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?
USB Embedded Master: requirement on power supply?
Started by ●July 27, 2016
Reply by ●July 27, 20162016-07-27
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
Reply by ●July 28, 20162016-07-28
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.
Reply by ●July 28, 20162016-07-28
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