Effects of High ESR

[capamatic]

Hi,
My electronics background is fairly good, but I wonder if you can clarify something for me.
A failing electrolytic capacitor will cause operational failure, complete or partial, in its particular circuit. In relation to a capacitor whose ESR is too great, how exactly will this increased resistance cause failure of the circuit. It clearly will limit the current, but what effect would this have on the circuit. Is the reduced current the primary reason for circuit failure ? What other effects will high ESR have ?
Many thanks.

[linuxguru]

Re: Effects of High ESR

In a PSU/VRM, it will probably increase the ripple voltage, causing the peaks to go dangerously high and causing circuits that depend on regulated voltage to fail. This is most commonly seen with CPUs, Northbridges and Hard drives.

[PeteS in CA]

Re: Effects of High ESR

Another effect will be that the voltage will dip out of regulation with a large, fast increase in load. You get a large (I)(R) drop when the current is coming from the cap(s) and the regulator hasn't yet responded.

[gonzo0815]

Re: Effects of High ESR

...and then the regulator will overshoot. Another concern is, that the caps will getting hot as the high currents flowing over it. Thus it degrade faster.
In most cases, the ripple will just makes the singals diminishing into noise, wich makes the system slower if it can correct transmision data, or it will running foobar if the signals are too distorted.

[bgavin]

Re: Effects of High ESR

Here is a good PSU article on ESR and the Intel VRM spec