LPC MicrocontrollersのトピックLPCXpresso OM13058 LPC11U68 VREFN maximum voltage? https://community.nxp.com/t5/LPC-Microcontrollers/LPCXpresso-OM13058-LPC11U68-VREFN-maximum-voltage/m-p/604166#M23522 <HTML><HEAD></HEAD><BODY><P>Is there a specification for maximum VREFN voltage? In the datasheet and user manual there are recommendations for best performance, but no hard limits except for the upper limit on VREFP.</P><P></P><P>From the user manual, page 304 :</P><P>"Remark: For best performance, select VREFP and VREFN at the same voltage levels as VDDA and VSSA. When selecting VREFP and VREFN different from VDDA and VSSA , ensure that the voltage midpoints are the same:<BR />(VREFP-VREFN)/2 + VREFN = VDDA/2"</P><P>I am attempting to set VREFN at approximately 2.7V and VREFP at approximately 3.2V, for about 0.5V difference, using LM385 voltage references. VREFP pin is fine, I can connect either reference to it, but with VREFN pin it is pulled down to 0.85V. I can't see anything on the OM13058 schematic to explain this so I am wondering if it some kind of internal protection in the MCU itself?</P><P></P><P>Does anyone have any experience trying to use a similar high VREFN voltage?</P></BODY></HTML> Fri, 09 Sep 2016 05:09:06 GMT dirtyd 2016-09-09T05:09:06Z LPCXpresso OM13058 LPC11U68 VREFN maximum voltage? https://community.nxp.com/t5/LPC-Microcontrollers/LPCXpresso-OM13058-LPC11U68-VREFN-maximum-voltage/m-p/604166#M23522 <HTML><HEAD></HEAD><BODY><P>Is there a specification for maximum VREFN voltage? In the datasheet and user manual there are recommendations for best performance, but no hard limits except for the upper limit on VREFP.</P><P></P><P>From the user manual, page 304 :</P><P>"Remark: For best performance, select VREFP and VREFN at the same voltage levels as VDDA and VSSA. When selecting VREFP and VREFN different from VDDA and VSSA , ensure that the voltage midpoints are the same:<BR />(VREFP-VREFN)/2 + VREFN = VDDA/2"</P><P>I am attempting to set VREFN at approximately 2.7V and VREFP at approximately 3.2V, for about 0.5V difference, using LM385 voltage references. VREFP pin is fine, I can connect either reference to it, but with VREFN pin it is pulled down to 0.85V. I can't see anything on the OM13058 schematic to explain this so I am wondering if it some kind of internal protection in the MCU itself?</P><P></P><P>Does anyone have any experience trying to use a similar high VREFN voltage?</P></BODY></HTML> Fri, 09 Sep 2016 05:09:06 GMT https://community.nxp.com/t5/LPC-Microcontrollers/LPCXpresso-OM13058-LPC11U68-VREFN-maximum-voltage/m-p/604166#M23522 dirtyd 2016-09-09T05:09:06Z Re: LPCXpresso OM13058 LPC11U68 VREFN maximum voltage? https://community.nxp.com/t5/LPC-Microcontrollers/LPCXpresso-OM13058-LPC11U68-VREFN-maximum-voltage/m-p/604167#M23523 <HTML><HEAD></HEAD><BODY><P>Hi,</P><P>The set of the VREFP and VREFN should follow the rules:</P><P>1. The VREFP voltage level must be between 2.4 V and Vdda.</P><P>2. (VREFP-VREFN)/2 + VREFN = VDDA/2</P><P>Hole it helps.<BR />Have a great day,<BR />Ping</P><P></P><P>-----------------------------------------------------------------------------------------------------------------------<BR />Note: If this post answers your question, please click the Correct Answer button. Thank you!<BR />-----------------------------------------------------------------------------------------------------------------------</P></BODY></HTML> Tue, 13 Sep 2016 06:05:16 GMT https://community.nxp.com/t5/LPC-Microcontrollers/LPCXpresso-OM13058-LPC11U68-VREFN-maximum-voltage/m-p/604167#M23523 jeremyzhou 2016-09-13T06:05:16Z