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USB is the most widely deployed digital wired connection interface on PCs, mobile phones, printers, digital still cameras (DSCs), portable music players, monitors, and other digital consumer electronics products. USB is also a standard communication channel in most of the medical and industrial applications USB allows consumers to easily establish high-speed connection between products to transfer data or multi media content such as photos, videos etc., To address the increasing popularity of the USB in all the above mentioned markets, the ULPI specification were developed.

Announced on March 1, 2004, the ULPI specification provides a low-pin, low-cost, small form-factor transceiver interface for any USB application 

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Designers all over the world are faced with increasing pressure to design smaller products, in less time, and at lower cost. At the same time, as smaller deep sub-micron processes are introduced, integrating the physical layer analog circuitry required by technologies such as USB and On-The-Go is a task that has become a technical challenge, requiring more man-hours, more investment, and more silicon spins.

To get a product to market faster while keeping costs low, the physical layer can be provided in a separate chip. The designer integrates the bulk of the USB digital logic into the ASIC in a very fast time, and connects it to an external PHY that is proven and already available on the market.

ULPI was developed by a group of USB industry leaders to address the need for low-cost USB and OTG PHYs. Existing specifications including UTMI and UTMI+ were developed primarily for Macrocell (IP) development, and are not optimized for use as an external PHY. Using the existing UTMI+ specification as a starting point, the ULPI working group reduced the number of interface signals to 12 pins, with an optional implementation of 8 pins. The package size of PHY and Link ICís are drastically reduced. This not only lowers the cost of Link and PHY ICís, but also makes for a smaller PCB.

With ULPI specifications version 1.1 released on October 20,2004, the ULPI promoters group agreed to freeze the specifications. The specifications are freely available under  Documents section of this website.