• State Resolved
  • Locked Locked
  • Replies 3 replies
  • Subscribers 64 subscribers
  • Views 424 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

TPS54618 Datasheet Design Calculation Questions

trevdawg122
Prodigy 100 points
Other Parts Discussed in Thread: TPS54618

I have a few questions about the TPS54618 datasheet. The first question is concerning compensation network component selection on page 24. The datasheet recommends using SwitcherPro but the part is not available in the SwitcherPro library. Is there a substitute or plans to add this part?

Also on page  24, equations 40 and 41, it looks like I should use Ro and Co from figure 37, though equations 19 and 20 do not agree. I also don't see a value for Ro.

Thanks,
Trevor

  • 0
    TI__Guru**** 191445 points

    i'm noot sure about switcherpro support for this device.  When the device was released, we planned for it, but we may be going in a different direction w/ regard to support tools in the future.

     

    As far as the datasheet is concerned, there are a couple probelms.  Firs there is dfference in termonology between two parts of the document written by different authors.  In Fig. 37 RO and CO refer to the output cpacitiance and output resistance of teh transconductance amplifer.  In the design equations Co is the output capacitance while Ro is the output voltage divided by the output current (Vo/Io = Ro).  Also it looks like there is a translation error in equation 40.  It is not actually a "typo" as equations are graphic elements.  They are sometimes not converted properly when the online PDF file is generated.  Gm should be gmea and VIgm should be gmps.  If you can get past this, the equations are otherwise correct.  you should also know that this is a simplified approximation.  Datasheet changes are tedious, it may take a while to update it.

  • 0 in reply to JohnTucker
    Prodigy 100 points

    I found some additional problems. I do not see electrical specifications for the VREF accuracy, line regulation and load regulation. I do see a voltage accuracy figure on the first page of the datasheet which may account for the VREF accuracy, but there isn't one listed in the electrical specifications.

    Thanks,
    Trevor

  • 0 in reply to trevdawg122
    TI__Mastermind 35165 points

    Hi Trevor,

    On page 3 in the Electrical Characteristics table you can find it listing the 1% Vref accuracy over the Vin and temperature range.  Min = .791V, Typ = .799V, Max = .807V

    As for line and load regulation, Figures 47 and 48 show this with the circuit designed in the step-by-step design procedure.

    Hope this helps.

    Regards,
    Anthony