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LM2903: LM2903 output with bench plat for Rising/Down

Part Number: LM2903

Issue Description:

My customer used LM2903 to do the AC Wave Zero cross check, the IN+ connect to the AC waveform(with 1.5V Reference), the IN- is connect to 1.5V Reference. While AC Zero cross happened, the LM2903 out produced the waveform like below figures.

LM2903 Plat issue.docx

Support Need:

   Any comments for the reason that the LM2903 output plat happened during for the zero cross happened? Any comments for the schematic design which can remove the plat?

3 Replies

  • Hi Benjamin,

    Do you have a schematic you can post? What is the range of the input AC waveform signal and is it being attenuated to stay within the common mode range of the LM2903?

    Regards,
    Jaskaran
  • Benjamin
    We are out of the office for 4th of July holiday, so our response will be a little delayed.
    Chuck
  • Hi Benjamin,

    Were you able to obtain a schematic, as requested?

    What is the P-P amplitude of the AC signal?

    Is there any series resistance in the input path?

    Is the supply 3.3V?

    Can you provide a scope-shot of both input waveforms and the output?

    Looking at the output waveform, I am guessing that the input is swinging well below ground due to the "stepped" appearance.

    These devices do not handle input voltages below the GND pin too well and this may be a artifact of a saturated substrate die with large currents.

    Regards,

    Paul Grohe

    Low Power Amplifiers and Comparators (LPAC) Applications

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