topic GoldCap on Battery Pin to power just the RTC? in i.MX Processors https://community.nxp.com/t5/i-MX-Processors/GoldCap-on-Battery-Pin-to-power-just-the-RTC/m-p/161169#M3395 <HTML><HEAD></HEAD><BODY><P>Reading Chapter 11 (Power Supply) I don't really get a feeling whether it should be possible to use a GoldCap (say 1 Farad) at the Battery pin - just to power the RTC for a few hours when VDD5V is not available.</P><P>&nbsp;</P><P>It should be possible when using the linear regulators or the DC/DC using the VDD4P2 path.</P><P>&nbsp;</P><P>The GoldCap itself has roughly 100 Ohms of internal resistance, so any switchover event resulting in a larger current from the Battery pin might bring the voltage low enough to trigger a problem.</P><P>&nbsp;</P><P>Is it possible that such a brief current surge can happen on the Battery pin, for example when VDD5V is suddenly lost?</P><P>&nbsp;</P><P>Considering the rather large current on the Battery pin during off state (13.5 typ/30 max) uA, a GoldCap solution might not be the best anyway, but in our typical applications a loss of VDD5V is not the operational case; or if, it is usually brief; or if enduring, a loss of time is acceptable.</P><P>&nbsp;</P><P>Best Regards,</P><P>Reinhard</P></BODY></HTML> Tue, 05 Jul 2011 07:42:53 GMT ReinhardMeyer 2011-07-05T07:42:53Z GoldCap on Battery Pin to power just the RTC? https://community.nxp.com/t5/i-MX-Processors/GoldCap-on-Battery-Pin-to-power-just-the-RTC/m-p/161169#M3395 <HTML><HEAD></HEAD><BODY><P>Reading Chapter 11 (Power Supply) I don't really get a feeling whether it should be possible to use a GoldCap (say 1 Farad) at the Battery pin - just to power the RTC for a few hours when VDD5V is not available.</P><P>&nbsp;</P><P>It should be possible when using the linear regulators or the DC/DC using the VDD4P2 path.</P><P>&nbsp;</P><P>The GoldCap itself has roughly 100 Ohms of internal resistance, so any switchover event resulting in a larger current from the Battery pin might bring the voltage low enough to trigger a problem.</P><P>&nbsp;</P><P>Is it possible that such a brief current surge can happen on the Battery pin, for example when VDD5V is suddenly lost?</P><P>&nbsp;</P><P>Considering the rather large current on the Battery pin during off state (13.5 typ/30 max) uA, a GoldCap solution might not be the best anyway, but in our typical applications a loss of VDD5V is not the operational case; or if, it is usually brief; or if enduring, a loss of time is acceptable.</P><P>&nbsp;</P><P>Best Regards,</P><P>Reinhard</P></BODY></HTML> Tue, 05 Jul 2011 07:42:53 GMT https://community.nxp.com/t5/i-MX-Processors/GoldCap-on-Battery-Pin-to-power-just-the-RTC/m-p/161169#M3395 ReinhardMeyer 2011-07-05T07:42:53Z