ULPI Transceivers in Bus Power Application

Hi Everyone,

I started a new thread to address USB in bus powered application using ULPI.

As I understand the idea of ULPI, the ULPI PHY is helpful when interfacing processors and FPGAs without built in USB support.

In my current application, I am using an SMSC USB3318 but obviously there are many others.

If we assume that the companion processor/fpga acting as a USB controller is not low power, then how could we use the ULPI PHY to control power?

The PHY is designed to meet all the current management issues including suspend current. The catch is that as far as I understand things, the ULPI PHY is also dumb without a controller. This makes it a chicken/egg problem. I think you need the controller running to manage everything, and if the controller draws power, I'm not sure how you can manage suspend current and possibly 100mA before enumeration. Many DSPs, FPGAs and fast MCUs draw too much power, and ironically, these are the type of devices that can actually put higher data rates (USB high speed) to good use.

I see in some of the bullet points on data sheets that the ULPI PHYs are supposed to be good for bus power applications but I haven't seen anything like a discussion or application note supporting this idea.

So does anyone have any clever ideas? I'm sure this problem is common.


Al Clark

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Al Clark
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m. I





How often do you run it in active mode? If not too often, you can perhaps charge a battery during standby. My Android phone runs at

600MHz and draws only 250mA active and much less than 100mA startup. It can certainly meet the USB spec.
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