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Maximise general-purpose USB 3.0 device controller

Posted: 30 Jan 2013 ?? ?Print Version ?Bookmark and Share

Keywords:USB 2.0? 3.0? HD movie? real-time operating system?

Since its introduction in 2000, USB 2.0 has been the de-facto interface standard of the PC realm. With a transfer rate of 480Mbps, it is lightning fast and served as an apt solution for many interfacing needs. However, with the rise in demand for higher data rate applications like HD video streaming and high capacity hard disks, the reign of USB 2.0 is slowly being replaced by its successor C USB 3.0.

In communication world, faster is always better. With USB 3.0, 10 times faster data transfers are within reach. With a signalling rate of 5Gbps, SuperSpeed has dawned as a 'Fast Sync and Go' Technology. Thanks to SuperSpeed, users can copy a HD movie of 25 GB in just 70 seconds compared to 13.9 minutes at High Speed. This means no more waiting for consumers.

The enhancements to SuperSpeed USB are not just higher data rates but also include improvements in overall interactions between devices and a host computer. One of these enhancements includes customised power distribution.

USB 3.0 ensures sufficient power is provided to devices when required. 50% more power is provided for unconfigured or suspended devices (150mA up from 100mA). 80% more power is provided for configured devices (900mA up from 500mA). This means that more power-hungry devices like hard disks and displays can now be configured as bus-powered devices.

Another impact of increased current sourcing is faster battery charging. Since USB 2.0, there is an increased trend in charging portable devices through USB VBUS. Even though this is a handy feature, it required much time to charge a device over USB 2.0. With USB 3.0 featuring 900mA configured current sourcing, devices can now charge in half the time than what is required when using USB 2.0. For comparison, consider a 1400mAH battery and assuming 90% efficiency. With USB 3.0, the battery can be charged in 1 hour 44 minutes compared to 3 hours 6 minutes on USB 2.0 systems.

Power efficiency is another key enhancement of USB3.0. To eliminate wastage of power, checks are done at various levels of the USB 3.0 hierarchy. Link level power managements ensures that the host computer or device can initiate a power saving state when idle. Now links can progressively enter lower power states when link partners are idle. Continuous device polling no longer exists.

PC market forecasts confirm the outburst of USB 3.0 host and devices is yet to happen. With certification of the NEC host controller by the USB-IF, more and more PCs are now equipped with USB 3.0 technology. One major challenge lies in the development of multitude USB peripherals that are yet to hit the market. If USB 3.0 peripheral controllers available in market are adaptable to the design of any end application, faster market adaption is possible.

Figure 1: USB 3.0-image sensor interface.

Typical applications for USB 3.0
USB 2.0 with its speed of 480Mbps provides sufficient bandwidth for many applications. However, with the rise of HD video and high-resolution cameras, there has been a leap in the multimedia world, which will be bottlenecked by the lower throughput of high speed USB. SuperSpeed USB with throughput up to 5Gbps can help in these scenarios.

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