I found that when using the What If analysis tool on the TPS54418 to look at adjusting the copensation, performing a calculation on the Poles and Zeros option would throw the total gain result way out of whack. The results would show crossover freq at 0 Hz and gain Margin of -1 deg no matter what values are entered or even if no new values are entered.
To reporduce problem - Select TPS54418 EVM on Switcher Pro. Open What If analysis. Select Compensation tab. Select Poles and Zeros Frequencies option. Hit Calculate button. Observe unusual results. One does not have to enter any changes to the original Poles and Zeroes values to trigger poor result. I also found this happened with TPS54218, TPS54318 models. This problem shows up in both Desktop and On-Line version of Switcher Pro.
When the issue happens, the compensation R's and C's values change to some extreme values. If I manually return the R's and C's to their original values using the "Components" mode, then the loop results return to the original response. But entering anything on Poles and Zeroes mode causes the erroneous results.
We understand that there is an issue on 'What If Analysis' page, when user clicks on 'calculate' button without changing any values, Fc, gain and phase margin and compensation component values change. We are working on fixing this.
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