Question 1
The EVM seems to be targeted for using twisted pair connection to the deserializer. But we want to use coax, so I think we need to make some BOM changes. Reviewing the SCH in the EVM documentation (SNLU169 - December 2014), I noticed that some of the component reference designators don't match our EVM (marked SV600978-003 Rev B). For example, the SCH shows that R112 and R118 are shunt resistor options at J11 and J13. But on our EVM the shunt options at those connectors are silkscreened as R109 and R114. Where do I find a SCH that matches the reference designators on our EVM?
Question 2
We're using the DS90UB948 deserializer and want to use coax (i.e. single-ended) connection. The '948 and '949 datasheets (and EVM documents) gave slightly different details on how to do this. But in the positive signal path we tried AC-coupling cap values of 100nF, 47nF, and 33nF. Also, in the negative signal path, we tried AC-coupling cap values of 33nF and 15nF. None of them worked. We finally switched to "differential coax" (one coax for the positive signal path, a separate coax for the negative signal path) with 100nF AC-coupling caps, and that seems to work. But that requires twice as many coax connections. What are we missing? I did change the Mode1 setting to Coax, but once we were using "differential coax", it didn't seem to matter if the Mode1 setting is Coax or Twisted Pair.
