Is it possible for LT8471 to handle 42V input and generate +/-20V bipolar output, 0.3-0.4A per rail? I was looking at figure 10A which is pretty much what I need, but the voltages are a bit off.
If it's possible, what should I change besides the feedback resistors? If not, are there other chips that are suitable for this task?
No this will not work. The max ABS of the VC2 to VE2 is 60V, the voltage stress is VIN+|Vout|, this is 62V for -20V rail in your case. You can look, though, at link below as possible solution. Also I'll forward your message to our marketing department, they might advise in this matter. https://www.analog.com/en/analog-dialogue/articles/overcoming-constraints-design-precision-bipolar-power-supply-on-a-simple-buck-controller.html
Victor, thanks for the answer. This is what I thought initially.
It would be very convenient to have a single chip solution for my task. Otherwise I'll have to make two separate converter sections for each rail.