I have a problem with one of my designs, I've made it so that the board can power up from the USB connector, the problem is that the board struggles to boot.
I guessing this is because the PC is limiting the USB output to 100mA, and the USB is interfaced straight to the uP in the design (that would have to negotiate more power) - but that hasn't booted to do that as the board is struggling to boot! A vicious circle!!!
This whole thing has been made worse by adding a PTC polyfuse in line with the USB 5V coming in, the series resistance of that is causing voltage drop into the main regulator.
Does anyone have any experience of doing similar things with USB powering? I'd like to keep the protection if possible.
Thanks,
G
I guessing this is because the PC is limiting the USB output to 100mA, and the USB is interfaced straight to the uP in the design (that would have to negotiate more power) - but that hasn't booted to do that as the board is struggling to boot! A vicious circle!!!
This whole thing has been made worse by adding a PTC polyfuse in line with the USB 5V coming in, the series resistance of that is causing voltage drop into the main regulator.
Does anyone have any experience of doing similar things with USB powering? I'd like to keep the protection if possible.
Thanks,
G