5 Replies Latest reply on Feb 24, 2015 1:00 AM by user_418894472

    Confusion in PSoC-4 OP Amp datasheet

    user_418894472

      Pleasehelp me understand the op-amp datasheet of psoc-4

         

      The datasheet of PSoC-4 Op-Amp reads:

         

      [1] I_OUT_HI = 10mA (minimum)

         

      max and typ are not specified. What is the meaning of minimum 10mA?

         

      [2] V_OUT @ I_Load  10mA = 0.5V min and Vdda - 0.5V max

         

      What is the meaning of this? The output should not fall below 0.5V?

         

      [3] It written.... "Low resistive connections are made from the

         

      Opamp to three select pins to provide optimal performance."

         

      What's the meaning of this? Does it mean that only three pins of the GPIO can work faithfully with the op-amp? Which three pins?

        • 1. Re: Confusion in PSoC-4 OP Amp datasheet
          user_1377889

          [1] The opamp can sink or source 10mA (guaranteed) but it can be more.

             

          [2] When sinking 10mA the output voltage offset is 0.5V, when sourcing 10mA the output voltage offset is -0.5V (output is then Vdda -0.5V

             

          [3]Each of the opamp has dedicated pins, they may be used by another component when not used by an opamp. Since there are different sockets for PSoC4 easiest is to build the project that uses opamps and let the fitter choose the pins. In the pin-view the preferred use of a pin is shown.

             

           

             

          Bob

          • 2. Re: Confusion in PSoC-4 OP Amp datasheet
            user_14586677

            3) See the dedicated table chart in this ap note -

               

             

               

                

               

                     

               

            http://www.cypress.com/?rID=93401     AN86439 - PSoC® 4 - Using GPIO Pins

               

             

               

            What do you need to drive with the OpAmp, there are ways to increase current ?

               

             

               

            Regards, Dana.

            • 3. Re: Confusion in PSoC-4 OP Amp datasheet
              seg

              Bob:

                 

              Almost right. This is an output swing limit, not an offset.

                 

              2. When driving high, the opamp will meet spec when sourcing current up to an output voltage of Vdd-0.5V. It may go further at the specified load, but no guarantee. Similarly, when when sinking, the output will drive current down to an output voltage of 0.5V. Again, it may go further at the specified load, but no guarantee.

                 

              ---- Dennis

              • 4. Re: Confusion in PSoC-4 OP Amp datasheet
                user_1377889

                @Dennis,

                   

                Yes, output swing limitation. I just had a language limitation. ;-)

                   

                 

                   

                Bob

                • 5. Re: Confusion in PSoC-4 OP Amp datasheet
                  user_418894472

                    Thanks everyone for the reply!

                     

                  I need to sense three different voltages in the range of 0V-500V DC. 

                     

                  Since the interface has large value resistor dividers (200kohm/1kohm), I want to use the op-amp as a buffer to the ADC.

                     

                  Also since there are only two op-amps and three input voltages, the op-amps must be multiplexed.

                     

                  Please could you provide a rough estimation of time, as to how long must the op-amps stay in one position to stabilize its output?

                     

                  Thanks