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WEBENCH® Tools/LM3478: Webench tool flexibility

user4893275
Prodigy 20 points
Part Number: LM3478

Tool/software: WEBENCH® Design Tools

I am using Webench power designer and I am finding it extremely frustrating that I can not go into a schematic design and change the load resistance value. Well I can, but there are arbitrary limits set by the tool which it does not seem possible to change. I am investigating an issue with a DC-DC converter where I know I have problems and I want to explore the limits. In particular I want to look at the Bode plots and determine how close I am to stability in the design. 

The design is a DC-DC converter generating 48 V from 12 V with an output current range from 5 mA to 125 mA. I have a design which sources 5 mA and I want to now increase the current to 15 mA. I cannot edit the Rload value on the existing design and if I try to create a new design and change the component values to those I have in the 5 mA design, when I come to edit the compensation capacitors the tool is not allowing me to set the values I want. I suspect that this is because the value will make the design unstable and the tool is trying to be helpful and not allowing me to do it.

The tool is powerful but does not have enough flexibility to enable me to explore the design space.

  • 0
    TI__Guru* 78320 points

    For this case, you should set your load to max (125mA), and the Webench will generate a design to handle the power up to that max load. If you just input 5mA, the Webench interprets it as your max power and a different set of components will be selected suitable for that power level. Then, you cannot decrease the load resistor for higher power because the design only supports 5mA. Always put your max load as the input condition for Webench.