Main issues and latest progress of PMP power management technology

All electrical and electronic devices require some form of power management , from simple switches to advanced power management units. Advances in power management are evident, and it has become a practical technology that will provide exciting innovations in the performance and functionality of tomorrow's devices. Effective power management enables new technologies and personalizes the end device, and legislation and standards have made power issues a key topic in the concept stage of product development.

The portable multimedia player (PMP) market is one of the fastest growing mobile entertainment markets. According to a 2005 IDC report, the sales of the PMP market will reach 2.4 billion US dollars by 2009. OEM manufacturers are ambitiously competing for a share of this market by launching some innovative PMP products with rich multimedia functions, and the market situation is exciting.

New Advances in Power Management

Every PMP has power issues, so power endurance and replaceability are important for its future development. Although power system performance is usually not the primary factor for consumers to choose portable products, the performance of the power supply is enough to affect the quality of the entire system. Currently, system designers widely use some design techniques to reduce system power consumption, such as: reducing operating voltage , optimizing system and CPU clock frequency, avoiding large current pulses during power-on ; effectively managing system batteries and system operating modes; minimizing bus activity, bus capacitance and conversion noise, etc.

We believe that PMP mainly faces the following aspects when dealing with power management issues: improving device conversion efficiency and reducing power consumption ; making device packages smaller; improving the integration of power management chips and systems to reduce overall system power consumption; meeting environmental protection requirements and having extremely high energy efficiency. Below we will interpret the current new power management methods for portable electronic products from four levels: advanced semiconductor processes and packaging technology, system consideration of power demand, management of load power consumption, and digital management and control.

Power management IC suppliers currently mainly use advanced semiconductor processes to improve conversion efficiency. For example, National Semiconductor uses low-voltage and low-power C MOS processes to reduce static current and improve conversion efficiency. In terms of reducing device size, the main focus is to further improve integration and adopt more advanced packaging technologies, such as CSP, LLP and Micro SMD, etc. Today, the development of packaging technology focuses on three aspects: the package is getting smaller and smaller, and the package chip is basically close to the size of the bare chip; the thickness of the package is constantly decreasing; and the I/O density is constantly increasing.

Another trend in portable product power management technology is the development towards power management and system integration. For a long time, processor suppliers and power management chip manufacturers have developed their own technologies, but the improvement of traditional technologies has always had its limitations. The efficiency of battery energy utilization has almost reached its limit, and the improvement in the future will not be large. To seek new breakthroughs in efficiency, it is necessary to change the traditional thinking and adopt a new method to comprehensively consider the power requirements of the entire system and use intelligent power management chips to manage the performance and power consumption of the system.

People usually think that power management is to feed power supply to the relevant load in the most efficient and cost-effective way. In fact, the development of power management technology in the future will gradually shift to managing load power consumption. That is, the characteristics of the load are divided, and the electronic system is regarded as a signal path, in which the circuits (whether discrete or built-in) are responsible for different tasks, such as signal amplification, conversion and processing. In this process, different circuits have different power supply requirements. For example, although some circuits perform different tasks, the power consumption is the same; while in other circuits, the power consumption of different tasks is different. These different requirements provide semiconductor products with an excellent opportunity to give full play to their strengths, and power management chips have become one of the most important components of electronic products. Therefore, the use of "dynamic power supply" technology, that is, adjusting the power supply according to the changes in the system load, can minimize the power consumption in different states. The realization of "dynamic power supply" requires the cooperation of the processor and the power management device.

Digital management and control is a new way of thinking for power management. As there are several complex loads in the distributed power structure and they are increasing in high-end consumer products, the demand for advanced power management technology is growing. Complex loads such as DSP, FPGA and microcontrollers often have more than one power channel. Driven by Moore's Law, the central core or DSP has been chasing lower voltages. I/O circuits or communication interfaces require standard higher voltage channels to operate. When the core voltage drops below 1V, the leakage current of the device increases. In order to reduce leakage current, advanced graphics and DSP generally use a bottom bias circuit that adds a negative voltage bias. Once the system's power channels reach more than 6, attention must be paid to the timing and control issues required for these channels to operate reliably.

Digital power control, also known as the "processor in the loop," is a completely different problem. Rather than using the traditional analog PWM comparator approach, it must compare two digital strings to generate pulse widths to drive the power switch. This adaptable technology can be used in applications where the load is constant for a period of time, allowing the power supply to run below 100kHz, such as power factor correction, uninterruptible power supplies, multiple chemical battery charging, and motor control; it can also be used in other applications such as PMUs for cell phones and PDAs that use several configurable PWM cores and control, diagnostic, and interface circuits. Subcircuits or peripherals in the run-time control circuit can provide the most appropriate operating voltage for their current state to save energy, and digital power control can make the regulator more sensitive and flexible.

Digitally controlled power management examples

At present, the more common functions of PMP include: MPEG4 playback, TV program recording, MP3/WMA audio playback, recording, picture display, games and storage functions (HDD/CF/SD), etc. Power supply is the root of the stability of the entire system, and power consumption is a sensitive issue for PMP, so this should be considered when selecting chips. In the past few years, power management device suppliers have been developing single-chip solutions that can meet multiple needs. This not only reduces the number of ICs, but also eliminates the discrete devices that support these ICs, reduces product costs, and reduces product size.

The LP5550 chip, the industry's first digitally controlled PowerWise power management unit (EMU) chip launched by National Semiconductor, not only supports adaptive voltage regulation to help extend battery life, but also supports more new features. Battery-powered portable products can reduce the power consumption of digital processors by using this highly integrated power management chip. The chip can be used with National Semiconductor's advanced power controller and ARM's intelligent power management (IEM) technology to reduce the power consumption of digital processor cores by 70%. Its advanced power controller can also support the open PowerWise Interface (PWI) standard established by the two companies for the industry.

In addition to considering power consumption in hardware design, it is also necessary to consider it in software design. After the hardware design is completed, the power consumption is generally determined, but the programmability of the chip can be used to reduce the system power consumption as much as possible. While providing the best effect, the software adjustment can be used to obtain the longest standby and playback time. One method is to put the chip into low power mode when in standby mode.