ESD not working

Discussion in 'Cadence' started by bhargavalluri, Nov 13, 2006.

  1. Hi,

    I am trying to simulate a simple ESD ciruit( containing 2 diodes) using
    cadence spectre, but my circuit is not functioning as expected.
    Whatever voltage i give at the input is coming out to the output. Can
    anyone tell me what can be the reason for this behavior and how i can
    overcome it.

    Thanks,
    Alluri.
     
    bhargavalluri, Nov 13, 2006
    #1
  2. bhargavalluri

    linkin Guest

    Exactly what kind of ESD functionality do you want?

    For example, an analog ESD circuit might have a diode from VDD to the
    input, and another diode from the input to GND. Both diodes nominally
    will be reverse-biased, and it is actually desirable that your output
    voltage is equal to the input voltage (they are actually the same node
    in this case). Ideally you don't want the presence of ESD diodes to
    impact the performance of the signal during normal operation.
     
    linkin, Nov 13, 2006
    #2
  3. Let me explain the situation better, I have two diodes as you said, a
    diode from vdd to input and another from input to gnd. my vdd is 1.8 v
    , and my input voltage swings from 0v to 5v. When my input is at 5v the
    diode which is connected to vdd should turn ON and my output should be
    1.8 v,but i am getting same 5v at output. I have tried many things like
    connecting a resistor at the output and taking output from that
    resistor, but nothing seems to work.
     
    bhargavalluri, Nov 14, 2006
    #3
  4. bhargavalluri

    linkin Guest

    Does your input voltage source have some source resistance?
     
    linkin, Nov 14, 2006
    #4
  5. NO,my input voltage source doesnt have any resistance and i also have a
    resister at the output to compensate for any forward resistance the
    diode might have.
     
    bhargavalluri, Nov 15, 2006
    #5
  6. bhargavalluri

    Poojan Wagh Guest

    If your input voltage source is directly tied to your input, and it has
    no source resistance, how can the voltage on your input be anything
    other than 5 V? As a sanity check, probe the current going through the
    diode. Is it large?
     
    Poojan Wagh, Nov 15, 2006
    #6
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