Skip to main content
Visitor II
April 19, 2005
Question

recommended state of un connected IOs

  • April 19, 2005
  • 5 replies
  • 1156 views
Posted on April 19, 2005 at 06:08

recommended state of un connected IOs

    This topic has been closed for replies.

    5 replies

    adi2Author
    Visitor II
    April 17, 2005
    Posted on April 17, 2005 at 09:40

    Hi !!

    what is the recommended state of un connected ios ???

    input/ output, shall i connected it through a resistor to the gnd ?

    leave connection open ???

    Visitor II
    April 18, 2005
    Posted on April 18, 2005 at 02:01

    This is explained in datasheets in electrical section. Leaving the IOs as un-connected is not recommended. Pull-dn to gnd or pull-up to Vdd is the recommended state.

    Visitor II
    April 18, 2005
    Posted on April 18, 2005 at 09:25

    Why can't put the un-connected I/O pins in push-pull output?

    It's the un-connected floating inputs that are normally the problem.

    Visitor II
    April 18, 2005
    Posted on April 18, 2005 at 09:28

    This article has a good explanation:

    http://massmind.org/techref/logic/xtrapins.htm

    Visitor II
    April 19, 2005
    Posted on April 19, 2005 at 06:08

    Hi MD,

    you are right No problem to keep the IO in o/p PP or OD low but The problem appears if the application is used in high noise environment.If the PC is lost because of some problem or ESD, the IO may become i/p floating and cause the consumption. Even o/p if shorted accidently to any signal can cause pb.

    So, if all possibilities are evaluated, there is always an agreement on external pU/pD.