I'm going to design a board with an embedded USB Host connector (managed by Atmel SAM D21 MCU).
I will use that connection only for data communication with a smartphone or a pendrive. I don't need to recharge the battery of the smartphone. Of course, I need to supply the pendrive.
On my board I have to generate a +5V rail only for the USB, but I don't know what is its requirement. Could I use a 100mA regulator? Should I have a 500mA positive +5V rail?
I'm not 100% sure you have a choice. Anybody know for sure?
That rather depends on what will be plugged into it, doesn't it? You should be able to configure the USB host/OTG hardware to negotiate only for whatever current you choose.
For sure the smartphone will detect a USB Host and will use it for battery recharge. Howevere I don't know if this could work with 100mA only (I think 500mA must be negotiated between device and host... and my host could negate the 500mA requirement to the smartphone).
Indeed I specified it: smartphone and pendrives.
So I could live with 100mA only... if my host doesn't let the connected device to require more current... but I'm not sure.
Right. That's the theory.
That just narrows the field. Pendrives can ask for quite a bit; they're getting to be 64 GB and up. Had I not run into pendrives asking for more than 100 mA , I would not have commented :)
Nor am I.
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