A well documented project, and its admirable getting actual open source hardware certification, but I think the design isn't really suitable.
All those separate switching regulators look a nightmare for electromagnetic interference to me, the inductors are unshielded and there is no solid ground plane on the PCB. I would be surprised if USB HS (480mbps) works reliably with this layout. Also, there is no consideration given for ESD protection.
A better design would be to have a single more modern high current regulator/module (the LM2596 [1] used dates from 1999) and use protected high side load switches to supply the ports. These kind of high current supplies are a bit tricky (external MOSFETs etc), so a module might be a good shout, example [2], which might even end up cheaper than having 4 discrete regulators and passives.
Protected load switches detect overcurrent and turn off the output, sometimes with auto-retry. Its getting harder to find them in packages with legs, but the AP22815[3] looks suitable in a TSOT package that shouldn't be any harder to solder than the USB hub IC.
Protected load switches could also allow removal of the microcontroller, as they have a simple high/low enable pin and fault LED, that could connect to a simple slide switch and red/green LED per channel. They also offer nice features like discharging the output capacitors, and reverse current flow protection.
As for the suitability/usefulness of a 3A USB hub, if you try and pull 3A through a USB connector, it will get quite warm, especially if you have a micro USB connector on the other end.
That's exactly why such a project benefits from being open source: someone with enough motivation and knowledge to hack something together do it, then other people with more specialized knowledge make suggestions for improvement.
Issues aren't really a great way to address core architectural questions that effectively say "I think it would be better to start over and build this in an entirely different way".
There are some (small) benefits to independent regulators. A massive rail with high-side switches is a completely different design approach with its own benefits.
The issue would be tagged "wish" or "for v2" and discussed. It can later be referenced when a design for a new release is being discussed.
There are always better ways to handle discussions, but on a github issue on the project's repo is probably better than on a HN thread that won't be linked to it easily.
> As for the suitability/usefulness of a 3A USB hub, if you try and pull 3A through a USB connector, it will get quite warm, especially if you have a micro USB connector on the other end.
Makes one wonder about bypassing the connector entirely and just hard-wiring (short) cables to the board.
USB Power Delivery spec basically requires sane cables to handle 3A safely, which isn't much of a stretch, because final non-PD charging spec requires safety up to 2.4A.
Given that, even if you allow 2.4A or 3A, this is not a consistent load, and the fastest I've seen pre-fast charging (strictly, not including >5V PD, or PD-esque incompatible (and 'illegal') QC 3.0, and also not including OnePlus's Dash micro-pulsed 5V 4A/6A) is 1.8-2A (tested using many devices, on Anker PowerIQ 1.0 and 2.0 chargers, on modern Anker cables), and it does not even remotely spend most of its time at that peak.
As in, you will never see >2.0 amps in actual practice on a sane but high performance charger, even if it negotiates PD 3A; and if you happen to, it most certainly will not stay there very long.
Also, in the interest of completeness, the highest I've seen my 6T's 4A Dash charger is a smidgen over 3, and it has a thinner (but still thicker and heavier than your average Samsung/Apple grade) stock cable than any given Anker cable still in my collection. At peak speed, it never felt anything but room temp.
TL;DR Don't worry. If your cables or connectors are dangerously heating up at 3A, then they should be deemed faulty and replaced.
Based on my past experiences I find that "x" amps of rated charging current often is more of a cap on the total input current.
Samsung devices (this is a Note 5 btw) limit charge current when the screen is on, probably to reduce the heat generated by the device (though I would much have preferred using actual SoC and battery thermistors to dynamically throttle this), but under load the device seems to be able to pull power from the charger as needed. When the screen is off, the battery charges at full current but beyond 80% usually slows down below the rated (Entering CV phase from CC) However, the battery chargers on all devices might be set to lower than 4A or whatever the rating is, and without the system load it won't hit the full input current.
Also note that typically devices (esp. Apple) expect 4.8V or so to keep increasing current draw. Most cables are quite thin and unable to meet this requirement, dropping under 4.7 at 1.5-2A. The charge controller will likely then throttle the current to stay above this threshold.
I have had Anker PowerLine (2?) USB A to Micro B cables that were able to handle 4A (rated 2.4) before falling to 4.85V (tested with 5 port usb charger modified to bypass load side switches so theoretically 12A output). Neither connectors, cable, or other components became hot or warm.
Most other cables can barely deliver 4.76V at 1.7 ish amperes.
This probably correlates with parent comment's experiences.
Anker's PowerIQ circuit seems to be wired to do exactly what you say, and looks like a modern CC/CV PWM LED lamp driver: switches to CV and lowers duty cycle to maintain intended max output once it crosses the voltage threshold (which could indicate a runaway thermal overload).
Apple's designs are baffling to me: the worst cables I've ever seen. Take the newest phone, the 11 Pro, and take their beefiest charger (I think this now comes with the phone? Is this the same one as the current iPad iterations'?)... and compare the stock cable to an Anker Powerline 2 or 3: an immediately visible difference in charge speed; and then do the same with a PowerIQ 2.0 charger w/ stock vs Powerline 2/3: an even BIGGER difference.
All those separate switching regulators look a nightmare for electromagnetic interference to me, the inductors are unshielded and there is no solid ground plane on the PCB. I would be surprised if USB HS (480mbps) works reliably with this layout. Also, there is no consideration given for ESD protection.
A better design would be to have a single more modern high current regulator/module (the LM2596 [1] used dates from 1999) and use protected high side load switches to supply the ports. These kind of high current supplies are a bit tricky (external MOSFETs etc), so a module might be a good shout, example [2], which might even end up cheaper than having 4 discrete regulators and passives.
Protected load switches detect overcurrent and turn off the output, sometimes with auto-retry. Its getting harder to find them in packages with legs, but the AP22815[3] looks suitable in a TSOT package that shouldn't be any harder to solder than the USB hub IC.
Protected load switches could also allow removal of the microcontroller, as they have a simple high/low enable pin and fault LED, that could connect to a simple slide switch and red/green LED per channel. They also offer nice features like discharging the output capacitors, and reverse current flow protection.
As for the suitability/usefulness of a 3A USB hub, if you try and pull 3A through a USB connector, it will get quite warm, especially if you have a micro USB connector on the other end.
[1] http://www.ti.com/lit/ds/symlink/lm2596.pdf [2] https://www.digikey.co.uk/product-detail/en/bel-power-soluti... [3] https://www.digikey.co.uk/product-detail/en/diodes-incorpora...