ElectroStatic Discharge - Negative does it exist?

Discussion in 'General Electronics Chat' started by engineer4535, Jun 2, 2010.

  1. engineer4535

    Thread Starter New Member

    Jun 2, 2010
    I am currently working on a progect where logic is low for -5V and high for 5V on some data channels. In other channels of the circuit where standard 5V logic is used, TI TPD4E001 has been used to protect from ESD. The basic premise is an array of diodes connecting a data channel to both a positive power supply and ground in such a way that negative voltages will drain to ground and voltages above the positive terminal will drain to the power supply.

    The full solution would be to connect the ground to a negative power supply for the +/- logic channels but one is not availiable. So my questions are....

    First, is it worth while to connect the positive terminal and leave the ground disconnected? At least to protect from positive surges.

    Second, is one polarity of ESD more common then the other? i.e. is a negative ESD pulse more common then a postative pulse?

    I would welcome any other solutions as well.
    Last edited: Jun 2, 2010
  2. Wendy


    Mar 24, 2008
    ESD can come in both polarities, the exact polarity depends on how it was generated. You could connect a back biased diode (it would need to be fast) for negative ESD.

    Have you read the AAC ebook on the subject?