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I am designing a base board PCB for CM3+. According to the datasheet the processor used is BCM2837B0 which is the same as Raspberry pi 3B+ LAN7515 chip is used in raspberry pi 3b+ which is 1000 base ethernet But LAN7515 is not for sale anywhere also cannot find the datasheet Now I can use LAN7500 which is 1000 base but doesn't have USB downstream or LAN9512 which is only 100 base.

Do I have any option which is 1000 base and has usb downstream?

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I've looked for a similar chip, and actually got in touch with Microchip - the sales rep said they didn't even know about the LAN7515. It must be a special IC made for the Raspberry Pi Foundation - certainly their volumes are high enough to justify this. As far as I'm aware, there isn't a GBE + USB hub single IC available. Practically, however, I've found using a USB251x + LAN7500 is cheaper and much easier to route on the PCB than using the LAN951x ICs.

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  • I'm doing the same as punyanagari. I'm chosing the chips now, but I don't need the gigabit functionality. What's hard about the LAN951x IC's that you prefer two chips over one (cost is not the issue for me here) ? – lode Apr 24 at 19:31
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    @lode There's nothing wrong with the LAN951x chips, but the routing is a bit nasty. Have a look at the pin out - with the downstream USB ports at the top, going clockwise you then have the osc input, then the upstream USB port, then the RX/TX ethernet pairs. This means you probably have to route the diff pairs on both sides of the board to get a reasonable layout. I prefer to run the diff pairs on a single side, unless I'm really space constrained - no ref plane crossings etc. – awjlogan Apr 24 at 19:52
  • I'm a warned man :) – lode Apr 24 at 20:44
  • Hi both which GPIO did you use for RESET OF LAN chip? How did you configure it in the dtb? – punyanagari May 25 at 14:59
  • @punyanagari Suboptimally, I just used an RC (10 K, 10 n) on the reset pin. For production, something more robust would be good... – awjlogan May 26 at 9:41

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