High Ripple Current and Low ESR

[Braegnok]

Hello, I have a question about Polymer Capacitors used in motherboards.
When comparing polymer capacitors datasheets, And all items listed are the same, except for the Ripple Current and Equivalent Series Resistance.
Are the capacitors with higher ripple current and lower ESR, better grade?
Example: Ripple Current 6A and ESR 5 mOhm
VS: Ripple Current 5A and ESR 8 mOhm
Which of the two polymer capacitors would be considered higher quality, or better grade?... And what does the (Series) refer to, does this need to match also or are there better series then others?
Thanks in advance for any replies.

[Braegnok]

Re: High Ripple Current and Low ESR

Hello, I have a question about Polymer Capacitors used in motherboards.
When comparing polymer capacitors datasheets, And all items listed are the same, except for the Ripple Current and Equivalent Series Resistance.
Are the capacitors with higher ripple current and lower ESR, better grade?
Example: Ripple Current 6A and ESR 5 mOhm
VS: Ripple Current 5A and ESR 8 mOhm
Which of the two polymer capacitors would be considered higher quality, or better grade?... And what does the (Series) refer to, does this need to match also or are there better series then others?
Thanks in advance for any replies.

OK, I think I'm starting to catch on.
Lower ESR = Good
High Ripple is prefered,... and Series is Chip type or Lead type.

[mariushm]

Re: High Ripple Current and Low ESR

ESR is equivalent series resistance... key word is resistance ... a resistance blocks the current flow which is bad.
So more resistance is bad, as it heats up the internals of the capacitor... lower esr is better.
But up to a point, it really depends on the circuit the capacitor is in - some circuits DEPEND on the capacitor having a bit of resistance which is used by the circuit or IC for various reasons.
Some circuits like the voltage regulator of the cpu needs as low esr as possible, something like a linear regulator may need low esr but are unstable if that esr value is below a specific value, for example 20 mOhm.
That's why most people here will recommend replacing capacitors with capacitors that have the esr value as close as possible to the old capacitor's value.

Ripple is an "up to" value, just like the voltage rating. Capacitor with 16v rating will work with any voltage up to 16v. Just the same, the capacitor will tolerate ripple up to that many mA.

More ripple handling capability is better, but that's usually related to the shape of capacitor (diameter, height, and voltage rating) and not last, the type of materials used (polymer caps can handle more ripple than regular electrolytics)

[PeteS in CA]

Re: High Ripple Current and Low ESR

Slight clarification. Any regulator - linear or switching - has one or more components that compensate for the ESR of the O/P capacitor. There is some tolerance in that, so the match doesn't have to be perfect, just in the right area in the ballpark. Mobo regulators happen to need the very lowest ESR possible when designed, and the regulator is compensated for that ESR. P/S regulators, being somewhat distant from the Mobo don't need the absolute best ESR, so it is possible to pick a cap that is too good and by so doing cause a loop stability problem (oscillation).

But in pure qualitative terms: the lower the impedance (of which ESR is a part) the better; the higher the ripple current rating the better (as mariushm posted).

[Braegnok]

Re: High Ripple Current and Low ESR

Thanks You guys, I have learned a lot in 3 days. Since damaging one of my capacitors and looking for a correct replacement, I had no clue how important they are in a computer. Or how they work, but it's great fun learning something useful, that can save you money or improve your stability while overclocking or building a rig using a old used motherboard.
Thanks for all the help!!..