LMH1219: Output AC coupling capacitor

Kitaura Shigeki

Part Number: LMH1219

Hi team,

My design connect output of the LMH1219 to GTH TRX of Xilinx Zynq Ultra Scale+.

The AC coupling for this differential signal is listed as 4.7uF in the LM1219 datasheet and 0.1uF in the Zynq.

Which one should be chosen ?

Regards,

S.Kitaura

0 Nicholaus_Malone over 1 year ago

Hi S.Kitaura,

0.1uF is too low. It should be 4.7uF. Where is the recommendation from Xilinx?

Thanks,

Nicholaus

0 Kitaura Shigeki over 1 year ago in reply to Nicholaus_Malone

Hi Nicholaus,

Thank you very much.

Xilinx recommendation are listed in "DC and AC Switching Characteristics (DS925)".

Thanks,

S.Kitaura

+1 Nicholaus_Malone over 1 year ago

Hi S.Kitaura,

I checked the Xilinx documentation just to be sure.

By the Cext specification of 100nF, it has a note (3):

3) "Other values can be used as appropriate to conform to specific protocols and standards."

So, please use the external coupling caps recommended by the SDI standard, which is 4.7uF.

Regards,

Nicholaus

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