4 Replies Latest reply on Apr 20, 2014 9:58 AM by user_14586677

    GPIO Pin Vs. SIO Pin - Driving a power MOSFET

    user_37926942

      Hello All,

         

      I have been trying to drive an external power MOSFET (IRFD113 - N Channel) with the PSoC 3 at ~20 kHz. The GPIO pin appears not to have enough drive strength to switch the FET with acceptable rise/fall times. I was thinking that the SIO pins might help with their improved current sinking capabilities (20mA vs. 4mA). Does anyone have any suggestions on how I might go about doing this? Could I parallel pins for improved drive strength?

         

      Thanks,

         

      Diode Dan

         

      P.S. I am aware of external MOSFET gate driver ICs. I would love to see a clever PSoC only solution though!

        • 1. Re: GPIO Pin Vs. SIO Pin - Driving a power MOSFET
          user_78878863

          If you want to use a SIO pin, you just need to connect your MOSFET to a IO pin which supports this feature.

             

          What is the gatwe capacitance for the MOSFET you want to use? 20kHz is not such a high frequency, the PSoC might really be able to drive this directly The CY836xx series is specified, even for slow slew rate, to drive a load of 25pF up to a frequency of 7Mhz with the normal GPIOs, and up to 5MHz with a SIO. (Funny that the SIO is slower in this regard, look at the data sheet pages 76 and 79)

          • 2. Re: GPIO Pin Vs. SIO Pin - Driving a power MOSFET
            user_14586677

            The IRFD113 has 200 pF of input C and Vgson drive of 10V for Rdson rating.

               

            You sure this is device you want, or a logic level FET more appropriate ? Note

               

            in latter you typically have even more Ciss to deal with.

               

             

               

            Yes, you can parallel pins to get more drive, there is a limit for the overall port

               

            in the datasheet for allowed C.

               

             

               

            Remember to set initial state of pin to keep MOSFET off.

               

             

               

            Lastly if you need real low RDSon, and "clean" drive, consider external drivers.

               

            There are parts by many manufacturers that can drive very high C loads. Board

               

            layout critical, high C drive currents with start L give rise to some pretty big transients.

               

            Even some buffers in single gate logic families (cheap stuff, pennies) could be considered.

               

             

               

            Regards, Dana.

            • 3. Re: GPIO Pin Vs. SIO Pin - Driving a power MOSFET
              user_37926942

               Thanks for all of your answers!

                 

              I will need to drive a fairly significant amount of power, hence the power MOSFET. I have been using the EL7104 with good results (+5V supply).

                 

              Dana, you mention the use of logic level transistors. Are there any logic level transistors that can handle currents in excess of 1A (transient pulse of a SMPS, but high nonetheless).

                 

              Thanks,

                 

              Diode Dan

              • 4. Re: GPIO Pin Vs. SIO Pin - Driving a power MOSFET
                user_14586677

                Many manufacturers -

                   

                 

                       

                TI

                   

                NSC

                   

                IRF

                   

                ON

                   

                LINEAR

                   

                VISHAY

                   

                FAIRCHILD

                   

                ST

                   

                INFINEON

                   

                AVAGO

                   

                DIODES/ZETEX

                   

                .........

                   

                 

                   

                Regards, Dana.