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TPS546D24A: WEBENCH design error

Matt Reaves
Prodigy 100 points
Part Number: TPS546D24A

Hello,

I am trying to use WEBENCH to provide a converter design for my system. Everything goes fine, and I've chosen the suggested design based on the TPS546D24A. However, when I go to "Customize", I see an error notification that says:

"DESIGN ERROR MESSAGE: Compensation setting does not give the required VLOOP; try changing the VLOOP gain, GMV*Rvv, to match the recommended VLOOP in the OPERATING VALUES Compensation tab. "

However, I can't for the life of me find how to make this go away.

Here are my design parameters:
Input: DC 10 V - 14 V
Output: 3.6 V at 45 A
Temp: 85 °C
Vin Nominal: 12 V
Iout Nominal: 35 A

Can anyone provide assistance to determine whether or not the suggested design is viable?

On another note, it also says that "Simulation is not enabled for this design." Can anyone help enable the simulation so I can further verify the design?

  • 0
    TI__Guru 56985 points

    Matt,

    I am checking on the source of that error with our WeBench tools development team.  I tried entering the same values into WeBench myself, and I see the same error.  When I review the design, I believe the issue is that with the selected inductor (1.0uH) and Output Capacitors (3x 10uF + 1x 180uF) it can't find a pin programmable compensation solution.

    When I enter the design into the design spreadsheet, I run into an issue with the current loop and voltage loop gain ratios (target 2:1) across all of the pin-programmable compensation options.

    With a 1uH inductor, ILOOP of 7 gives a current loop bandwidth of about 55kHz.  The voltage loop bandwidth would need to be 27kHz or less, but the capacitors don't support, even for VLOOP gain of 0.5.

    If you let me know what transient performance you need on this 3.6V output (amplitude of transient current and allowable depth of Under/Overshoot) I can recommend a minimum VLOOP option to meet that requirement and the output capacitance needed to stabilize the output.

    If you could select a smaller inductor, 0.68uH or 0.5uH, the current loop bandwidth that could be achieved with pin-programming would be higher, allowing less output capacitance to be used to meet the same transient performance.

    Regarding the simulation, the 2-phase model is not set-up for the TPS546D24A, but you can simulate half of the design with 1/2 of the current.