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TPS51200: Frequently Asked Questions and Answers

Part Number: TPS51200

Hello all, 

I've seen the following on the FAQ: "At least one 10uF capacitor needs to be placed close to TPS51200 VO pin. Other VTT capacitors can be placed at either TPS51200 side or DIMM side."

So could someone please check my layout to make sure that I've done it correctly?

Schematics:

And the layout:

As you can see on the schematics, my VO capacitors are C80, C81 and C82. On the layout, C82 is right next to TPS51200 pin 3 and C80 & C81 are near the load. Is this OK?

Thank you in advance!

Alex

  • HI Alex,

    The position of VO capacitors looks fine. Below are my other comments.
    1. It is suggested to add one more 10uF for VLDOIN pin.
    2. For better VO regulation at load side, it is suggest to connect VOSNS pin to load side.

    Thanks
    Qian
  • Hello Qian,

    Thank you for your quick reply.

    Regarding your comments:

    1) Thank you. I'm going to add one more 10uF.

    2) How would I connect it? A long trace to, let's say, C80? (Please see the following picture). What could happen if I leave it as it is on my original post? Also, what are the implications of having this long trace?

    Regards,

    Alex

  • Hi Alex,

    If VOSNS is connected to the load side, the long trace should be away from noise source. If it is multi layer board, place the trace in inner layer with low noise signal. You can also add a 100pF bypass cap between VOSNS and ground to filter potential noise, place this cap close to VOSNS pin.

    Connecting VOSNS to local cap (C82) is fine when curernt is small and the PCB impedance between regulator and load is low. But still, the voltage regulation on load side will not be as good as the regulatoin with VOSNS connected to load side.


    Thanks
    Qian
  • Thank you very much Qian!