11 Replies Latest reply on Jun 6, 2015 6:06 AM by user_14586677

    Current Delivered by GPIO pin at 3.3 v

    user_491123998

       I want know how much current delivered by GPIO pin ,when M8C runing at 3.2 v ?

        • 1. Re: Current Delivered by GPIO pin at 3.3 v
          user_14586677

          Look at the data sheet for the part you have choosen, there is

             

          a source (P channel output transistor) and a sink (N channel

             

          output transistor) spec for current delivered at a specific voltage.

             

          In the electrical specifications section of datasheet.

             

           

             

          Some data sheets also have curves of Iol and Ioh vs Vol and Voh.

             

           

             

          Regards, Dana.

          • 2. Re: Current Delivered by GPIO pin at 3.3 v
            user_491123998

             they mention Maximum Port pin current =50mA 

               

            they did not mention the voltage level 

               

            i want to know at 3.2 V level

               

            what is the current deliver at strong mode , High Z , High Z analog , Pull up , Pull Down .

               

            I am using CY8C28445-24PVXI 

            • 3. Re: Current Delivered by GPIO pin at 3.3 v
              user_14586677

              The max port current is the limitation for all pins total

                 

              current allowed in the port.

                 

               

                 

              You use the term source current, so that would be current sourced from Vdd

                 

              thru the P channel output transistor in the port driver.

                 

               

                 

               

                 

               

                 

               

                 

               

                 

               

                 

               

                 

              Regards, Dana.

              • 4. Re: Current Delivered by GPIO pin at 3.3 v
                stub.for.509020970

                 HI Dana thanks 

                   

                one silly question -

                   

                total current of port pin is 80mA and port are divided into two parts even and odd pins .

                   

                that means (80/2 ) 40mA for both even and odd ..

                   

                if we are using all 8 pins of port ...that means each pin deliver 10mA current .

                   

                Suppose if i want to use only two pins of port. and my requirement is 30mA current for each pin .

                   

                can i connect one pin to even port pins and other pin to odd port pins ?

                   

                or

                   

                both pin connect to even or odd pins port . it will automaticlly adjust the current ?

                   

                 

                   

                plzz inlighten me on this confusion ...........

                • 5. Re: Current Delivered by GPIO pin at 3.3 v
                  user_1377889

                  I am afraid you take the test-conditions as absolute ratings. Only the second row of dana's last post shows what you want to know: IOH = min 10mA under the given conditions.

                     

                   

                     

                  Bob

                  • 6. Re: Current Delivered by GPIO pin at 3.3 v
                    user_14586677

                    No, there is no active current management, its related to internal

                       

                    buss drop to insure logic noise margin specs.

                       

                     

                       

                    What are you actually driving ?

                       

                     

                       

                    Regards, Dana.

                    • 7. Re: Current Delivered by GPIO pin at 3.3 v
                      user_491123998

                       i want to connect two LED in parallel...

                         

                      Today i tested Red , blue and green LED with 3v coin cell battery .

                         

                      Red LED is taking = 20.1mA

                         

                      Blue is taking =1.64mA

                         

                      Green is taking = 2.55mA 

                         

                      if i connect two Red LED in parallel .it need 40mA total current . 

                         

                      if port not able to deliver such amount of current then voltage across the led will drop. then brightness of led will decrease.

                      • 8. Re: Current Delivered by GPIO pin at 3.3 v
                        user_1377889

                        Probably the first to give up is your coin-cell. The cr2032 has a capacity of ~200mAh which would result in 5hrs of your 2 red LEDs.

                           

                        The first LED that will shut down is the blue one, because forward voltage for blue LEDs is ~2.9V

                           

                        Forward voltages

                           

                        Red   1.6V

                           

                        Green 2.1V

                           

                        Blue 2.9V

                           

                         

                           

                        Working resistor is (UBatt - ULED) / ILED

                           

                        Red: (3.3 - 1.6) / 20mA = 85 Ohm. Regarding cell capacity I would suggest to reduce current to 5mA (using a low-current LED) and an R of 330 Ohms.

                           

                         

                           

                        Calculate for blue LED for yourself...

                           

                         

                           

                        Bob

                        • 9. Re: Current Delivered by GPIO pin at 3.3 v
                          user_14586677

                          I assume you dont actually mean two LEDs pin to pin parallel

                             

                          as they will not current share properly due to Vth differences.

                             

                           

                             

                          You can drive LEDs to ground or to Vdd, the former preferred because

                             

                          the Nchannel has better switch characteristics =

                             

                           

                             

                           

                             

                           

                             

                          The equation for Rled = ( Voh - Vled ) / Iled where Voh is estimated

                             

                          Vbatt - Vdspchannel, latter from spec in DC characteristics. This for driving

                             

                          to Vdd.

                             

                           

                             

                          For driving to ground Rled = ( Vdd or Vbatt - Vthled - Vol ) / Iled.

                             

                           

                             

                          The port can handle the current, you could parallel two pins to improve

                             

                          Vol.

                             

                           

                             

                          Regards, Dana.

                          • 10. Re: Current Delivered by GPIO pin at 3.3 v
                            user_491123998

                             what do you thing if i use switch mode pump and run M8C at 5V ... 

                            • 11. Re: Current Delivered by GPIO pin at 3.3 v
                              user_14586677

                              The SMP is not capable of supplying the LED current you

                                 

                              need, so you would drive LEDs to ground, and use an alternate

                                 

                              supply/regulator to supply LED current. In addition you have to

                                 

                              insure the pin voltage when led off does not violate the allowable

                                 

                              voltage relative to Vdd on PSOC.

                                 

                               

                                 

                              Regards, Dana.