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isoSPI in a common ground system

Category: Hardware
Product Number: LTC6820
Software Version: N/A


Thanks for your reply in advance.

Can I use isoSPI LTC6820 in a common ground system? How can I immune it better against EMI noise in a common ground system? The system voltage is less than 5V. It is a small device, battery-powered. The SPI is running at 300KHz.

Best regards,


  • Yes, isoSPI will work even if both ends of the link share a common ground.  You don't need to configure it any differently than if it were on a link that did need isolation.

    That being said if you have a common ground the only benefit to isoSPI over SPI is longer cable length and improved EMC performance.  With a common ground and short bus length you're often better off just using standard 4 wire SPI.

  • Thanks for your reply.

    We have a shortage of space. Can I connect the master and slave directly without an insolation barrier and only use a CMF?

    If the insulation barrier is required, can I use a capacitor and maintain the full functionality under the EMI test (in this case, the pull-up resistors cannot be higher than 100Kohm as our system is low power)?

    The signal barrier is less than 1m, and the EMI criteria is 3v/m performance.

    Thanks in advance for your reply.