SLUC263 compensation calculator tool for TPS40055 reveals a relationship between the loop gain and Rkff value. The spreadsheet Control to Output Bode plot (the modulator gain, isn't it?) is much affected by Rkff while changing the input voltage has no impact at all on the loop gain.
Meanwhile, the loop compensation design procedure in the datasheet totally evacuates the relationship between the loop gain and Rkff; the modulator gain is based solely on Vin and a 2V ramp.
The design procedure explains how to select Rkff to obtain the desired UVLO threshold only. It does not explain how it impacts on the loop gain.
My problem is that I follow the design procedure and end up with something that can, according to the spreadsheet, become unstable depending on the Rkff value I use.
I feel the datasheet and the spreadsheet are in contradiction.
Can someone help me out with that?
Regards
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