Power management challenges in portability

Spiraling energy costs and increased awareness of environmental issues such as global warming have opened up a whole new area of opportunities for energy efficiency in the semiconductor industry. Battery life in most electronic devices available today barely meets performance demands. The need for power management ICs has increased as consumers are embracing a more mobile feature rich lifestyle. Chips that can efficiently control the automobile systems to reduce emissions and get better mileage to several other consumer products that can help us reduce daily power consumption are in demand.

Portable consumer electronic device manufacturers are continuously challenged to develop cost-efficient, high performance, feature-rich solutions with longer battery life. Manufacturers are also forced to reduce development time to be the first to introduce new products in the market. With the development of ultra low-power codecs with embedded mini-DSPs and powerful graphical programming tools, manufacturers can meet complex requirements. Many of these new generation ultra low-power codecs can operate the analog and digital cores from a single 1.5V to 1.8V supply in low-power operation. For instance, in audio applications, it is possible to reduce power by operating the digital cores at voltages as low as 1.26V and down to 0.6 to 0.7V in Ultra portable notebooks.

Although many devices have low-power operating modes, additional power-tuning options enable designers to customize their power based on the individual configuration and processing options. This allows designers to minimize power tuning to be dynamically optimized based on the number of input and output channels, output drive requirements, sample rate, desired SNR performance for the input and output, and processing features used. Power tuning can make a significant difference in the battery life of a portable audio video device. The combination of ultra low-power data conversion and low-power signal processing in one chip enables significant power saving opportunities in conventional systems architectures that include an applications processor and codec. In these architectures, the ultra low-power codec can perform some or all of the audio processing functions of the applications processor. One of the powerful tools for longer battery life can be the new ultra low-power codec with embedded mini-DSP. These devices and their powerful graphical programming tools provide low-power audio solutions for a variety of portable audio processing and communication system architectures.

Very soon we will have netbooks and notebooks that will go all day without the need for charging. There are basically three challenges in portable power design: understanding overall system power budget; designing efficient power converters and controllers so the losses are minimized; and interactively managing the power requirements of the system.

The portable consumer electronics marketplace is very competitive and fast-paced. Quick time-to-market and very low power consumption empower manufacturers to reduce their design cycle while creating differentiated products. New generations of portable consumer devices such as wireless handsets, smart phones, PDAs and media players boast more features, higher performance levels and often smaller solution sizes. With their latest features, these devices all demand significant power. Some examples include cameras with resolutions of 3Mpixels or more, high-power photoflash LEDs or Xenon tubes, advanced audio and speaker functions, GPS and phones with portable high-resolution LCD-TV displays. Static and dynamic power requirements challenge designers. As portable devices become more feature rich, power requirements add up quickly. As a result, battery life gets shorter.

As ICs become more integrated as functionality increases, additional power rails are needed or higher supply currents are required for the same power rails. Most portable consumer applications use standard high performance Li-ion batteries, typically in a one-cell configuration. Given this limited amount of energy, manufacturers have to decide if customers prefer feature-rich applications with shorter battery lives or limiting the number of features and power requirements of their applications. Today’s customers want high-end devices without shorter battery lifetimes. Solving the portable power dilemma, many techniques are deployed. To address processor needs, IC manufacturers are taking the lead to decrease power consumption for given performance levels. To solve power requirements and power-saving challenges, new process technologies need to be developed. One example is a methodology called SmartReflex, used for DSP and TI’s OMAP processors. It reduces overall power consumption, optimizes system performance and increases battery life. With a broad range of intelligent and adaptive hardware and software techniques, it dynamically controls voltage, frequency and power based on device activity, operation modes and temperatures. Power-management designs provide the necessary voltage rails, and adjust voltage and currents based on processor needs. If the application is switched off or in a pre-defined power “save” mode, all processors and power-management devices usually have a light load or standby mode. Then, the current voltage levels decrease, and current consumption goes down to a minimum. IC itself will burn as few microamperes as possible in different operating states. Once the portable devices design is done, very little is left to influence voltage rail levels.

Serial interfaces in integrated power-management devices bring new levels of influence. Moreover, software controlled power management and monitoring can be realized, and multiple power-save modes can be implemented between existing full-load and system standby modes. Dynamic voltage scaling (DVS) using I2C interface has two different speed options: standard 100kbps and fast 400kbps. Implemented in discrete low-power DC/DC converters or power management units, designers can dynamically and precisely influence output voltages of the power-management devices and adjust core supply voltages for any processor unit. This design enables the system to meet exact performance requirements without sacrificing overall performance. Thus, minimum power is used for each operating condition of processor mode, extending battery life, reducing per device heat dissipation and enhancing overall system performance. The programmable DC/DC converter helps extend battery life in 3G smart phones, PDAs, digital still cameras and other portable applications. Another technique to reduce power consumption with the help of I2C interface is with more complex devices such as TI’s TPS65020. This is a highly integrated PMU with six output channels, three low-power DC/ DC converters with up to 97 percent efficiency and three LDOs. Different building blocks, like all three LDOs or DC/DC converters of this IC, can be switched on/off with the help of I2C to reduce power consumption and heat dissipation of the complete PMU.

Shutting down different blocks also decreases quiescent current consumption. In addition to the power saving schemes discussed, new manufacturing technologies will play a key role in the future. Communications will increase between DSP cores and their discrete analog power components to allow flexible on-time power adjustments and software controlled power schemes. All these improvements and methods must play together well to optimize performance and maximize battery life for the customer’s benefit.

Business opportunities are coming to India at a faster pace than one could have imagined until a few years ago. It is innovating and creating Intellectual Property (IP) that is in turn resulting in products and is aptly called “the sunrise industry”. Earlier, a high-definition TV with a DVD/CD/MP3/MPEG4 player and a good sound system was perceived to be the ideal home entertainment centre. Today, these features are expected in portable devices to keep up to the “on the move” lifestyle of the new generation. Going forward, consumers will demand high-quality mobile video/audio entertainment in smaller, slimmer, portable devices that require more functionality and higher-density memory storage, thus driving semiconductor manufacturers to consider new designs and manufacturing solutions. We must change not just what we do but how we do things as well. It is only by clearly understanding the state we are in and how we got here that we can begin to formulate a secure path toward the future. It is important to realize that there will be no silver bullet to solve the problem of increased power demands. Instead, effort should focus on tools that help the systems designers understand the performance and power implications. It time now to offer a system level solution rather than a component level solution and, TI is uniquely positioned to address this market need.


Author Information
Ramprasad Ananthaswamy is the Director for Power Management Products at Texas Instruments India.