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ISOW7841: Switching ISOW7841 on/off

Phil2010
Expert 4355 points
Part Number: ISOW7841

Hi,

a customer of mine plans to use ISOW7841 to isolate a RS-485 interface. To optimize operation and EMI behavior, customer follows the recommendations provided in the low-emissions application report:

Customer is concerned about the overall current consumption. They plan to switch ISOW7841 off when the interface is not used.

What do they need to consider when cutting VCC supply? The corresponding MOSFET will leave decoupling capacitors connected to VCC.

Do they need to open the input signals as well? Looking at the Abs Max specification in the datasheet, I assume that these need to be either tied low or floating/disconnected from a driver.

VCC will be 5V.

Thanks and best regards,
Phil

  • 0
    TI__Mastermind 49445 points
    Hi Phil,

    Your understanding is accurate on the approach to be followed for disconnecting ISOW7841.

    The decoupling capacitors should stay to the ISOW side if you are using a load switch between MCU and ISOW. Like you pointed out, the I/Os are to be either GNDed or left floating (either tri-stated or disconnected externally) so that the abs max specs of I/Os of ISOW are not violated.

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


    Regards,
    Koteshwar Rao