One of the main problems we’ve faced with USB so far has been the lack of electrical power available through the bus itself.

Technically, USB2.0 can supply up to 500mA at 5VDC through each port but as the demand for speed and simply connectivity grows, the bus itself hasn’t had enough juice to keep up with demands.

The other problem has been all of the whacky useless add-ons that have been invented for USB – everything from cup warmers to vaccum cleaners and the rest.

The problem with most of these devices though is that they don’t behave and use the USB bus correctly. They don’t negotiate correctly to set the correct power consumption. I’ve heard of plenty of tales of USB ports being burnt out by bad devices. I’ve been given a massage ball that when I plug into the USB port, resets the computer!

USB3.0 looks like it will address some of these issues – at least in terms of power it can supply. Most of the new USB3.0 capable motherboards are claiming a 3X power output boost compared to USB2.0. In reality, the maximum current drain allowed is 1.8amps in the new battery charging specification within USB3.0.

This mode is enabled by shorting the two data pins – D+ and D- – together with a resistance of less than 200-ohms. That’s a significant improvement over the 500mA max of USB2.0.

The way power is apportioned too has been changed.

USB2.0 had a unit load current of 100mA. USB3.0 bumps that up to 150mA. USB2.0 can handle up to five unit loads whereas USB3.0 can handle six. That automatically pushes up the maximum load current during data transfer up to 900mA. This should have a significant impact of battery charging times for new devices such as the iPhone 4, which, hopefully, has been designed with USB3.0 in mind and not USB2.0.

We’ll have to wait until July for that.

Still, the changes will make it easier for notebooks and motherboards to supply sufficient power to external devices into the future.

Of course, powering USB3.0 devices at this sort of current level on battery power will see battery life shrink at a massive rate. It won’t take long to flatten a notebook battery if it’s pumping out 1.8amps through its USB3.0 port!

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