DS280MB810: Need a suitable switch part for selecting between 1x QSFP28 and 4x SFP28

Vaishak B

Part Number: DS280MB810
Other Parts Discussed in Thread: DS280DF810

Hi team,
I have a SOM which gives out 4 pairs of serdes (USXGMII) supporting 25Gbps per serdes. This can be connected to either 1x QSFP28 and 4x SFP28 to utilise full 100G bandwidth. In my custom carrier board design i want to implement both 1x QSFP28 and 4x SFP28 but select any one interface at a time. Could you suggest me a suitable part that supports this application ?

4 months ago

0 Charles 4 months ago

TI__Expert 8713 points

Hi Vaishak,

Using 2x DS280MB810 (one for mux, another for demux) can work. Please see Figure 9-5 from Application and Implementation section in datasheet (Section 9) .

Alternatively, if your system loss is greater than 20dB, we recommend using a retimer. For this case, you should use 2x DS280DF810.

Best,

Charles

0 Vaishak B 4 months ago in reply to Charles

Prodigy 100 points

Thanks for your suggestion. How do i terminate the rest of the unused pins(4x at MUX and 4x at DEMUX) that are supposed to be connecting between the SoM and the DS280DF810 chip ? Can i ground them through resistor ?

0 Charles 4 months ago in reply to Vaishak B

TI__Expert 8713 points

You can leave unused differential high speed pins floating. DS280DF810 has an internal signal detect block to enable the channel. If no signal is present, the channel will not turn on.

0 Vaishak B 4 months ago in reply to Charles

Prodigy 100 points

Thank you Charles.
I am planning to use 2x DS280DF810.

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DS280MB810: Need a suitable switch part for selecting between 1x QSFP28 and 4x SFP28