic.com/products/capacitors/polymer-capacitors/poscap-tantalum-polymer