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WEBENCH® Tools/LM2840: LM2840 inductor value

Part Number: LM2840
Other Parts Discussed in Thread: LM2841, LM2842

Tool/software: WEBENCH® Design Tools


I am creating power circuit with your part LM2840 with following parameters:

Vin: 6 to 30 V
Vout: 3,3 V
Iout: 100 mA
fsw: 550 kHz (X part)

I am trying to calculate inductor value and for max Vin (30 V) and 30 mA Iripple (as suggested in datasheet) I am getting 178 uH.
However in datasheet there is an example (Figure 9), which has only 15 uH inductor for even larger Vin range.
How is this possible? Where am I making mistake?

Webench fails to find solution using this part (due phase margin), but in datasheet you have working example (Figure 9).

This problem is also related with parts LM2840, LM2841, LM2842 - they differ only in Imax, but the equations are the same (according datasheet).

I also read these threads, but they didn't help:

Thank you for your answers.