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Hot swap connector interface (hot plug, live insertion)

Discussion in 'Electronic Design' started by bruj02, Apr 5, 2007.

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  1. bruj02

    bruj02 Guest

    Most of the application notes and schematics about hot swap
    capabilities are geared towards the insertion of a daughter card into
    a backplane.

    I am wondering if the same principles also apply to lower power
    peripherals. Are staggered pins (longer ground pins) such as the ones
    found on a USB connector absolutely necessary?

    For example, I have always connected peripherals to the parallel port
    of my PC without worrying about blowing digital outputs or inputs, and
    have never heard about anyone damaging a printer this way.

    Is it possible to design a hot swap interface without a specialized
    connector? If so, is there a specific logic family that is more robust
    for such an application?
     
  2. Rich Grise

    Rich Grise Guest

    I'd recommend against hot-plugging anything into a printer port - in
    days of yore, you could swap out a printer adapter for about $5.00;
    these days, you blow out the mother board (at least the printer port
    part).

    Otherwise, then I'd use not only longer ground pins, but longer power
    pins, i.e. 3 lengths ground the longest, power mid-size, then signals.

    Or, better yet, design your circuit robustly enough to handle
    anything/everything that can go wrong.

    Good Luck!
    Rich
     
  3. whit3rd

    whit3rd Guest

    Well, it isn't possible without a connector. What constitutes
    'specialized' is often a matter of don't-plug-the-wrong-thing-in-here.

    Some logic (MC1489A receiver and MC1488 transmitter) is designed for
    noisy transient-filled signal wiring, and speed usually suffers
    when you use that kind of interface.

    Use of a coupling transformer (which can insulate and limit
    power transfer by saturating) can allow high speed and
    good rejection of static and transients, but requires modulation
    and demodulation. That's how Ethernet 10baseT/100baseT/1000baseT
    works. Usually you lose DC sensitivity; it was possible to
    add DC power to Ethernet, but it wasn't easy.

    The reason your printer-connect example works is the third-prong
    power pin, which grounds both the printer and computer to your
    wall socket before any data connectors are mated. SCSI is similarly
    usually capable of hot-plugging.
     
  4. Robert Baer

    Robert Baer Guest

    Of koarse it is posyball and sympal!
    Circuitry would sense the connection and then do sequential powering.
     
  5. Robert Baer

    Robert Baer Guest

    ....everything?
    Earthquakes?
    Tornadoes?
    Flowing lava?
    Floods?
    etc?
     
  6. bruj02

    bruj02 Guest

    Thanks for all the feedback. Very insightful.
     
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