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ISO7740: Glitch free at power on / off

Part Number: ISO7740
Other Parts Discussed in Thread: ISO7440

Hi,expart.

Please teach me.
ISO7xxx is a capacitive isolating.
ADI is a magnetic isolating.

When comparing the capacitive method and the magnetic method, which is superior in the following spec?

"Glitch free at power on / off"

and
please tell me also the reason for your thoughts.

Best regards.
Ryuji

  • The isolation method has nothing to do with that. A device is glitch free only if it has additional circuitry to implement that.

    The ISO7440 datasheet says in footnote 3 of table 2 that "the outputs are in undetermined state when 1.7 V < VCCI, VCCO < 2.25 V", so it is not glitch free.

  • Hi Ryuji,

    This would actually depend on how the system is designed.

    Could you please clarify how the power up sequence is done? Are both sides of the isolator being powered up together or the output side is powered up after the input side is completely powered up and stable?
    Could you also share the bias condition of the input pin? Is it connected to VCC/GND or is a signal already being applied when the power up is being done?

    Regards,
    Anand Reghunathan