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  1. #1
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    Reverse ESD Discharge control

    Hi,

    I have a design which is suffering from ESD related issues. The design runs off both a lithium battery and a 14v DC supply and uses a simple Diode O-Ring type setup to switch between the two power sources.
    It has ESD protection consisting of ESD / TVS diodes, on all external IO’s (HDMI, USB, etc etc) as well as an RC circuit were applicable. All the electronics are housed in a plastic moulded case.

    When an ESD pulse is sent from the outside to the device we have no issues. However, when the plastic case housing the electronics is energised while running off the battery, (by say rubbing it on the carpet) and the discharge runs from the case or DC input jack to a metal object we have hardware crash inside.

    Has anyone had any experience with this ¬ďreverse¬Ē ESD type of discharge ?

    Thanks for any help,
    Jeff

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    Re: Reverse ESD Discharge control

    Hi,

    ESD protection ... but still ESD problems....
    Thus I assume you did something wrong.

    We don't know what you did, unless you show us.

    Klaus
    Please donīt contact me via PM, because there is no time to respond to them. No friend requests. Thank you.



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    Re: Reverse ESD Discharge control

    First make sure that you don't have any unconnected inputs.
    Next check for sensitive high-impedande nodes.

    It it difficult to give more advice without some documentation.



  4. #4
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    Re: Reverse ESD Discharge control

    ESD is ESD, it can be either polarity of voltage /
    direction of current.

    A better choice of case materials might help.

    All of that clamping may (?) prevent damage-level
    ESD but it will surely not keep inputs or outputs from
    being driven to the rails and slightly beyond. A powered
    circuit could be induced to latch up, or a spurious logic
    signal interpreted causing some sort of functional
    interrupt.



  5. #5
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    Re: Reverse ESD Discharge control

    Sometime you have to use plastic for the cases, plenty of electronics in un-shielded plastic cases that work and work even if there is a ESD incident...
    Layout is critical, the position of the protection is critical... But every design has its own intricacies, so for a more focued answer we need more information.



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