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ISOW7840: for Applied Part CF

Part Number: ISOW7840
Other Parts Discussed in Thread: ADS1298R,

hi,

can i use ISOW7840DWER for Medical ECG devices to achieve the Type CF Applied at the AFE input side of ADS1298R.

WITH regards,

Ashok KR, 

  • Hi Ashok,

    Thank you for your interest in ISOW7840. I am not familiar with Type CF input that is being applied at the AFE input of ADS1298R. You can certainly use ISOW7840 to isolate ADS1298R from rest of the system by interfacing it in between ADS & MCU SPI ports. Please do consider ISOW7840 VISO voltage output ripple into account while designing your system. If the ripple is acceptable to ADS1298R then there is no concern but if it is on the higher side then you can use an LDO to improve ripple output and then apply it to ADS and/or rest of the components.

    I hope that answers your question, thank you.


    Regards,
    Koteshwar Rao
  • Hi Koteshwar Rao,

    Thanks for the responce.

    how about the leakage current of the ISOW7840. since my system demanding low leakage current of less than 10uAmps.


    Regards,
    Ashok KR
  • Hi Ashok,

    Can you please elaborate on your question? Which leakage current are you referring here?
    Are you referring to leakage current of the isolation barrier? Typically we expect the leakage current through isolation barrier to be less than 1pA.

    If this doesn't answer your question, please do help me understand your question better. Thanks.


    Regards,
    Koteshwar Rao
  • Hi Koteshwar Rao,

    Since i am planning to use this device for the isolation at the AFE ADS1298R and also want to ensure the leakage current should be low. But when comes to Isolation Barrier leakage current as you said 1pA looks impressive.

    if we see the DC/DC converter of medical Grade (MINMAX MIW03M ) the cost was more ( since the Isolation Capacitance was less) like yours. so i want to know whether this ISOW7840 can meet the IEC60601-1 under type CF (Low leakage Current 10uA) category or not.



    Regards,
    Ashok KR.
  • Hi Ashok,

    Thank you for your inputs.
    I looked at the MINMAX MIW03M IEC 60601-1 certificate and I see it claims that select MINMAX devices conform to IEC 60601-1. Similarly, you can notice that ISOW7840 datasheet also mentions that the device conforms to the medical end equipment standard IEC 60601-1 Ed.3.

    Regarding the leakage current, I wanted to make sure I understand the correct definition of the leakage current in reference to IEC 60601-1 and hence was seeking for more information in this regard. When I looked through the IEC 60601-1 Ed.3 standard, I understand that leakage current is defined as the current passing through Type CF inputs (patient side) to Protective Earth (PE) through the isolation barrier.

    I am assuming that the leakage current you are referring to is in reference to the current passing through from Type CF input to ADS1298R, then to ISOW7840's isolation and then to PE. If my understanding is correct, then this leakage current passing through ISOW7840 from any pin on Side1 to any pin Side2 would be typically less than 1pA at room temperature. When temperature and other process variations are accounted, the worst case leakage current through ISOW7840 can be upto 1nA.

    Let me know if this answers your questions, thank you.


    Regards,
    Koteshwar Roa

  • Hi Koteshwar Rao,

    Thanks for that. In this case, i need to validate it in the house before going for compliances.



    with regards,
    Ashok KR,
  • Hi Ashok,

    Sure, please do validate the leakage current of isolator and please do help us with your results once you were able to complete the validation. If there are any issues, please feel free reply to this E2E post or create a new one. Thank you.


    Regards,
    Koteshwar Rao