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I am designing an Linux Board which needs a SATA connector.

Now im faced to choose between 2.5 HDD SATA connectors and the new mSATA (mini PCI express) connectors.

For compatiblity and usuabillity purposes, i would like to use or foreseen both of them in the design. So that i can choose during production which one i would like to have soldered.

Now the important question:

As i know, SATA is a more cricital Data Interface. It has to be an impedance controlled differential line. What is the best practce to connect these two footprints on my board?

My first idea was: CPU ---> Con#1 -[0R Res]------> Con#2 What do you think about that? I would use the 0-Ohm Resistor, because otherwise there is a Stub from Con#1 to Con#2 and this would produce reflections and impedance missmatch wich resulst or can result in a ringing Dataline.

Whats the best practice to solve this problem?

Thank you!

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  • \$\begingroup\$ Thanks. My mSATA connector is too small. Therefore i cannot overlap it... But overlapping would also result in a Stub on the trace. so this is also not a good solution... \$\endgroup\$
    – C. Hediger
    Commented Jul 27, 2015 at 12:13
  • \$\begingroup\$ There also seems to be both mSata -> Sata and Sata -> mSata adaptors available commercially. Wouldn't that be an alternative? \$\endgroup\$
    – Passerby
    Commented Jul 27, 2015 at 12:18
  • \$\begingroup\$ Hi Passerby, thank you for your comment. I have also seen such adaptors. But i think it would be much better to support mSATA or SATA directly without the use of any adaptors. Cause i want to mount the HDD or the SDD onto the Board. if there is a need for any adaptor, i cannot guarantee, thet all holes will be at the right place, because i think every adaptor is different to the other. \$\endgroup\$
    – C. Hediger
    Commented Jul 27, 2015 at 12:24
  • \$\begingroup\$ Is this for SATA 3.0 Gbps or 6.0 Gbps? I think mSATA is not so popular. There is also the M.2 connector -> en.wikipedia.org/wiki/M.2 \$\endgroup\$
    – Paebbels
    Commented Jul 27, 2015 at 12:37
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    \$\begingroup\$ Hi Paebbels. It is for 1.5Gbps SATA. Yes i know the M.2 connector. But for the first series, we would like to use the mSATA connector and, as written, the regular SATA connector. \$\endgroup\$
    – C. Hediger
    Commented Jul 27, 2015 at 13:08

1 Answer 1

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Those solutions may work, especially if carefully evaluated. Make sure that the impedance mismatch at the resistor bridges is acceptable and you do not solder the first connector at all, if you add the resistors.

Something that may work even better are cuttable traces. Use CON#2 by default, but replace the resistors with standard traces. Once you switch to CON#1, cut the traces manually. If you are not able to produce a separate PCB for that, I assume that you produce an acceptably low amount of PCBs to justify the cost for that.

An alternative, that may not be necessarily better, adds some cost, but is also more flexible, would be to use a switch:

With that solution, you could use both ports, without ever having to change your process.

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