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What is a "Super Cap" — Parallax Forums

What is a "Super Cap"

KatyBriKatyBri Posts: 171
edited 2006-11-22 11:45 in General Discussion
Some IC's, such as the DS1302 time keeping chip, call for a "super cap" for battery backup. What does "super cap" mean? Thanks.

Comments

  • BenoitBenoit Posts: 47
    edited 2006-11-21 05:00
    KatyBri,

    A super cap is simply a capacitor that has a large "capacity", in the order of 1 or more farads. A search on google will return a few of these.
    You can find them on eBay as well.

    -Ben
  • KatyBriKatyBri Posts: 171
    edited 2006-11-22 00:36
    Ben-

    If you use large value caps "super caps", I would expect the resting voltage on these caps could get pretty high. Do you have to worry about this voltage exceeding the max allowable voltage of the IC pin it is attached to?
  • tperkinstperkins Posts: 98
    edited 2006-11-22 01:16
    Hello folks,

    The voltage of a cap will never be higher than the highest voltage of the bus the cap is on, at least in a super cap battery backup replacement application. If you have good regulation when powered, it should be a non-issue.

    Yours, Tom P
  • tperkinstperkins Posts: 98
    edited 2006-11-22 01:25
    PS. Of course, the quantity of power in the cap could mean it could really fry a component failing in a conductive state, but that's amperage, not voltage. Yours, TDP
  • PJAllenPJAllen Banned Posts: 5,065
    edited 2006-11-22 02:45
    There's a fine line between batteries and capacitors.· You can think of a capacitor as a battery that doesn't hold a charge for very long, but charges much·quicker than a battery; or a battery as being a capacitor that holds a charge for a long time indeed.· There are similarities in the construction of electrolytics and batteries, too.
  • BenoitBenoit Posts: 47
    edited 2006-11-22 04:29
    I believe that capacitors keep their charge for a long time. I haven't tested it, though. I could always open that old TV and see if the caps still hold charges [noparse]:)[/noparse]

    KatyBri, the capacitor will hold the voltage at the level you charged it...
  • tperkinstperkins Posts: 98
    edited 2006-11-22 11:22
    couch-pilot, please keep one hand in a back pocket...

    ...just to make sure you can tell us about it. ;^)

    Yours, TDP
  • PJAllenPJAllen Banned Posts: 5,065
    edited 2006-11-22 11:45
    It's times like these where a line from Kipling's "If" comes to mind.· But, anyway, a·capacitor's (or a super cap's) charge doesn't have anywhere near the shelf life of a battery's... 'nuff said.
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