5 Replies Latest reply on Dec 31, 2014 9:34 AM by mweal

    Edison V_VBAT_BKUP

    mweal

      I'm looking for some more information on the V_VBAT_BKUP features of the Edison.

       

      1) I want to power the RTC when the Edison is powered down (via PWRBTN# or equivalent).  The Edison may be powered down for a few months.  Does the Edison power the RTC (from VSYS, assuming it has battery power) while powered down like this?

      2) If not, can I power the V_VBAT_BKUP from the VSYS Battery and thus avoiding the need for a supercap?

        • 1. Re: Edison V_VBAT_BKUP
          Andre.M

          you need to power V_VBAT_BKUP to have a working RTC if Edison is switched off

          not sure if V_VBAT_BKUP is happy with 3.3 to 4.5V, some users provide 2.5V

          the Module Hardware Guide should be extended to provide the required V_VBAT_BKUP voltage range

          • 2. Re: Edison V_VBAT_BKUP
            CMata_Intel

            Hi mweal

             

            I think you could consider the suggestions in Section 5 from the Compute Module Hardware Guide. Also, in section 4.13 you could see the available information about V_VBAT_BKUP. You could search for more information about the PMIC in the Edison too. (SNB9024 Section 3.5)

             

            Regards;

            CMata

            • 3. Re: Edison V_VBAT_BKUP
              mweal

              CMata_Intel, thanks for the feedback.  The Compute Module Hardware Guide is not much help. Section 4.13 basically says you can hook up a 2.5V supercap  or battery and section 5 does not mention anything about the RTC backup.  I have searched (and searched and searched) for the SNB9024 and have been unable to find any more information for the device.

              • 4. Re: Edison V_VBAT_BKUP
                CMata_Intel

                Hi mweal

                 

                In the section 5.3 of the document you can see how the PMIC is powered inside the Edison Compute Module, and how the VSYS and VBAT are related. In the table 5, the VBAT pin is the input for the backup battery and VSYS is the system input power. The PMIC allows to use a rechargeable coin cell battery or a super-capacitor. You said that it could be powered down for a few months so you will need a coin cell battery that may work for that long, and always taking care of the voltage and current specifications for the PMIC as the document states in section 4.3.

                About the PMIC datasheet, I haven't been able to find it either, I think you could contact their support team and ask for the datasheet.

                 

                Regards;

                CMata

                • 5. Re: Edison V_VBAT_BKUP
                  mweal

                  CMata_Intel,

                   

                  I looked at section 5.3, and table 5.  One refers to VBAT and the other to V_VBAT_BKUP.  It is not clear if  VBAT in section 5.3 is short for V_VBAT_BKUP (RTC backup) or for full battery operation of the Edison.  I believe it is for full battery operation due to the reference is section 5.1 "Application of power to VSYS is interpreted as a battery insertion and will cause Edison to boot."

                   

                  I have made a request to TI for the data sheet, and have not received any reply as of yet.