xem6010 buss powered


I’m intending on using the XEM6010 in buss powered mode— similar to what people have done with the XEM3010 (keeping in mind the USB 2.0 maximum of 5 unit loads - 500mA). Now I’m assuming that on power up the XEM3010 initially uses 1 unit load in line with USB 2.0 spec and then once configured becomes a high powered device by requesting the full 5 unit load. Will the XEM6010 do the same and become a USB high power device after configuration (requests 500mA)


The firmware on the 3010 and 6010 are identical.

Thanks, thats good news. So I can assume that if I plug the XEM6010 into a USB host that is able to deliver 5 unit loads (the full 500mA) then my design is limited to 2.5W.

Well, actually… The XEM6010 (and, in fact, all our devices with the exception of the XEM3001/XEM6001) are intended to be self-powered. Most of these devices will consume more than 2.5W if they are loaded with even moderately complex FPGA bitfiles.

And, really, most USB hubs don’t really pay much attention to the USB power information anyhow. It’s more of a formality.

Ok… I see your point.

To clarify my intentions with the XEM6010: In my design the USB buss power will be passed through a smart switch current limiter and super cap charger to garantee no more than 500mA (or possibly less) is available to the device. The fpga configuration will not be to thirsty but will produce transient loads (High Speed Deserialisation and the like) possibly larger than 500mA scattered amoungst durations of idle time (where the XEM6010 load is reduced where possible). The average load will be below the USB2.0 limit - evened out by the large bucket (super cap with energy management harware and software fluff)

I have built a couple of prototypes with your XEM3005 and proved the concept and then I started reading the USB2.0 spec details before putting the XEM6010 project into copper and got bogged down with the USB power regulations…

Your XEM6010 consumes 117mA (when I measure it) without any config loaded in the FPGA. So the load is close enough to 1 unit load on power up which ticks the USB 2.0 spec.

If I limit the XEM6010 load to 500mA all should be ok on any host that can provide the high power spec. If the USB config bits don’t enumerate to a “high power device” (demands 5 unit loads) odd things are likely to occure on any unsuspecting low power USB2.0 port.

I’m wondering if it’s possible to alter the USB configuration in the Cypress chip or even just check to see what the config bits are after enumeration (regarding the power information). Is there an easy way to check this?

Am I wasting my time worrying?