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Benefits of PLDs to mobile handsets

Posted: 31 May 2012 ?? ?Print Version ?Bookmark and Share

Keywords:mobile handset? tablets? battery interface? FPGA?

The pace of innovation in the mobile handset industry has never been higher, with users increasingly demanding more from these devices. Smart phones, tablets and other battery powered devices have evolved beyond communication devices and now offer personal assistance by unifying "always connected" features such as navigation, email, phone, Internet access and camera. Choosing between the two leading smartphone operating systems, smartphone designers depend on their physical hardware to differentiate their products and position them against competitive products. This is an area where programmable logic devices add direct value by providing mobile handset system architects a way to quickly innovate and add new functionality to their products. Below are some examples of why and how low cost, low power programmable logic devices are successfully adding value to mobile handset design.

Asynchronous product development cycles
Readers of this article may not be surprised to learn that the product design life cycles of mobile handset and chipset vendors are fundamentally different. It is fairly common to see new phone models being introduced every other month, while chipset vendors release newer versions of their chipsets in a much slower product cycle cadence. While there are solid and obvious reasons for this, the challenge faced by handheld system architects is also real; i.e. keeping up with product innovation cycles that are faster than what the chipset vendors are capable of supporting. A good example of this is the recent announcement of the MIPI battery interface (BIF) standard.

MIPI battery interface standard
The use of dual-core and quad-core processors, along with the marketing imperative to create a compelling user experience, increases power consumption that has direct downstream effects on power delivery, battery life and longevity. Striking a balance among optimal power delivery, battery capacity, chemistry, safety, and form factor is a significant design challenge. The communication protocol established by MIPI-BIF provides a method for system designers to read parameters on demand to optimize power consumption during device use and to optimize battery charging. It also provides a method to authenticate batteries for systems that need to ensure user safety. Although the MIPI standard has already been announced, chipset vendors will still need time to adopt this standard in their products. However, handset designers may want to take advantage of MIPI-BIF much sooner. Programmable logic devices are perfectly suited in such situations, because they enable mobile system architects to adopt new standards using existing chipset or application processors. In fact, soon after MIPI released the BIF standard, Lattice Semiconductor announced its support for the standard and that it is engaged with key customers on implementing it.

Figure 1: Using a low power FPGA to implement new standards.

Figure 1 illustrates the use of a low cost, low power FPGA to create a bridge between an existing application processor and the recently released MIPI-BIF standard. Communication over the BIF battery communication line (BCL) is enabled using the low power FPGA. On the application processor side, I2C, because it is commonly available, is a natural choice to connect the host application processor to the FPGA. A simple protocol is defined on top of the I2C standard to communicate between the host and the FPGA.

If needed, the host interface can be easily customized using the FPGA solution. In addition, further customization of the BIF interface / protocol can also be achieved when using an FPGA. Furthermore, the FPGA offers the flexibility for customers to even integrate other functions within the same low power FPGA device. By using a low power FPGA as a companion chip to the application processor, handset manufacturers can enable cutting edge features / standards into their products on demand to create clear product differentiation.

Loss of flexibility
Although system-on-a-chip and holistic integration are the mantras of most chipset manufacturers, chipsets are often designed to meet broad market needs and therefore may not support certain standards. This denies handset system architects valuable flexibility. Also, as new standards are adopted by chipset manufacturers, they often completely drop older ones from their portfolio. This again takes away valuable flexibility from both the system architect and the component procurement teams of handset manufacturers. Often in such cases, system architects may want to use the latest chipset solutions based on their merits, while the procurement team may wish to continue using certain older standards, even if not supported by the latest chipsets, to provide supply flexibility. Here again FPGAs provide considerable value.

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