2 Replies Latest reply on Feb 12, 2015 2:36 PM by user_14586677

    4 IDacs but only 2 dedicated pins ?

    user_347933176

      What am I missing ? I need a PSOC 3 or 5LP with 4x IDac 2mA range.

         

      The knowledgebase article "Use of dedicated IDAC pins (12/24/2011)" says "Each IDac in PSOC 3/5 has a dedicated output pin". Using the Device Selector I see how many IDACs each component has so I choose CY8C3866LTI-067 (QFN-48 package). 

         

      But this processor only has 2 IDAC:HI outputs (P0[6] and P0[7]). It has no P3 port so I assume I can only use 2 high-current IDAC outputs. 

         

      Is this correct ? How can I get an overview of controllers having 4 high-current outputs ? By looking at the number of pins ?

         

      Thanks

         

      Patrick

        • 1. Re: 4 IDacs but only 2 dedicated pins ?
          user_78878863

          When you look at the CY8C38 family data sheet, you can find the pinouts for the different packages. From there you can see that only the 68 and 100 pin packages have 4 dedicated IDAC output pins.

          • 2. Re: 4 IDacs but only 2 dedicated pins ?
            user_14586677

            The datasheet says the dedicated pins "should" be used on high current

               

            range. I would posit this is because of a compliance range issue keeping

               

            the IDAC in constant I mode. What you could do is using the analog view,

               

            ohmeter, look at a route to a low R path and try it again to a "normal" GPIO

               

            and get an idea of difference in path.

               

             

               

            Note Rdson onchip of a mux, path, has wide variation, and no specs to guide

               

            you on this. My point would be that if your "load" is anything but a virtual ground

               

            a less desired route would have significant impact on compliance in addition

               

            to inherent IDAC architecture contribution.

               

             

               

            You could do some trial testing/testbed on compliance issue to see how much

               

            margin there is before IDAC is pulled out of compliance

               

             

               

            Just a thought.

               

             

               

            Regards, Dana.