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ISO1540: spec check

Part Number: ISO1540

Hi Sirs,

Sorry to bother you.

We use ISO1540 and we found the waveform is be inverted from the original waveform

(CH1: I2C_SCL_S0, CH2: I2C_PSE_CLK_IC)

We saw over shoot & under shoot on channel 2

Is it normal?

  • Hi Shu-Cheng,

    Thanks for sharing the waveform and schematic for better understanding of the issue.

    I see you have mentioned that the output is inverted from the input signal in your post but I do not see any such inversion in the waveform. I am assuming the inversion is not the issue and the issue is the noise seen on the output waveform. Could you please confirm this?

    I am not very sure where this noise is coming from, ISO1540 doesn't produce such noise. It is possible that the power supply +V3.3_PSE is noisy or the PCB layout is not optimum which is leading to noise coupling from other circuit on the same or nighbouring PCB. Please do share +V3.3_PSE waveform and customer PCB layout to check if there is any issue in them.

    I also noticed that there are no pull-up resistors listed on I2C_SDA_S0 and I2C_SDA_S0 pins, I am assuming the pull-up resistors are not visible in this schematic but are present in rest of schematic which is not shown here. Thanks.

    Regards,

    Koteshwar Rao

  • Hi Shu-Cheng,

    Please do share us your inputs or let us know the update on the issue so that we can help you address this issue. Thanks.

    Regards,

    Koteshwar Rao

  • Hi Sirs,

    The oscilloscope will short the ISO GND to the digital GND

    Remove digital GND, ISO1540 waveform is normal

    Thanks for your help.