There's been a lot of talk about how the system-on-a-chip will replace the traditional way of manufacturing individual semiconductors. Some industry experts believe it's only a matter of time before companies like Fairchild, a supplier of high-performance semiconductors, will have to conform to the SoC way of doing business.
Despite this popular mantra, it's unlikely we'll ever see a truly complete system-on-a-chip. The term implies that it contains a complete system on one chip. However, there are two major issues that can't be incorporated into the single-chip solution: the power supply and the ability to isolate the chip from the outside environment. To be more accurate, system-on-a-chip should be called "multiple-functions-on-a-chip."
What exactly is a system-on-a-chip? A typical SoC design has a CPU core, memory and memory controller, power management, graphics, standard-cell logic, USB or Ethernet-type interface, and an MPEG administrator. Semico Research Corp., Phoenix, suggests that the SoC needs to be fabricated on a 0.35-micron or 0.25-micron or smaller geometry process, with greater than 500,000 gates, and be contained in a high-pin-count package.
This raises integration issues inherent with the SoC design.Design cycles are getting shorter and shorter for OEMs. It's common to introduce a new product every nine months, although in some markets, new applications are generated every four months. Design cycles for multifunction chipsets are generally eight to nine months, excluding redesigns. Intellectual property reuse may shorten that cycle, but it's doubtful that the SoC design cycle time will be able to keep up with the rate of next-generation applications.
Costs represent another substantial issue. Smaller geometry processes are more expensive when compared with legacy processes. To produce multifunction chipsets requires system and application expertise, with the development costs passed on to the customer as a nonrecurring expense. While the intellectual property can be reused or purchased from a third party, it also adds to the overall end- product cost.
Other issues that affect the development of a true system-on-a-chip are:
- The requirement for functions and enhancements to be added to the end application after the design is complete to make the product more competitive.
- Retaining power supplies as discrete components to handle the heat generated by these types of devices.
- And the isolation of the chipset from the outside environment to protect it from the electrostatic discharge inherent in silicon devices.
The SoC was intended to integrate on a single chip all the functions needed for specific applications. In reality, it has driven an increased demand for high-performance building block chips to support the SoC functionality. Companies that supply these supporting components have seen an increase in demand for their products with the development of the so-called system-on-a-chip.
Generally, when a SoC is designed in, there are six to 15 separate building block components supporting it to enable the full functionality. Instead of eliminating the need for discrete components, the SoC phenomenon actually drives the requirement for building block semiconductors.
The continuing evolution of applications, integration of more functions, smaller geometries and more advanced technologies will keep the SoC from truly becoming a one-chip solution and will ensure the growing need for high-performance building block semiconductors.
W.T. Greer is senior vice president and general manager of the Interface and Logic Group at Fairchild Semiconductor International, South Portland, Maine. Address comments to EBNletters@cmp.com