Kinetis MicrocontrollersのトピックK28 Vrefh pin connection option https://community.nxp.com/t5/Kinetis-Microcontrollers/K28-Vrefh-pin-connection-option/m-p/752425#M45835 <HTML><HEAD></HEAD><BODY><P>I have a design that is power sensitive put I also need accurate adc readings. For this reason I'm adding a external prec ref voltage source. I will not be doing measurements all the time and If I shut down the prec ref I can save about 100ua. The only issue is that the Vrefh pin into the micro will be floating. Will this be a issue? The data sheet says unused pins short go to VDD but what happens if I let it float? Since I will not be doing any reading I would think it should not be a issue. It will have a impedance to gnd through the prec ref chip. Would that be good or bad?</P></BODY></HTML> Fri, 16 Feb 2018 21:32:12 GMT jasonlarson 2018-02-16T21:32:12Z K28 Vrefh pin connection option https://community.nxp.com/t5/Kinetis-Microcontrollers/K28-Vrefh-pin-connection-option/m-p/752425#M45835 <HTML><HEAD></HEAD><BODY><P>I have a design that is power sensitive put I also need accurate adc readings. For this reason I'm adding a external prec ref voltage source. I will not be doing measurements all the time and If I shut down the prec ref I can save about 100ua. The only issue is that the Vrefh pin into the micro will be floating. Will this be a issue? The data sheet says unused pins short go to VDD but what happens if I let it float? Since I will not be doing any reading I would think it should not be a issue. It will have a impedance to gnd through the prec ref chip. Would that be good or bad?</P></BODY></HTML> Fri, 16 Feb 2018 21:32:12 GMT https://community.nxp.com/t5/Kinetis-Microcontrollers/K28-Vrefh-pin-connection-option/m-p/752425#M45835 jasonlarson 2018-02-16T21:32:12Z Re: K28 Vrefh pin connection option https://community.nxp.com/t5/Kinetis-Microcontrollers/K28-Vrefh-pin-connection-option/m-p/752426#M45836 <HTML><HEAD></HEAD><BODY><P>Hi Jason,</P><P>I think it is ok if it float to ground. Please see&nbsp; this link:</P><P><A _jive_internal="true" href="https://community.nxp.com/message/419427?commentID=419427#comment-419427">https://community.nxp.com/message/419427?commentID=419427#comment-419427</A></P><P></P><P>Regards,</P><P>Jing</P></BODY></HTML> Thu, 22 Feb 2018 06:34:47 GMT https://community.nxp.com/t5/Kinetis-Microcontrollers/K28-Vrefh-pin-connection-option/m-p/752426#M45836 jingpan 2018-02-22T06:34:47Z