SERDES clock generators

[RajanBedi]

For the LS1046, are four external SERDES clock generators necessary to use all of the transceivers.

Four independent clock oscillators will each power-up with different phases and requires more PCB area?

thank you

[mrudangshelat-13]

Hi @RajanBedi,

The reason for using an individual clock for each SerDes clock input is to achieve the input specification mentioned in section# 3.23.2 of the LS1046A datasheet as using the same clock to multiple inputs might create a condition where the input specs of the input clock might not be achieved.

Regards,
Mrudang

[giraffe508]

Hi @RajanBedi 

For the LS1046, it is not necessary to use four external SERDES clock generators to utilize all of the transceivers. You can use a single clock generator with multiple outputs to provide the required reference clocks for the SERDES lanes. This approach will help you save PCB area and simplify the design.

However, it is essential to ensure that the clock generator you choose can provide the necessary frequencies and phase relationships required by the SERDES lanes. You can refer to the LS1046 data sheet and reference manual for the specific clock requirements for each SERDES lane:

• LS1046 Data Sheet
• LS1046 Reference Manual

Here is an example of how you can configure a single clock generator to provide the necessary reference clocks:

 Clock Generator Output 1 -> SERDES Lane 1 Clock Generator Output 2 -> SERDES Lane 2 Clock Generator Output 3 -> SERDES Lane 3 Clock Generator Output 4 -> SERDES Lane 4 

Make sure to follow the guidelines for clock routing and termination to ensure signal integrity and proper operation of the SERDES lanes.

I hope this helps! If you have any further questions, please feel free to ask.

Best Regards,

[RajanBedi]

a single clock generator with multiple outputs isn't easy to find, why can I use a single XO? Could this be used by all the SERDES transceivers?