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DS90UB936-Q1: S90UB936 AC-coupling capcitor selection at sync clock mode and STP connection

Cheney Hu
Prodigy 620 points
Part Number: DS90UB936-Q1

​Hi Team,

There is a question about the AC-coupling capacitor's selection of DS90UB936 want to consult to you that:

Customer's application is '1xDS90UB935 + 1xDS90UB936' with synchronous mode at 25MHz REFCLK(XTAL), so refer to datasheet page-28, the line rate=4.0 Gbps & back channel frequency =50MHz right?

If based on line rate & fBC above, and table 228 on 936 datasheet below, In addition, 8.2.2 Detailed Design Procedure has the following description."For 2G operation or back channel frequency of ≤ 10 Mbps, the higher value AC-coupling capacitors 100 nF /47 nF are recommended."(Coaxial)

In other words, does it mean that a small capacitor of 33 nF is recommended for fast communication at 4 Gbps?

 Anyway the overall question is:

For DS90UB936, with STP connection, synchonus mode, 4.0Gbps line rate & 50MHz back channel frequency, whether it recommend to use 33nF AC-coupling capacitor?

Thanks & BRs,

Cheney