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ISO7841: Signal problems

Part Number: ISO7841


We are using the ISO7841 for SPI communication isolation with external sensors. The SPI speed is 4Mhz.
The traces from the MCU to the isolator and from the isolator to the sensor (connector and electronics) are intact

We have a problem that the signal that is coming from the MCU ( SPI - SCL and MOSI ) can not be seen on the other side of the isolator. On the other side only 3V can be seen everitime.

What can be giving this problem ?




  • Hi Robert,

    Thanks for asking your question on E2E.

    The ISO7841 default output state is high (the ISO7841F default state is low) and so I would first check the input power (Vcc1) of the ISO7841. If input power is lost or the signal is lost the ISO7841 will output high. Assuming your Vcc2 is 3V, this may be what you are seeing. 

    If power on the input side is good I would then check the signals at the pins of the ISO7841 to double check that the device is seeing the signals it should. 

    If neither of those work, now might be a good time to do a schematic review. You can post your schematic here on the forum and our team will review it. If you are not comfortable sharing your schematic on the public forum we can arrange to share it privately via E2E messages or email. 

    Best regards, 


  • In reply to Dan Kisling:

    Hi Robert,

    I have not heard from you in about a week. I'm going to assume that you were able to figure out why you were not able to see signals on one side of the isolator. If this is not the case please respond to this thread or start a new one and I will be happy to support you further.

    Best regards,