DS125DF410: Questions on lower Data Rates for DS125DF410 and retimer acceptance of CML or LVPECL

Alex Scott

Part Number: DS125DF410

Posted for a customer by Alex Scott...

The data rate for XGS-PON is 10G+ . The Data rate for GPON is 2.5G. My question is as follow

1) Dose DS125DF410 support lower data rate such as 1G and 2.5G

2) The data sheet show that the input is CML. For my application, XFP port can support either XGS-PON or GPON optical module. For XGS-PON, the output from optic is CML. For GPON, the output from optic is LVPECL. Can the re-timer accept either CML or LVPECL. We need to AC couple the signal. Do you have recommend AC couple termination scheme that work for both CML and LVPECL?

over 8 years ago

0 Dan Kisling over 8 years ago

TI__Expert 6195 points

Hi Alex,

1) It depends by what you mean by 1G. The DS125DF410 is able to support 1.25Gbps and 2.5Gbps data rates.

2) I believe this document might be able to help for LVPECL to CML. http://www.ti.com/lit/an/scaa056/scaa056.pdf Check out page 6 “AC-Coupling Between LVPECL and CML”

Regards,

Dan

0 Hayden_Hast over 8 years ago in reply to Dan Kisling

TI__Intellectual 1515 points

Hi Dan,

Thanks for the response, the app note was helpful. I'm working with Alex on this project.

Regarding the app note, looking at figure 5. Would it be possible to use one termination (figure 5) for 2 different applications? Application 1 is LVPECL to CML AC couple, and Application 2 is CML to CML AC couple.

Thanks,
Hayden

0 Hayden_Hast over 8 years ago in reply to Hayden_Hast

TI__Intellectual 1515 points

Hi Dan and Team,

Any update here?

Regards,

Hayden

0 Dan Kisling over 8 years ago in reply to Hayden_Hast

TI__Expert 6195 points

Hi Hayden,

I suppose that you could look at the spec of the output driver on the CML and LVPECL devices and see if there is a biasing network that could satisfy both outputs from a common mode voltage perspective. In order to solve that math problem you would need to know the specifics of your devices.

It would seem to me to make more sense to make two networks, one for CML to CML and one for LVPECL to CML and use a MUX to switch between them. After all, you can only use one data path at a time.

Regards,

Dan

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DS125DF410: Questions on lower Data Rates for DS125DF410 and retimer acceptance of CML or LVPECL