ertm15: Axtal OCXO reference output
Axtal reference voltage output should be 5.0V, but it is 5.112V. Higher than the DAC power supply. Next actions:
- contact Axtal to check
- mount REF5045 on the rev. 1 to check if that was the cause of jumps
- rev 2 board: mount a reference voltage, candidates are REF5050 (5.000V) or REF5045 (4.500V), depending if we want to use 11.2V or 5V to power it.