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Comment by numpad0 | Hacker News Reader

Looks so cool! Just one question: IIUC, linear voltage regulators works by wasting voltage delta until target voltage is attained, instead of switching output current as buck converters do, so at 12V input it dissipates heat of up to (12-3.3)[V] * 0.8[A] = 6.96[W] onto the board depending on downstream current draw(of an FE switch, so I imagine would be tiny fractions of 0.8A realistically). Do board feel cool enough to touch as is?(please use back of hand/finger if unsure)

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Hello, yes. Unfortunately it is hot to the touch. The board doesn’t draw 800mA, but it does get to like 60C. Max, the main designer for V2, said a heatsink is recommended. Our thermal via solution keeps it within somewhat safe temps. We wanted to keep the cost low, so we opted for the LDO. In our robot we do direct 3.3V with a buck that does 3.3 for our entire system. That’s Max’s power board.

Don’t be afraid to implement a basic buck converter! Something like the MPQ4572 isn’t too hard to get right (right enough for hobby projects at least).

They made an Ethernet board, I don't think a buck converter would be hard for them, but, as they said, it does increase the cost.

Honestly, hooking up a simple Ethernet switch IC is a cool project but isn’t especially difficult - and this is only 100 Mbps also so not very tight tolerances.

Set up your design rules right and I’ve had gigabit RGMII and 1000Base-X work first try.

Yes, if you're an expert at designing PCBs, I'm sure it's not hard. It's objectively hard, though.

For sure, this wasn't that hard. But I think that's great; it means anybody can be an EE. That's a core mission of our team. Our team works hard on PCIe 4.0, USB 3.1 Gen 1, and Gigabit ethernet as well. This is just one board that we made and were proud of. Feel free to take a look at our other boards in the documentation website!

how hard do you find pcie v4? did you look at how big a step is it to v5?

I would think the majority of people would be running this of of 3.7-4.2V lithium batteries or 5v USB so the step down Delta would be minimal, but yeah probably good advice to incorporate a more efficient buck step down for those running traditional 12v systems which usually operate at 14.4v.

Thanks - yeah 60C(140F) sounds somewhat warm, glad you're already planning for a DC-DC upstream. Feeding it 5V could make sense too(3.3V out + 1.2V dropout = 4.5V < 5V), but anyway this project feels like scratching an itch for many. Congratulations to you and your team!

It may be beneficial to have an additional system power rail. Adding 5V produced by an efficient buck converter would allow for more efficient LDOs on the small boards.

LDOs are much smaller and don't produce noise like switch mode power supplies. It's true you will waste some power but that can be minimized by making the dropout voltage as small as possible.

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