RealTime IT News

The Magic of CMOS Chip Sets

Marvell Semiconductor, Inc., a subsidiary of Marvell Technology Group, Ltd., recently announced that it had completed development of one of the first all-CMOS (complementary metal-oxide semiconductor) 802.11b chip set solutions (RF transceiver and baseband processor). The article correctly identified that one of the profound impacts that CMOS technology will have on the 802.11 industry will be substantially lower production costs.

An equally, if not more important aspect of CMOS technology that bears discussing is it's impact on the technology of chip sets, and 802.11b chip sets in particular. CMOS is a technology process that is used to develop the transistors that go into most of today's microchips. It uses silicon and manipulates it in such a way as to create a 'current gate' as a means for electrical control. The key differentiating factor that makes it so exciting for 802.11b chip sets is that it uses almost no power when it is not needed. That may not be so important for computers using AC power supplies but it is a leap forward for battery-voracious mobile devices including laptops, PDAs, and phones.

Bill Windsor, Director of Product Marketing at Marvell, said that while he didn't have hard data immediately on hand to support the power consumption differential he could give us anecdotal evidence. When a laptop that usually had four hours of normal battery life was tested with a standard (non-CMOS) 802.11b PCMCIA card, the battery life plummeted to just forty minutes! I'm no good at math but I'd say that is an incredibly significant difference.

The result of the CMOS process in the production of things like 802.11b chip sets is remarkably lower power consumption and low heat dissipation. The reason for this is that the resultant negatively and positively charged transistors only draw power when switching polarity.

Another important aspect of the CMOS chip set developed by Marvell, said Windsor, is that the product has a "small board size." Inherent size limitations of mobile devices make this a key advantage that comes from the integration of chip functions that used to require at least five separate chips according to Windsor. Marvell's all-CMOS chip set solution takes those functions and integrates them into its CMOS-based chip set.

Functions that are integrated into one chip on the Marvell 88W8000 RF Transceiver include: power amplifier (PA); low noise amplifier (LNA); variable gain amplifier (VGA); voltage-control oscillator (VCO); programmable frequency synthesizer; and RF up/down converters (mixers). These functions alone are typically implemented in as many as five chips.

The Marvell 88W8200 baseband processor works with the RF IC to provide a complete physical layer solution for 802.11b. It enables the recovery of weak and distorted signals and reduces overall power consumption. It incorporates advanced antenna diversity control, enabled stations to select optimum-receiving antenna. An advanced DSP engine conducts real-time multi-path signal analysis, acting to suppress reflections and distortions to achieve highest available signal clarity and maximized bandwidth. Marvell also stated that its chip set solution does support a high-performance 22 Mbps mode.

Chip set architecture wonderments aside, the most important factor that makes all-CMOS chip sets so desirable for 802.11 solutions is their reduced power consumption. That technology advance could make all the difference in the perceived usefulness and robustness of future wireless devices operating on wireless LANs.

Matthew Peretz is Managing Editor of 802.11-Planet.com