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I want to use GigaBlox Nano in my board. I plan to add standard magnetics to interface with traditional ethernet devices. I’m familiar with typical PHY topologies, but without knowing about the actual IC used on this board, I’m hesitant to assume. Does BotBlox provide a reference design to connect transformers to each port? Or, maybe the schematic of your RJ45 daughter board?
Absolutely, design files of both daughterboards are open source and available here. We also offer a free design review service, so we can check your schematic is correct to prevent issues before you go to manufacture.
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I just downloaded the library part from snapeda for the GigaBlox Nano. The pinout in the library part compared to the pinout table in the datasheet is off-by-one for every pin. Is that a known issue? I’m assuming the datasheet is correct and the library part has the error.
Specifically, I downloaded the Eagle library using this link: https://www.snapeda.com/parts/BB-GGN-A-1/BotBlox/view-part/?welcome=home
Just checked. This is correct.
On the receptacle side, the pins are mirrored, meaning it is pin 1 on GigaBlox Nano that will mate with 2 on the baseboard. This is the nature of the Samtec LSHM-120-02.5-L-DV-A-S-K-TR header, as it is hermaphroditic and the pins are mirroed.
The footprint and symbol on snapEDA are correct.
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Oh interesting! I see now in the datasheet that it explains what you said. I’ve not used a connector like that before.
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Quick question about the input voltage range of the Gigablox Nano. I’m designing a regulator to power the switch as well as a few other low-power devices. Setting it to 5V would be ideal for the other devices, but I see 5V is the lowest allowable voltage for the Nano. How strict is that 5V lower limit? If there’s a transient that drops down to, say, 4V, will that brownout the switch?
You can take it down to 4.5V, without issue.
Hope that helps!
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Perfect, thank you.
I’m working on my schematic to add magnetics to the PHY of the switch. I’m using your RJ45 daughter board as a reference. Normally I’d expect to have the center tap tied to some voltage on the pin that’s labelled VCC, but it looks like it’s just got a capacitor to ground on there. Does the PHY not require the center taps be tied to a positive voltage?
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Two more questions:
I’m putting two Nanos on a board next to each other and directly connecting them together. For a direct PHY-to-PHY connection, can I directly connect one port on one switch to a port on the other switch? Or should I put series capacitors in line with each trace?
Can I leave the pins of unused ports floating? Similarly, can I leave floating the unused pairs of 10/100 ports?
For a direct PHY to PHY connection between two GigaBlox Nano, yes you would connect them directly. GigaBlox Nano contains a series capacitor on each line, so technically this results in two series capacitors on each connection. However, this does not have any significant impact on the signal, and still works just fine.
Yes you can leave the pins of unused ports floating / unconnected. For the unused pairs of 10/100 ports, yes, you woulda also leave them floating / unconnected.