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To reduce power consumption in portable applications

Print View , by: iSee ,Total views: 17 ,Word Count: 1762 ,Date: Wed, 26 Aug 2009 Time: 4:03 AM

Wireless hand-held devices, smart phones, PDA, and a new generation of portable media players and other consumer electronics products with more features and higher performance, usually the size has become smaller. As these latest features, these devices require high power consumption.

Related examples are endless, with more than 3 million pixel resolution, high-power flash LED or xenon flash tube camera, advanced audio or speaker functions, as well as high-resolution LCD-TV with a portable wireless phone display. Static and dynamic power requirements to the designers presented a serious challenge, it is essential to effectively manage them. With the increasingly feature-rich portable products, the application quickly to the single power supply also raised a higher demand, resulting in a corresponding shorter battery life.

In addition, the analog and digital baseband IC processor unit, the host CPU and the graphics and audio processors, both in nature and in the integration progress in many fields has been increasing. With the increase of product features, IC integration also will be upgrading, so the need for more power rail, or in the same amount of power rail is applied to a higher supply current.

Most of portable consumer products using the standard high-performance lithium-ion battery (usually a single cell configuration). In view of the limited battery power, manufacturers have to make a case for the following two kinds of decision: either to the expense of shorter battery life to provide users with feature-rich applications, or the expense of application of feature-rich, rather to ensure long battery life. But today's consumers want both high-end products, while demand has long battery life.

The power consumption of portable devices to solve problems

In order to solve these design challenges, many technologies have come out. In order to meet the needs of processors, IC manufacturers take the lead in reducing the power consumption of a given level of performance. DSP, or OMAP core standard digital IC manufacturing using 90nm process technology.

Since late 2005, most next-generation 65nm process had been put into mass production. Through "compression", usually double the transistor density. Such technologies would be the same design compressed to half its original size, and the performance of transistors than the original has increased by approximately 40%. This technique greatly reduces the core power supply voltage requirements, while the current request the same or higher. On the other hand, were significantly higher leakage power will be further degrade performance.

Other ways to reduce power consumption (modulus of non-IC manufacturing technology), including a variety of low-power modes, clock gating, dynamic voltage and frequency scaling. These technologies in the design plays a very important role. In order to meet the power consumption and lower power requirements, the need to develop a new type of manufacturing and process technology. Is applied to a dsp and OMAP processors called SmartReflex new method is a good example.

In the silicon-IP level, the static leakage power consumption is significantly reduced 1000-fold. Cell library in a power management device to achieve regional power domain particle methods (granular approach), while the different building blocks of integrated circuits and systems of power and performance of the coordination.

This method not only reduces the overall power consumption, optimize system performance, but also to extend battery life. With a wide range of intelligent and adaptive hardware and software technologies, SmartReflex technology can be based on device activity, modes, and temperature changes, voltage, frequency and power consumption for dynamic control.

SmartReflex techniques include dynamic and adaptive voltage scaling, dynamic power switching and standby leakage power management. Dynamic voltage scaling is likely to involve an external power management devices and software.

For example, according to the requirements of the load on the processor, core power supply voltage can be adjusted to meet the needs of all of the performance to run or in the standby mode, power saving mode. Discrete low dropout (LDO), the low-power DC / DC converters, multi-channel Power Management Unit (PMU) or other power supplies available to serve the circuit board and processor power (depending on system requirements).

Power management design provides the necessary context for all processors, voltage rails, as well as the correct voltage and current. If the application is closed, or switch to a predefined power-saving mode, then all processors and power management devices are usually entered a light load or standby mode.

Therefore, the current voltage level will be further reduced, while current consumption is also reduced to the minimum. In an ideal situation, each IC consumes only a few μA of current. So far, the above are static mode. Once the power management design, then it is almost impossible to change the voltage rail level.

Recently, the separation of low-power step-down DC / DC converters and highly integrated multi-channel power management unit can already use I2C serial bus. With the serial interface in the discrete power management devices to be used, to the power supply voltage provides a new means of influence.

By software tools and processor control functions and a standard I2C serial interface, combined digital and analog power management chips of information between the higher levels of performance can be exchanged.

Voltage, current and power budget, real-time regulation has become a reality; In addition, you can achieve the power management and monitoring software control, thus the existing full-load and the system in standby mode can be achieved between the various power-saving mode.

Dynamic voltage scaling. I2C interface has two different speed options: the standard 100 Kbps and faster 400Kbps. In the discrete low-power DC / DC converters or power management unit to implement dynamic voltage scaling, the designer can dynamically and accurately change the discrete power management devices, the output voltage, then adjust the unit any processor core supply voltage.

This design requires the use of fast-DC / DC converters. For example, 3 MHz or higher conversion frequency converter (see Figure 1) can be guaranteed fast signal transient response.

To reduce power consumption in portable applications

Figure 1: I2C can dynamically adjust and regulate the main DC / DC converter output voltage

In addition, low-power DC / DC converters or power management unit should have a different mode, for example, PFM or compulsory pulse frequency modulation, in order to allow them to adjust their own or through the I2C control signals into a system of power distribution.

The design without sacrificing overall performance in the case of precisely meet the system performance requirements. Therefore, each processor in a working state or Patterns to achieve the lowest power mode, thereby prolonging battery life, reduced heat dissipation for each device, and improve overall system performance.

Reduce power consumption. In this case, the separation of low-power DC / DC Converter TPS62350 uses SmartReflex technology. A miniature chip-scale packaging ball grid 12 of the single-channel step-down converter delivers up to 800mA of output current exceeds the efficiency of 95% of the single-cell Li-ion battery input voltage range. The use of I2C interface, the output voltage can be adjusted to support the processor and can be "micro-steps (tiny step)" to adjust voltage rails, the minimum to 0.6V.

This programmable DC / DC converters help to extend the 3G smart phone, PDA, digital cameras and other portable applications, battery life.

With I2C Interface Another way to reduce power consumption, such as the TPS65020 is used such a device (see the next Figure 2). This is a highly integrated PMU, with six of its output channels, three low-power efficiency up to 97% of the DC / DC converters, as well as three LDO.

To reduce power consumption in portable applications

Figure 2: TPS62350 single-channel step-down converter delivers up to 800mA of output current, beyond the single lithium-ion battery input voltage range

In the device, I2C be able to dynamically adjust and adjust the processor core power supply is usually the primary DC / DC converter output voltage. The other two DC / DC converters can be used for I / O power supply, memory or other functions supply. The different building blocks (such as the IC for all three LDO or DC / DC converter) in the I2C interface, with the help can be closed / opened in order to reduce the overall power consumption and heat dissipation PMU. Close different modules can also lower the quiescent current consumption.

In addition to power-saving methods have been discussed in other, new manufacturing technology in the future will play an important role. With the development of process technology from 90nm to 65nm or even smaller, the technical implementation discussed here will become more important.

In the DSP core and its discrete analog power will increase the communication between components in order to achieve a flexible real-time software control of power conditioning and power consumption of the program. In short, all of these improvements and methods must be used in conjunction with well, to achieve optimal performance and maximize battery life, thereby benefiting consumers.

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