Oscillator selection
Issues related to IVT3025/CFPT9301 oscillators, mounted by default on SPEC boards:
- cannot be used for White Rabbit DMTD clock because of too low tuning range. We need 100 ppm.
- can cause soldering issues (IVT3025 consists of two ceramic plates soldered together already)
- CFPT9301 oscillator is very expensive. Could be replaced with a much
cheaper VM53S3 oscillator (20, 25 or 40 MHz) with a 3 V LDO regulator
(for example LP5951MF-3.0).
- both oscillators don't have to be of exactly 25 MHz. The 25 MHz
version seems to be difficult to get, but it could be replaced with more
popular 20 or 40 MHz. CDCM61004 PLL configuration resistors would need
to be changed to produce 125 MHz REFCLK from the new input frequency.