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TPS650861: 5V Tolerance

Don Schelle
Expert 4150 points
Part Number: TPS650861

Hello,

I'm planning on using the TPS650861 from a 5V input rail (with VSYS generated at 5.8V).    What is the required tolerance on the incoming 5V rail?    Can I use +/-10%?    Also, how far apart can the 5V rail be from VSYS?    Suppose I wanted to make VSYS 6.0V with a 5V +/-10% main rail.   Would that be OK too?

Don

  • 0
    TI__Genius 12735 points

    Hi Don,

    While we strongly recommend keeping the VSYS voltage near the true input voltage to the FETs (in this case 5.8V and 5V respectively) this is for optimization of the rails and for best performance. VSYS at 6V should not be an issues as long as the supply to VSYS will not droop before 5.6V during the startup in-rush of the device. I would not recommend going beyond 6V as they may end up running in to issues with device performance as they continue to increase VSYS voltage over the main input voltage but 6V should be okay.

    Best regards,

    Layne J

  • 0 in reply to Layne J
    TI__Expert 4150 points

    Thanks Layne,

    Regarding the 5V input.   Is it OK if it droops to 5V - 10% (i.e. 4.5V)?

    Don

  • 0 in reply to Don Schelle
    TI__Genius 12735 points

    Hi Don,

    As long as the 5V supply does not go below 4.5V it will likely not be an issue. In section 6.3 you can see the power input to the external FETs must be 4.5V to 21V, so as long as the input stays in this range I do not expect any issues.

    Best regards,

    Layne J