topic Re: Measure current and voltage with K26 in Kinetis Microcontrollers https://community.nxp.com/t5/Kinetis-Microcontrollers/Measure-current-and-voltage-with-K26/m-p/745394#M45388 <HTML><HEAD></HEAD><BODY><P>Hi Javier,</P><P>I guess this is a very low frequency ADC test circuit. The load and the battery will not change in a high frequency. So I think it is nessesary to put a small cap near the AD pad. Because in ADC there is a Cadin. It's value is around 5~10pf. You can see it in datasheet. Since there is a big resistor R2 before ADC, Cadin will cause AD value distort. I think the value of the CAP should over 50pf. Details please find in AN4373. You can search this document on NXP website. <BR />As to VREF select, please refer to section 39.3.3(Voltage Reference Select) in reference manual. You can also use the examples in SDK.</P><P></P><P>Regards,</P><P>Jing</P></BODY></HTML> Tue, 23 Jan 2018 07:16:30 GMT jingpan 2018-01-23T07:16:30Z Measure current and voltage with K26 https://community.nxp.com/t5/Kinetis-Microcontrollers/Measure-current-and-voltage-with-K26/m-p/745393#M45387 <HTML><HEAD></HEAD><BODY><P>Hello!</P><P></P><P>I need to measure current and voltage with MK26FN2M0VMI18</P><P>I have a DC input from 5V up to 28V</P><P></P><P>Is it possible to measure it with a shunt resistor resistor of 0m50 and the ADC?</P><P></P><P>If so, I need to use VREF or VREF_OUT ?</P><P></P><P><A href="http://microcontrollerslab.com/wp-content/uploads/2015/05/Digital-Ammeter-using-pic-microcontroller.jpg">This circuit</A> can serve ?, it is similar to my requirements. If so, I have to place the R1 closed to GND and R2 closed to K26F ADC pin?</P><P></P><P>Best regards.</P></BODY></HTML> Mon, 22 Jan 2018 13:03:56 GMT https://community.nxp.com/t5/Kinetis-Microcontrollers/Measure-current-and-voltage-with-K26/m-p/745393#M45387 javierhernande1 2018-01-22T13:03:56Z Re: Measure current and voltage with K26 https://community.nxp.com/t5/Kinetis-Microcontrollers/Measure-current-and-voltage-with-K26/m-p/745394#M45388 <HTML><HEAD></HEAD><BODY><P>Hi Javier,</P><P>I guess this is a very low frequency ADC test circuit. The load and the battery will not change in a high frequency. So I think it is nessesary to put a small cap near the AD pad. Because in ADC there is a Cadin. It's value is around 5~10pf. You can see it in datasheet. Since there is a big resistor R2 before ADC, Cadin will cause AD value distort. I think the value of the CAP should over 50pf. Details please find in AN4373. You can search this document on NXP website. <BR />As to VREF select, please refer to section 39.3.3(Voltage Reference Select) in reference manual. You can also use the examples in SDK.</P><P></P><P>Regards,</P><P>Jing</P></BODY></HTML> Tue, 23 Jan 2018 07:16:30 GMT https://community.nxp.com/t5/Kinetis-Microcontrollers/Measure-current-and-voltage-with-K26/m-p/745394#M45388 jingpan 2018-01-23T07:16:30Z