USB port power limits

How much power can the Reform USB ports output? 5v @ 500mA? or more?

Checking out the schematic (Reform 2 USB Power sheet), USB ports receive power through an AP22815 power switch and a TPS2561 port power switch from the system 5V rail.

The Reform 2 Regulators sheet mentions that up to 5A can be supplied on the 5V rail.

The AP22815 mentions up to 3A output current. The TPS2561 has a maximum continuous current of 2.5A with an adjustable current limit. The limit is set by the resistor connected to the ILM pin on the TPS2561.

The schematic shows a 24.9k resistor which sets the limit around 2A if I read “Figure 10-5. Current-Limit Threshold vs RILIM” right.

So, the maximum for any single USB port seems to be 2A, the two ports connected to a power switch (USB_3_1 and USB_3_2 as well as USB_3_3 and USB_3_4 although I’m not sure which ports these are) are limited to 2.5A together and all USB ports are limited to 3A.


Thanks! Very thorough answer. I was mainly just curious if a Moonlander keyboard could be powered through one of the USB ports if the RGB lighting was on. Seems like it will be able to.

I don’t envision that happening often, as I imagine the keyboard on the Reform is one of the bigger selling points that I’m very much looking forward to.