The Importance of System-Level Power Management for Portable Products

It is well known that today's consumers want smarter, more compact and thinner electronic products, but designers of such devices continue to face the same demand for extending battery life. Ten years ago, some mobile phones could be used for a whole week on a single charge; today, battery technology faces the challenge of maintaining this record, with only a few products being able to use more than a day under normal use without recharging.

In recent years, the growth of battery capacity has only reached about 11% per year, and there is no sign of acceleration. However, the performance and functions provided by smartphones, tablets and notebooks are unimaginable ten years ago: such as full-color, high-resolution touch screens, multiple wireless transceivers and receivers, several GB-level memory, and near-field communication (NFC) and other functions, and these more functions also mean higher power consumption. However, as more and more functions are added, the growth rate of power consumption performance has shown a small increase in the same amount.

As consumer electronics devices become more complex, the idea of ​​having independent power management circuits for each circuit function is quickly becoming obsolete. Effective power management requires a system-level approach and a deep understanding of how the application processor and its peripherals interact. But how do different circuit functions communicate? When does the processor need to be intervened? Under what circumstances can it be kept in sleep mode? What is the significance of using different sleep modes?

Also, how fast can the processor wake up the circuit? Does the circuit's supply voltage have to be constant, or can it be varied to save power, and under what usage conditions should it be evaluated? What does an 'always on' connection mean for optimal power management? Only by understanding these topics can product designers expect to minimize system energy consumption. And, since battery life is a deciding factor when consumers make purchases, developing the best energy management system has become the key to success in the current consumer electronics market.

It is worth mentioning here that usually when we talk about "power management", it actually refers to the issue of "energy management". Energy consumption is the product of power consumption and time. Obviously, the time each circuit is powered on has a decisive impact on battery life, such as the switching of the function sequence and the speed of sequencing. In many cases, the peak current required by the processor may be up to 10 times higher than the average current. If the power management circuit has a higher ability to manage the peak and can maintain the minimum power demand time, the system can achieve more effective overall energy management.

Trying to manage all possible operating scenarios for a smartphone, tablet or other portable electronic product has become so complex that discrete analog power management with a standalone digital controller is no longer feasible. This approach is too expensive in terms of overall bill of materials cost, product assembly and board space consumption, and does not provide the performance or functionality that a dedicated power management IC (PMIC) can provide.

Consider this. In an 8x8mm BGA package that is only 1mm high, a PMIC manufacturer has included multiple multimode DC/DC converters, some of which can be paralleled to provide more than 14 amps of total current. It integrates multiple LDO regulators, multiple GPIO pins, PWM drivers for RGB LEDs, power and rail switches, system-level monitoring, and a watchdog timer.

Some advanced devices have switching frequencies of 6MHz or higher to minimize the size of the external inductor; in contrast, discrete circuits rarely have efficiency above 1MHz. Such power management ICs may have a wide input voltage and can operate from anything from a single lithium battery to a USB power source.

Perhaps most importantly for system designers, today's highly integrated components have intuitive software programs that enable testing and rapid optimization of power sequencing and control, providing opportunities for product differentiation. The same tools can be used to set dynamic voltage regulation so that analog circuits are only provided when the required performance level is required. This complexity of energy control was unimaginable a decade ago, but without it, many of today's consumers would be hindered by bulky batteries that affect the wonderful experience of using mobile devices.

Today’s mobile devices have seen significant improvements in time-to-market, size, cost, performance, reliability, and operating life as processor technology improves and energy consumption is reduced through an integrated, system-level approach. For true smartphones, a week-long battery life may no longer be a dream…because we are working to make it a reality.