Tool/software: WEBENCH® Design Tools
I remember why I have always hated Webench, back to the days when it was a Nat Semi tool. I created a Boost converter design a few days ago using the TPS55340, and had a resulting design generated. I came back to the design and tried to adjust some of the design parameters slightly and now get the result that this part cannot not be used because it would not result in a stable design. I then went back to the original parameters and got the same message. I then tried entering designs directly from examples from the data sheet and this part was never listed as a valid part to use. Sometimes it was the same lack of phase margin and sometimes it was that the temperature rise was too great. I then clicked on the link in the data sheet in section 8.2.1.2.1 that says "Click here" to create a custom design using the TPS55340 device with the WEBENCH® Power Designer. With the default parameters that came up of 5 to 8 V in, 12V at 1A out and 30 C, I hit "Open Design". I got the message that "Design cannot be created with this device". I then hit the button for Show Why Parts Were Not Found and got the same message as my original design which is "This design is not stable due phase margin either smaller than 35 or greater than 120. If I try the design from Table 1 in the data sheet just above the link, 5 to 12 V in, 24 V out at 800mA, The TPS55340 is not listed as a valid device. When I search on why this part is not found it has the same Phase margin message in the Comment field. I have not been able to find any design that Webench says this part works for even though I have a full design report from when it generated a valid design for me about a week ago! There I had 4 to 5 V in, 32V at 0.5A out. Was the original simulation wrong and I should not use this part or has someone messed up the program? Could I have changed some defaults that the program uses when I load Webench that causes it to give me these problems?
