@KimSuB wrote:
I'm trying to use the (sic) 64pin STM32F722 part
There are two:

@KimSuB wrote:
I can't find the document
Where did you look?
The STM32F722RE Product Page suggests the NUCLEO-F722ZE:

You can get the schematics for that from its Product Page - on the 'CAD Resources' tab:
https://www.st.com/en/evaluation-tools/nucleo-f722ze.html#cad-resources
@KimSuB wrote:
I could find the reference schematic for the BGA part of 100 pins but I need one for 64 pins.
The NUCLEO-F722ZE has an LQFP144 part.
The number of pins is really immaterial for a reference schematic - just ignore the extras!
And, as @mƎALLEm already said, see AN4661.
A complex system that works is invariably found to have evolved from a simple system that worked.A complex system designed from scratch never works and cannot be patched up to make it work.