thanks for your reply

i really don't understand the terrible choice of pin assignments here

i checked the data sheet and i see 10uA Vref current max, at 2.5Vref that would be about 8 LSBs at 2K

so i don't think that is acceptable

and then there is a whopping 1mA during acq which i guess is off the table ?

my thought at the moment (since i must have ISP and do not want to jump/unjump the ref during flash and crash development) is that i will use Vref = VDD and put a trimmer (yuck) on the VDD reg to get the tweaks right

i ran into this same sort of conflict on the same pin a while back while using the ULPW cap on that same pin