Electronic – SATA 2.0 to M.2 (NGFF) design

layoutsata

I am designing a PCB with a A20 (allwinner) SoC. This SoC has a SATA 2.0 host (RXP RXM TXP TXM) that I have to route to a M.2 "M" key connector.

  1. I found only one source for pin out, but I can't find confirmation of this pinout. Anyone can confirm if this is correct? I should connect only the 4 data lines, GND and 3.3V pins from the list there right?

  2. Should RXP RXM TXP TXM be controlled in impedance and if so what is typical value for them?

  3. What is the dimensions between the NGFF connector and the screw hole for 2230, 2242 and other formfactors? I guess the screw hole position in each formfactor is a standard to enable compatibility, same as screw hole position on the motherboard. However I can't find this information anywhere. I asked NGFF connector manufacturer but had no reply so far…
    I know 2242 stands for 22mm wide 42mm long, but is 42 mm the total dimension of the board, or dimension to the screw hole? And from what point? Center of the connector? End of connector? End of the 2242 board?

Best Answer

So I finally came with the solutions :

  1. I checked on some boards to see if it matched and it does.

  2. Got feedback from Allwinner engineer, differential pairs should be controlled to 100Ohms +-10%

  3. I found that the screw hole center on the NGFF PCB matches the edge of the PCB. And it's exactly at 42mm (for 2242) from the other PCB edge. So in order to put the screw hole on the host PCB I checked the connector drawing to find out where the NGFF PCB starts compared to the connector layout. Then added 42mm.

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