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Multiple capacitors

ArchiverArchiver Posts: 46,084
edited 2003-06-08 21:16 in General Discussion
I am using a circuit that has a voltage regulator (7805) and the maxim
7819 display controller. Circuits I've seen for each include a 10uF and
a .1uF capacitor between the power and the ground. Should I include two
of each of these capactitors (one for each) in my system or are they
duplicates and I need only one of each?

Thanks

Bob roan

Comments

  • ArchiverArchiver Posts: 46,084
    edited 2003-06-08 20:24
    In a message dated 6/8/2003 3:22:17 PM Eastern Standard Time,
    bob@t... writes:


    > I am using a circuit that has a voltage regulator (7805) and the maxim
    > 7819 display controller. Circuits I've seen for each include a 10uF and
    > a .1uF capacitor between the power and the ground. Should I include two
    > of each of these capactitors (one for each) in my system or are they
    > duplicates and I need only one of each?
    >
    >

    Use both and locate as close to the chips as possible.

    Sid


    [noparse][[/noparse]Non-text portions of this message have been removed]
  • ArchiverArchiver Posts: 46,084
    edited 2003-06-08 21:16
    The 10 uF cap near the 7805 is for charge storage to
    support its voltage regulation duties.

    The .1 uF cap near the 7805 is to supply current
    for high-frequency (short duration) switching
    spikes.

    The 7819 controls LOTS of LED's, with an internal
    scan. Normally, with a large TTL compatible
    device (RAMS, 8255's, 74HCT595's) I'd put a
    .1 uF across +5 and GND for small switching
    transients. The 7819 does lots of current,
    so the 10 uF makes sense near it. Again, you'll
    want the .1 uF also, to filter high-frequency.

    So yes, you want both, at both places.
    While this 'looks like' duplicates,
    what you're trying to do is reduce the amount
    of noise and voltage-bounce near your high
    current chips.


    --- In basicstamps@yahoogroups.com, "Bob Roan" <bob@t...> wrote:
    >
    > I am using a circuit that has a voltage regulator (7805) and the
    maxim
    > 7819 display controller. Circuits I've seen for each include a
    10uF and
    > a .1uF capacitor between the power and the ground. Should I
    include two
    > of each of these capactitors (one for each) in my system or are they
    > duplicates and I need only one of each?
    >
    > Thanks
    >
    > Bob roan
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