Yes, and I was thinking of doing that (for buck and boost), especially since as I build more drivers I see that the FET I’m using gives me consistently close to 2mΩ, and that it doesn’t go up much with heat (but I still need to do more measurements of that).
So I mentionned the lower limit of 6mΩ for the total resistance, but we could maybe go down to 5 (or 5.5 as mentionned due to the stray resistance).
And the lower limit for Vsense would be 40~50V so that it’s reliable (no flicker) so considering that for 5A we could do 5.5mΩ, 27.5mV Vsense, limits the minimum to 2/1023 of each range so that the min Vsense is 54uV, and we get 250 000:1 dimming range, still largerly sufficient.
That said for a linear driver the efficiency gain is only in dropout (which is very efficient) so this has a limited effect.