On Tue, Jan 6, 2015 at 5:41 PM, Slichter, Daniel H. <daniel.slich...@nist.gov> wrote: >> What connector do you want to use to get these fast-edge signals from the >> backplane to the dds cards and back? > > This is part of why I have been proposing LVCMOS signals instead of trying > for crazy bandwidths with differential signaling -
I don't see how LVCMOS helps with signal integrity over pin headers given that the bandwidth depends on the requirement on the rise time of the signal (and not really on the signalling standard). > the current design calls for the use of 2mm pin headers, back compatible with > the existing DDS boards, which are not going to give us the best performance. > By opting for surface mount instead of through-hole, we reduce the pin > capacitance somewhat, but it's still not ideal. > > If we are OK with losing the back-compatibility with previous designs, we can > think about using high-speed connectors e.g. SAMTEC QRM8, which are designed > for this sort of thing. The price and footprint of these connectors is > similar to the current 2 mm pin headers, but we would lose the > interoperability of old-style DDS cards. This is something we might discuss > at group meeting. In general, we are probably better off going to real > high-speed connectors, but it should be debated. If plain pin headers can not do the required < 300 ps edges (for the AD9915 SYNC_IN/OUT scheme or for reliable SYNC_CLK detection) the question has a simple answer. And if new bus connectors are required, this is the time to choose a COTS rack/bus system and not invent another. -- Robert Jordens. _______________________________________________ ARTIQ mailing list https://ssl.serverraum.org/lists/listinfo/artiq
