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ISO7710-Q1: output impedance

meran_ruru
Prodigy 40 points
Part Number: ISO7710-Q1

Tool/software:

The output of ISO7710-Q1 is used as the EN signal for the IC. From the viewpoint of noise rejection, 0.22uF is added to the output node of the isolator as a C filter.
At this time, the rise waveform of the HIGH signal is slow, and we believe that this is related to the output impedance of the isolator. I would like to know if there is any page that describes the output impedance.

  • 0
    TI__Genius 9825 points

    Hello,

    Thank you for your question.

    I understand that you would like to have better noise rejection. However, I would still need some more information to get a better idea of the issue.

    Can you please share your schematic of the isolator? If you have waveforms, that would also be very helpful.

    Regards,
    Aaditya Vittal

  • 0 in reply to Aaditya Vittal
    Prodigy 40 points

    We apologize for the lack of information.
    The circuit diagram and waveforms during measurement are shown below.

    Also, the output impedance measured with a source measure and multimeter was about 51Ω.

    Thank you for your continued support.

  • +1 in reply to meran_ruru
    Guru 276380 points

    From the VOH specification: 0.2 V / 4 mA = 50 Ω. So you'd have a low-pass filter with a time constant of about 50 Ω × 0.22 µF = 11 µs.

    Please note that the 50 Ω value applies only for low currents; at higher currents, the output transistor saturates, and the impedance is higher.