Abstract :
Mobile power or portable power is typically defined as battery cell operated. An important requirement is the operation from various portable energy sources. This requirement is driven on the low end by operation from a single cell 1.2V Nickel Metal Hydride with a final discharge voltage of 0.8V. The requirement on the high end is from multiple cell LiIon batteries with up to four cells in series each having a nominal voltage of 3.7V. Transient switching, adaptor interface regulation, and fault protection may drive the required system input levels even higher. With the addition of display technology the voltage rating of devices reaches upward to 35V. Typically mobile power IC current ratings can be as low as 50 mA for single cell NiMH applications and upward to 5-7A on the 3-4 cell LiIon applications. Even though the actual power level appears to be low, it requires all of the same safe operating limits and attention to power but on low voltage scale. Mobile power is one of the most diverse application areas for power semiconductor ICs. When you think about mobile devices, they are simple in operation and small in appearance but contain a very complex and functional system internally. Examples of such products are notebook PCs, PDAs, cell phones, pagers, MP3 players, minidisk, CD, DVD, GPS, portable signal transmission and reception (fish finder), robots, games, and a host of others, Generally, mobile product systems may consist of: processors and/or DSPs; a user interface - keys, display, and audio; communication and hardware interface compatible capability; wireless capability; battery management; charging and selection from external power sources; and standard switching, regulation, control, and conversion of power. The range of power applications for these mobile products includes: battery management such as various sophistication of capacity gauging for battery functionality in and outside of battery packs, battery or charger selection and interface, battery protection, and multiple battery operation. There is also power distribution involving large scale highly integrated SOC chips, a good example is cell phone power management; system power on board which includes integrated or singular functions- such as, smart power, conversion, controllers, and switches. Another area is display bias and lighting, and audio, and RF power for wireless signal transmission, and indirectly specific application power such as PCMCIA, USB, storage products, and other macro systems with power needs within the mobile systems. The trends in mobile systems are to increase functionality for the user, increase battery life/power efficiency, increase interface quality and compatibility, and decrease weight and size of the system. For example, when thinking about a PDA, ideally if it was as thin as the display, and the size of the display, then the smallest form-factor would be obtained. For hand held portable, thin is in. This drives the trend to integrate chip scale functionality at a higher level. This in turn drives a shrinking and diverse process technology lithography roadmap needing many special functions, a thinner and smaller form-factor package roadmap with efficient power handling capability, and of course, all of this complexity at a low-cost. This implies that the range and span of technology to harness these applications is very broad. Indeed optimization tradeoffs to yield competitive power device performance combined with the need for SOC level integration, precision analog functionality, robust ESD, and efficient memory, presents a very complex and challenging technology roadmap.
