• State
  • Locked Locked
  • Replies 3 replies
  • Subscribers 62 subscribers
  • Views 206 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.

TPS61376: Compensation filter calculations

Michael Weston
Prodigy 120 points
Part Number: TPS61376


Tool/software:

Hello,

There are bits of information missing to do this on my own.  What value should I be using for Fcomp1, Fcomp2 and Fcomz?

It looks like everything else has a definition but it would sure be nice if this part was modelled in Webench! It appears that this calculation is based on the output filter and I am using the same capacitance total on my board (not specifically the same parts) so I set the components in the compensation filter to the same as the EVM.  The problem is that the EVM doesn't work properly and neither does my design.  The output voltage falls greatly well before any current limits are reached and so I cannot get nearly enough power to the load unless it is such a small load that the current stays under 100mA.  I'm not sure what to do but I thought I might start with tweaking the compensation filter but I need more information.

Thanks,

Michael

  • 0
    TI__Genius 9655 points

    Hi Michael,

    Please share working condition when the unexpected Vout drop happens. Please share Vin, Vout and Iout.

    Best Regards,

    Travis

  • 0 in reply to Travis Wang
    Prodigy 120 points

    Hello Travis,

    I will detail the operating environment.

    Input capacitance - (10uF + 10uF + 1uF) ceramic + (680uF) Electrolytic (due to long power wires)

    Output capacitance - (10uF +10uF + 1uF) ceramic + (47uF) Electrolytic

    Vin: range is 3V to 7V, 6V nominal

    Vout; 9V

    Iout: 200mA max (input current limit set to 295mA)

    We found out yesterday that putting an ammeter in between the output and the test loads was causing the TPS61376 to scale back the output current and voltage.  Putting the meter into the 10A range helped to restore most of the output but it is a bit baffling.  Putting a jumper back in place of the ammeter would restore the output.  This is still why I am wondering if the compensation filter is important to improving the results but I need these unknown values (Fcomp1, Fcomp2, Fcomz) to be able to analyze it on my own!

    Thanks!

    Michael

  • 0 in reply to Michael Weston
    TI__Genius 9655 points

    Hi Michel,

    Change Rlim to 14.4kΩ, pull Isel pin high and try again. Please capture waveform of Vin , sw and Vout pin.

    Best Regards,

    Travis