I'm attempting to replace my DRV8825's with TMC2130's on a Prusa i3 rework clone, 12 V RAMPS 1.4, motor currents have been accounted for. Since they don't work as well with 12 V than with higher voltages, I bought a 10-50 V, 10 A DC-DC converter to power the drivers (and steppers). On the RAMPS this is done simply by taking the VM pin out and soldering it on the other side to draw power from an external source.
It is stated everywhere that VM should be powered BEFORE VIO. Would it be valid to switch on a relay with the DC-DC converter and connect the VIO pin to RAMPS 5 V through it? Is it enough having both sources turn on at roughly the same time? I haven't found any indication on how much time there should be in between (or if there needs to be any).
Please tell me your own experience if you have attempted something similar, or any alternatives (aside from buying a new board, because I'll eventually build a CoreXY or something else) that may be valid.