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USB Embedded Master: requirement on power supply?

Started by pozz July 27, 2016
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?
pozz wrote:
> 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.
I'm not 100% sure you have a choice. Anybody know for sure?
> 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?
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. -- Les Cargill
Il 27/07/2016 18:31, Les Cargill ha scritto:
> pozz wrote: >> 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. > > I'm not 100% sure you have a choice. Anybody know for sure?
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).
>> 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? > > That rather depends on what will be plugged into it, doesn't it?
Indeed I specified it: smartphone and pendrives.
> You > should be able to configure the USB host/OTG hardware to negotiate only > for whatever current you choose.
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.
pozz wrote:
> Il 27/07/2016 18:31, Les Cargill ha scritto: >> pozz wrote: >>> 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. >> >> I'm not 100% sure you have a choice. Anybody know for sure? > > 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). > >
Right. That's the theory.
>>> 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? >> >> That rather depends on what will be plugged into it, doesn't it? > > Indeed I specified it: smartphone and pendrives. >
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 :)
> >> You >> should be able to configure the USB host/OTG hardware to negotiate only >> for whatever current you choose. > > 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. >
Nor am I. -- Les Cargill