I'm working on a project that has a USB port connected to to a PIC32MX460F512L. The 5v for the USB is currently coming straight from the VREG. The port is only designed to accept USB flash drives, but it occurred to me that someone might decide to plug in a higher power device. I'm using a linear 5v regulator in my design, and it will definitely overheat if a device tries to draw say 2A from the USB port.
If something besides a flash drive is plugged into the port, I don't care if it charges, or functions. I just want to make sure neither the device nor my circuit will be damaged.
Here's some options I'm considering.
- Use a dedicated protection IC. for example: AP21510FM-7
These look perfect, but I can't find any that will limit the current to less than 400ma. That's still too much for my reg so I would have to move to a switching regulator.
Use a simple resistor. Would that work?
Use a PTC with a load rating just above whatever flash drives typically draw.
This is kind of crude, but it should at least protect my VREG.
- The most likely device that could be plugged in will be a cellphone I think. I know there are some standards for resistors on the datalines setting the current capacity. So will phones even try to charge from this port? All I currently have on my data lines is a TVS.