6 Replies Latest reply on Oct 6, 2015 4:07 AM by user_246598725

    PSOC5LP  VDDIO collapsing

    user_362856198

      Hello Community,

         

       

         

      Before I make the experiment, maybe somebody already has an idea about this.

         

      I'm designing an board where a PSOC5LP will be the power monitor/controller and it will also control some of the onboard ICs through SPI I2C etc etc.

         

      Some of those ICs will be a on a power domain that can collapse or just be disabled by the PSOC it self (with all the precautions of this scenario), which will also collapse one of the VDDIO domains, where the ICs will interface the  PSOC.

         

      Will this affect proper operation on the rest of the chip? Will the PSOC power domain be robust to such scenario? I'm wandering if some ESD protection will allow some current coming from other internal power rails.

         

      I could not find any information regarding this... My next step will be experimentation :) 

         

      Any help will be welcome,

         

      Thanks, Marco

        • 1. Re: PSOC5LP  VDDIO collapsing
          user_14586677

          The principal concern is that no signal connected to PSOC can exceed

             

          its power rails. So as long as no transient occurs that tries to take a

             

          pin below Vssd or > Vddd you should be OK. Of course the code base

             

          has to handle an interface that is no longer meeting specs. You may want

             

          to detect in HW and code that the interface is no longer powered properly.

             

           

             

          You also have to be concerned about brownout types of failure, eg. if you

             

          have an externally generated logic signal that is connected to a PSOC input

             

          pin that it does not "hang" around the threshold point of the CMOS input and

             

          initiate large currents thru the totem pole input structure of CMOS. One more

             

          reason that PSOC, if it detects low power to external circuits, should shut off

             

          completely the external circuits, eg. controlling a power MOSFET to gate

             

          power on and off.

             

           

             

          Regards, Dana.

          • 2. Re: PSOC5LP  VDDIO collapsing
            user_362856198

            Hey, thanks for the quick answer.

               

            What about the collapsing of one of PSOC VDDIO rails itself? Would the PSOC continue to work if no other rails collapse? Would a brownout condition be generated for one particular VDDIO section?

               

            Best regards,

               

            Marco

            • 3. Re: PSOC5LP  VDDIO collapsing
              user_14586677

              What about the collapsing of one of PSOC VDDIO rails itself? Would the PSOC continue to

                 

              work if no other rails collapse?

                 

               

                 

              Yes it will work fine if you take a Vddio to 0 V, obviously that port becomes non functional

                 

              for Data I/O.

                 

               

                 

              Would a brownout condition be generated for one particular VDDIO section?

                 

               

                 

              You have to do the detection circuit/code to handle the fault on an I/O port, the PSOC does not look

                 

              at Vddio to test brownout, it looks at Vddd and Vdda.

                 

               

                 

              Regards, Dana.

              • 4. Re: PSOC5LP  VDDIO collapsing
                user_362856198

                Good directions,

                   

                Thanks,

                   

                Marco

                • 5. Re: PSOC5LP  VDDIO collapsing
                  user_14586677

                  Glad to have been helpful.

                     

                   

                     

                  Regards, Dana.

                  • 6. Re: PSOC5LP  VDDIO collapsing
                    user_246598725

                    Hi Marco,

                       

                     

                       

                    just one additional note: if I remember correctly, port P12 is specially designed for hot-plugging etc. Maybe this will help you in your design.

                       

                     

                       

                    Regards,

                       

                     

                       

                    Ralf