The USB 3.0 Promoter Group is working on a new specification to significantly extend the power capabilities of the Universal Serial Bus 3.0 standard. The goal is to enable a new generation of USB 3.0 cables and hubs to deliver up to 100 watts of power to PC 
peripherals while maintaining compatibility with the USB battery-charging 1.2 spec and USB-powered applications already in use.
Founded by Hewlett-Packard, Intel , Microsoft, Renesas Electronics, ST-Ericsson and Texas Instruments, the USB 3.0 Promoter Group hopes to build on the rapidly increasing industry momentum for using USB power to charge a broad range of mobile devices, noted Chairman Brad Saunders. He is also a senior mobile systems architect at Intel.
"The new USB power-delivery specification extends USB's cable power-delivery capabilities beyond simple battery charging," he said. "For example, charging the battery of a notebook PC -- or simply powering that notebook PC while actively using the USB data connection -- would be possible. Conceivably, a notebook PC could rely solely on a USB connection for its source of power."
Delivering 100 Watts
Formalized in 2008, the USB 3.0 standard features transmission speeds of up to five gigabits per second, 10 times faster than the previous USB 2.0 standard. Moreover, the currently available power spec for USB 3.0 is capable of handling a unit load of 150 mA -- a 50 percent boost from USB 2.0.
The new USB 3.0 power-delivery standard now in the works would enable power-hungry peripherals such as LCD displays and high-speed external hard drives to be powered directly from a compatible USB port or hub. Power also could be supplied in either direction without having to change the cable.
The USB 3.0 Promoter Group said Wednesday that a pre-release industry review of the new spec will be provided at the Intel Developer Forum in San Francisco next month. "Our intention is to essentially complete the technical work of the specification by the end of this year, which should map to making the specification broadly available during the first quarter of 2012," Saunders explained.
If everything proceeds according to plan, the new USB power-delivery spec would effectively become available to hardware developers for implementation in future products sometime early next year. Still, consumers shouldn't expect to see the benefits of the new technology for some time thereafter. Though the USB 3.0 standard was formalized in November 2008, the first consumer products based on USB 3.0 didn't arrive until early 2010.
Cable and Hub Upgrades
The group's USB 3.0 power-delivery spec will be compatible with existing cables and connectors and work equally well with both USB 2.0 and USB 3.0. However, consumers will need to upgrade their existing USB cables and hubs to take full advantage of the maximum power-load capabilities of the new technology, Saunders observed.
"Delivering power per the new power-delivery specifications will require changes in the VBUS power circuits of power providers and consumers; existing USB hubs are not designed to deliver 100 watts," Saunders said. "Existing cables will be limited to a power level much lower than 100W -- more likely somewhat closer to the existing battery-charging spec limit of 7.5W."
For higher power levels, newer cables that are detectable by the new VBUS power circuits will be required, Saunders observed. "These newer higher-rated cables will be backward compatible for existing USB uses," he added.
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