low esr caps.......

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wendell

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Joined 2004
#1
What to look for in a low esr caps? i'm looking at panasonic fc from digikey , what do the following mean and how do they determine how the caps performance? I know that there are probably other caps out there like blckgates and rubycons but are pricier.

I have 3 project going on at the moment and I'm not looking to break the bank with the components unless i really need to,


1 leakage current,

2 Impendence

3 ripple current


do I look for high or low numbers for each one?



Thanks
 
#2
wendell said:
What to look for in a low esr caps? i'm looking at panasonic fc from digikey , what do the following mean and how do they determine how the caps performance? I know that there are probably other caps out there like blckgates and rubycons but are pricier.

I have 3 project going on at the moment and I'm not looking to break the bank with the components unless i really need to,


1 leakage current,

2 Impendence

3 ripple current


do I look for high or low numbers for each one?



Thanks
Click to expand...


1. low

2. low

3. high
 
#3
Hi, Caps designed for switch mode PSU usually low impedance. This is linked to a low E.S.R. or equivalent series resistance. These are well suited for use where the ripple component is of high frequency. These often have 105 degree temperature rating as well. Leakage current is not an issue with any modern electrolytic. Ripple current is the amount of allowable current the capacitor can pass without overheating and is usually measured at 100hz or so. High ripple current is important for main smoothing caps in high current powersupplies. All electroylitics exhibit a rise in inductance with increasing frequency and this limits their effectiveness anyway, it is beneficial to add a small 0.1mfd cap across cap to counter this.
Regards Karl
 
#6
There's no yes or no answer to that one 🙂 The low ESR cap is better able to decouple at HF. If it helps reduce noise on a rail that is beneficial, but it does not neccesarily mean the improvement is audible. Each and every capacitor has to be chosen according to it's function. Low ESR caps for example often have lower ripple current ratings at mains frequency (50/60hz) so are less well suited to some linear power supply applications. If you want a decoupling cap for a SMPSU running at 100khz you would be looking at a low ESR type, possibly with further bypassing with a small 0.1 or similar. There's no one size fits all.
Regards Karl
 
#7
Hi,

This is for an output cap to the speakers, right? Panasonic has great caps. There's a thread by P-A here that proves that.

The Digikey catalog shows the ripple handling current at various frequencies. What I would do is look for the one with the highest ripple handling current at 60 or 120Hz and get that. Then bridge the terminals with a 1 or 2.2uF polyester cap in the circuit.

And IMO, after repeated testing in this area, a generic Rubycon will smoke a Blackgate - the only thing the Blackgate smokes is your wallet :clown:

Cheers!
 
#8
FC and FM are the good lines from Panasonic for medium-sized capacitances at medium voltages. FK is also very good but is SMT. All are low ESR.

Low ESR electrolytics will provide good bypassing up until about 1MHz. Above 1MHz you need to use film or ceramics.
 
#13
why does Farnell only stock low voltage caps for low impedance/ high capacitance ZLx series caps? if they're going to be used for power supplies wouldn't >50V be nice?
Click to expand...

Remember, the ZL/ZLH series are used for the output side of SMPS where voltages of 12,5 and 3.3v are typical. If you want something for smoothing a linear supply then look at the Panasonic FC/FM series.
 
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