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FMC V1 Power

Former Member

Hi,

   FMC V1 - PCIe power question.

  Is it ok to have the main power supply (via J14) connected when the board is installed in a PC.

 Both J14 and the PCIe connector will be providing a 12V supply. 

 D22/23 seem to provide isolation but I'm just being

super cautious.

Regards,

   Elwyn

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  • 0

    Hi Elwyn,

    Yes, the diodes will protect the inputs from backfeeding.  I would caution though that if one supply is on and the other is not, there is the potential that reverse currents could start to charge up devices connected to that rail on the unpowered side (I'm thinking on the PCIe side if the adapter is plugged in).  While the diodes are there to protect the inputs, like any other electrical protection device I'd recommend not using it if you don't need to.  The system will be most reliable if you only connect one.  If both are powered then the diodes only steer current from the higher potential, but if one is unpowered, again there is the potential for charging up the unpowered rail through leakage and reverse current paths.

    Thanks

    Chris

  • 0 in reply to ctammann

    Hi Chris,

      Thanks for the reply.

      We have an issue where our design sometimes prevents the boot up of the  PC that houses our PicoZed FMC V1.

      The design is constant but we have been playing with some constraints. Design used he Xilinx PCIe IP as the Host IF. 

       Even though Vivado runs clean with both sets of constraints - the build with one set of constraints prevents the PC from booting.

       We were thinking this could be down to the FMC drawing too much power? And were looking at potential solutions.

    Regards,

       Elwyn

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  • 0 in reply to ctammann

    Hi Chris,

      Thanks for the reply.

      We have an issue where our design sometimes prevents the boot up of the  PC that houses our PicoZed FMC V1.

      The design is constant but we have been playing with some constraints. Design used he Xilinx PCIe IP as the Host IF. 

       Even though Vivado runs clean with both sets of constraints - the build with one set of constraints prevents the PC from booting.

       We were thinking this could be down to the FMC drawing too much power? And were looking at potential solutions.

    Regards,

       Elwyn

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