9 Replies Latest reply on Dec 30, 2018 1:38 AM by alamandaa_16

    I/O Power rail input, Outputing voltage ?! 2.6V on my 1V8 rail



      I have an FX3 which is as follows:

      VIO1 is 1V8

      VIO2 is 1V8

      VIO3 is VADJ

      VIO4 is 1V8

      VIO5 is VADJ

      AVDD is 1V2

      VDD is 1V2

      U3TXVDDQ is 1V2

      U3RXVDDQ is 1V2

      CVDDQ is 1V8

      U3VSSQ is GND

      VBATT is connected to VBUS


      When VADJ is connected to 1V8, everything is hunky-dory. But when VADJ is connected to 2V5, my 1V8 rail for VIO1, VIO2, VIO4 and CVDDQ is shifted up to 2V6.

      I don't have any conflict between 1V8 and 2V5 I/O. And the fact that is raised above 2V5 means it is most likely from the 5V or the internally generated 3V3.


      Does my power rail combination not possible, they are normally between the limits express in the datasheet.


      Any help is welcome. Thanks.