5 Replies Latest reply on Oct 31, 2017 12:58 PM by Carlos_A

    XL710 Power Supply (hardware)

    Matic Community Member

      I'm designing power supply for XL710 with LTC3833. My reference is XL710 Reference Schematics. Could you please explain which ground connection should be used on capacitor C85 (On-Die sensing control capacitor). Is this PGND or SGND?

       

      Intel® Ethernet Controller XL710 Reference Schematic

       

      Best Regards Matic

        • Re: XL710 Power Supply (hardware)
          Carlos_A Brown Belt

          Hello, Matic:

           

          Thank you for contacting Intel Embedded Community.

           

          The PGND (pin 12 of the LTC3833) and SGND (pin 21 of the LTC3833) pins are connected together (both pins are connected to GND). You can confirm this information on sheet 17 (page 18) of the cited Reference Schematic.

           

          Due to this fact,  the C85 can be connected to any of the cited pins as you may notice in the yellow highlighted areas of the following schematic portion from the listed document:

           

           

          We hope that this information is useful to you.

           

          Best regards,

          Carlos_A.

            • Re: XL710 Power Supply (hardware)
              Matic Community Member

              Hi Carlos!

               

              Thank you for quick reply. If I check LTC3833 datasheet there are two gorunds (PGND and SGND). SGND is used for small signals. Both grounds are connected together in one point only using a single PCB trace. Could you please check your PCB?

               

              http://cds.linear.com/docs/en/datasheet/3833f.pdf

               

              Best Regards Matic

                • Re: XL710 Power Supply (hardware)
                  Carlos_A Brown Belt

                  Hello, Matic :

                   

                  Thanks for your reply.

                   

                  In order to be on the same page, could you please tell us if this consultation is related to a technical problem? In case that your answer is affirmative, please let us know all the details related to it.

                   

                  By the way, could you please clarify us what you mean with PCB? Is it related to schematics or layout documentation; or a physical board implemented by Intel? Please give us know a detailed description.

                   

                  Finally, as a reference reviewing the website of the manufacturer of the device listed on your last communication, we found the same implementation that is stated the schematics mentioned on our first communication as you notice at:

                   

                  http://www.linear.com/product/LTC3833

                   

                  Please give us the information that should answer the previous questions.

                   

                  Best regards,

                  Carlos_A.

                    • Re: XL710 Power Supply (hardware)
                      Matic Community Member

                      Hi Carlos!

                       

                      No this thread is not related to a technical problem but I need to design layout correctly that problem will not escalate in future!

                      Intel design: Intel XL710 design has only one ground (schematics) but I guess that XL710 reference layout  has separate ground planes (PGND and SGND or some other Intel layout marking) at LTC3833 dcdc controller.

                      Linear tech. design: LT3833 (datasheet and demo board) strictly demand 2 separate ground planes (SGND, PGND) which are connected in single PCB trace.

                       

                      My question is: Which ground is used on C85?

                      If you could not find an answer could you please share your layout with me that I can check the Intel LTC3833 controller layout?

                       

                       

                      LTC3833 datasheet: Ground planes demand

                      SGND (Exposed Pad Pin 21/Exposed Pad Pin 21): Signal Ground Connection. The SGND exposed pad must be soldered to the circuit board for electrical contact and rated thermal performance. All small-signal components should be connected to the signal ground. Connect signal ground to power ground only at one point using a single PCB trace.)

                       

                      http://cds.linear.com/docs/en/datasheet/3833f.pdf