I have a serdes pair consisting of a DS92LV2411 serializer and a DS92LV2412 deserializer. The below pic demonstrates the suggested electrical connections from TI. My questions has to do with the ac coupled transmission lines. the Data sheet says that DOUT+/- (2411) and RIN+/- (2412) need to be coupled using a 0.1uF cap on each pin. My application is such that the transmission lines are such that the DOUT+/- pins of the 2411 go to traces (PCB1) to a header and into a new PCB (PCB2) and directly to the RIN+/- pins of the 2412. Please assume that all signals are properly AC coupled. Also assume that the total length of signal path (Dout to Rin) is <5in.
The other criterion of the design is that the coupling capacitors on the RIN pins of the 2412 be each composed of 2 caps in series.
So my question is: Can I use two 0.2uF caps in series to get the effective capacitance of 0.1uF required for the ac coupling of the transmission lines? Or will this set up lead to problems with the signals?
Ideally it is best to use the four caps and singles at each end as shown. The doubles in series, will have a bit more parasidic load and also effect the T-line properties more. Usually 0402 or 0603 caps are used and they also provide a nice test point. I would recommend the standard approach even though it is board and short.
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