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Registered: ‎07-17-2017

MGT Calibrated Termination Resistors - KIntex Ultrascale

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Hi,

 

I am interfacing to a DAC and the datasheet for the DAC recommends that the FPGA transmitter have a 100 ohm source resistor across the P and N pins (attachment included).

I noticed in the UG576, Ultrascale  GTH Transceiver Use Guide, it mentions that there are two calibrated termination resistors for the transmitter(attachment included).

Could these be used as recommended by the DAC datasheet? Are they controllable by the user? How do they get calibrated?

 

Thanks,

 

Jeff

 

calibrated_termination_resistors.png
SGMII_Interface.png
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roym
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Registered: ‎07-30-2007

There is always termination.  It is 100 ohms after configuration.  The rcal resistor is required to be 100 ohms or very close.  

We are interoperable with any compliant SGMII interface like this so there shouldn't be any trouble at all.  




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roym
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Registered: ‎07-30-2007

Yes,  I believe our GT could drive this DAC.  The calibration is done by the FPGA on configuration.  A current is driven through a known 100 ohm resistor, the RCAL resistor and measured.  Internally the resistance is calibrated to generate the same resistance.  It is not recommended to change the calibration resistance and I don't think you would need to.  If you send the part number I can look at their data sheet and try to confirm compatibility.




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Registered: ‎07-17-2017

Thanks for your reply. I have attached the datasheet. The part is a CPU and not a DAC (sorry for the confusion). The SGMII interface that they are using starts on p.91

 

Thanks!

 

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roym
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Registered: ‎07-30-2007

There would be no issue with the termination resistance on the SGMII.  They are set up for 100 ohm lines and so are we.  I believe that is part of the ethernet specs as well.




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583 Views
Registered: ‎07-17-2017

So is there always a termination on the output of the mgt drivers? And it could be 100 ohms across p and n depending on the rcal resistor?

 

thanks!

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roym
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Registered: ‎07-30-2007

There is always termination.  It is 100 ohms after configuration.  The rcal resistor is required to be 100 ohms or very close.  

We are interoperable with any compliant SGMII interface like this so there shouldn't be any trouble at all.  




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