the future of power management - display plus

14/10/2013 Display Plus

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The future of power management in the mobilecomputing market

2013년 07월 30일 (화) 01:16:11 Display Plus [email protected]

A record year for smartphones and tablets

More smartphones are forecast to be shipped globally than feature phones for the first

time in our industry in 2013. IDC (International Data Corporation) predicts some 918.6

million smartphones will be shipped vendors, representing 50.1% of the total worldwide

mobile phone market. We’re seeing smartphone prices fall globally, a greater choice of

entry-level to high-end models on market and an acceleration of 4G LTE network roll-

outs, making these "do-it-all" devices an increasingly attractive option for consumers.

China supplanted the US last year as the global leader in smartphone shipments, but we

are also seeing burgeoning demand in Brazil and India with their large, populous

nations, high growth economies and rising middle classes.

The prospects for tablets are similarly good. Tablets are likely to out-ship notebooks in

the US for the first time this year. The buying public can't get enough of the devices

and this is expected to persist in the longer term on a global basis. IDC has recently

raised its tablet shipments forecast for the 2013–2016 period, suggesting global tablet

sales will reach 190.9 million in 2013. By the end of 2017, IDC expects tablet vendors to

have shipped in excess of 350 million units with a rapidly growing choice of smaller,

cheaper slates. We’re seeing a confluence of high-end tablets and ultra-mobile

notebooks as the world figures out how these devices can co-exist and hybridise.

Effective power management presents an increasingly complex array of design

challenges for these portable devices. Poor battery life contributes to customer

dissatisfaction with a new smartphone more than any other single feature. This will only

become more of an issue over time unless vendors take new innovative approaches to

their power management strategy.

4G smartphones use substantial battery life searching for next-generation network

signals, which are currently scarcer than 3G signals, and they eat up more battery

power decoding high levels of data that can be transmitted within the spectrum. In

addition consumers are now using their mobile devices more extensively – they talk,

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text, email and surf the web, but they also want to able to view higher definition videos

and GPS maps, have two-way video calls with their kids, play more immersive games

and stream music. At the same time consumers demand displays that are brighter,

bigger and incorporate better touch functionality and, in the future, haptic feedback.

Each of these features is a major battery drain, creating a need for effective power

management technologies.

Power management remains a critical challenge

In the past, power management technologies used to be integrated within the

application processor. However as the importance of optimising power performance

becomes more important and technically challenging, this on-chip approach is no longer

possible. Dialog’s companion Power Management Integrated Circuits (PMICs) are highly

programmable, enabling them to support the voltage scaling and power delivery

sequencing required by single or multi-core application processors, as well all the sub-

systems in the phone, such as the network and connectivity stack (3G, 4G LTE, Wi-Fi,

Bluetooth and NFC), the display, high megapixel cameras and more.

Figure 1: The functionality expected in modern mobile devices demands increasingly



complex power management capabilities.

There are good reasons for having a companion PMIC that is highly integrated with all

the key communications, multimedia and processing blocks on the board of a mobile

device. The PMIC has to generate up to 30 different power supplies to be able to feed

different parts of the applications and baseband processor with the right combination of

voltage and current. If you take an on-chip approach to power management, with the

application processor handling these tasks, you need a high-current supply that can

only be carried by aggregating many pins. SoC designers can avoid the additional die

and efficiency cost of on-chip power management by using individual low-voltage, low-

current supply rails that are supplied off-chip by the dedicated, companion PMIC.

With a long legacy of delivering different power management designs for world-leading

mobile phone manufacturers and portable consumer OEMs, Dialog specialises in

optimising all aspects of the design, including electrical, thermal and mechanical

packaging considerations to optimise power performance of these portable devices.

A diversity of power management needs

The market for smartphones is diversifying as they are adopted on a global basis. A

platform approach is becoming increasingly more important in smartphones as vendors

seek to give consumers more choice of models, spanning the high-end to entry-level

markets with optional 4G or NFC connectivity, depending on the market. They are under

pressure to launch new models every six to nine months in response to consumer

demand for “the latest and greatest features” and competitor activity and a platform

strategy helps them manage this process while containing costs.

We’re also seeing a new wave of smartphone handset vendors coming onto the market

working with System on a Chip (SoC) vendors who provide a complete reference

platform to OEMs to help reduce time-to-market and reduce development risks. Of

course, it’s important that OEMs have the capacity to customise a platform to

differentiate the products they are developing on the market.

Dialog’s highly configurable PMICs enable vendors to be flexible in designing their

smartphone platforms and launch multiple models and designs for different markets and

over the “life cycle” of that product. It supports late changes in board-level designs as

additional functionality that is added into smartphone platforms during the R&D

process. This can also help to reduce PMIC inventories and respond to the consumer

market’s need for volume flexibility. This customisability is also a huge advantage to new

handset vendors working with SoC vendors.



The move to multicore devices

The vast majority of smartphones today are single- and dual-core SoCs. At the very

high-end, there is a smattering of quad-cores. The same is mostly true of tablets,

although the larger power budget (up to 4W for a passively cooled device and as high

as 7-8W for systems with fans in comparison to around 1W for smartphones) means

that the processors tend to skew towards higher core counts.

Some have questioned the need for multi-core mobile computing devices. It’s certainly

true that the majority of PCs sold today have dual-core CPUs as most software

applications are single threaded rather than multi-threaded and able to work off a

number of cores. Software for mobile devices is even less amenable to threading.

Despite this, there is a significant power advantage to be had from multicore devices.

Multi-core devices delegate simple tasks to one core, while directing more complex,

power-hungry tasks to the other core. Each of the quad- or octal-core application

processors needs to be powered up and down into and out of sleep state in particular

sequences. The Power Management Integrated Circuit (PMIC) acts as a conductor for

the system, telling individual blocks inside each baseband or applications processor

device when to wake up and when to go to sleep to save energy. Most workloads will

still be single threaded and need high frequencies, so the SoC must be able to efficiently

deliver both aggregate throughput and single-core performance.

Heterogeneous cores, which ARM bills as “big.LITTLE", pair a small and efficient core with

a larger and more complex core and switches between the two. The challenge again is

power and reducing switching penalties through an effective power management

solution. Put simply, there isn’t enough power or cooling for every block to be in a high-

performance mode simultaneously. When running a highly immersive and interactive

game, the display and GPU will draw much of the power; the CPU will actually have to

reduce frequency and voltage to deliver the best overall performance. This becomes

even more complex if there is significant wireless traffic as well. As a result, an advanced

PMIC is required to handle these switching processes.



Figure 2: Power management is migrating from the application processor into a

dedicated external PMIC, like this DA9063 from Dialog Semiconductor

4G LTE and the power performance challenge

4G LTE smartphones also present a power performance challenge. Today’s digital

modulation techniques compress more data bits into every RF channel, resulting in more

complex waveforms with higher “crest factors,” expressed as peak to average power

ratio (PAPR).

LTE signals have a very high crest factor (typically, 7.5- to 8-dB PAPR), resulting in a

much higher peak power requirement for the transmitter. Traditional fixed supply PAs,

which are only energy efficient when they are in compression, at the peaks of the

transmitted waveform. If designers opt to use a larger power amplifier (PA) with an

increased supply voltage, a lot of energy is wasted and the time consumers are able to

use LTE device between battery charges can drop to a matter of hours. To optimise

power performance two companion PMICs are required to manage the more complex

voltage and current requirements of the smartphone.

Saving board space

OEMs are also under pressure to save board space, freeing up “real estate” for new

functionality and helping them keep their devices thin, and reducing costs. The use of

3D packing technology – or chip stacking – is paying dividends here. Typically, chip



stacking relies on connecting different layers of the stack with low-density bond wires or

solder bumps. Dialog is one of the first companies to combine a fully configurable PMIC

with a low power audio codec that is monolithically integrated, or stacked, in a single

package to deliver significant board space and cost savings to its customers. This can

involve the integration of over 30 different high- and low-voltage circuits and analog

functions on a single chip.

It’s not enough just to save space. At the same time Dialog’s audio codecs ICs deliver

superior audio performance for consumers’ peripherals. Dialog’s audio codecs filter out

extreme background noise and increase the fidelity of the sound through the integration

of advanced echo cancellation software within the DSP (Digital Signal Processor) that

delivers a rich, deep base and clear high frequencies even in noisy environments. This is

complemented by amplifier technology to improve audio quality through the headphones

and speakers.

Manufacturing trends

We’re also seeing the relentless drive towards thinner and smaller geometry devices

that pack in more features than ever before. Ever-finer feature sizes potentially

introduce the perils of high leakage current due to short-channel effects and varying

dopant levels, which ultimately threaten to derail the industry’s progress to smaller

geometries.

We’ve also seen the advent of novel stack materials, such as high-k/metal gates, and

now fully depleted transistors, for example, FinFETs. Modern FinFETs are 3D structures

that rise above the planar substrate, giving them more volume than a planar gate for

the same planar area. Given the excellent control of the conducting channel by the gate,

which “wraps” around the channel, very little current is allowed to leak through the body

when the device is in the off state. This allows the use of lower threshold voltages,

which results in optimal switching speeds and power.

There is plenty of other promising research for the roadmap. Dialog, for example, is

working with Taiwan Semiconductor Manufacturing Co (TSMC), the world’s largest

contract chipmaker, on state-of-the-art 0.13 micron bipolar-CMOS-DMOS (BCD)

technology to integrate advanced logic, analog and higher voltage components into a

smaller form factor, single-chip power management IC to support next generation

smartphones, tablets and Ultrabooks™.

The BCD process technology epitomises the relentless innovation that drives the

semiconductor industry – on the application, design and process technology fronts. The

technology incorporates incorporates analog Bipolar (B) components, Complementary



Metal Oxide Semiconductors (CMOS) and high-voltage transistors Double Diffused Metal

Oxide Semiconductors (DMOS) on the same die. System designers are embracing this

technology since it reduces power losses, board space and costs. Silicon partners like

Dialog are championing BCD as it is helping us build better, smaller and more innovative

products. While the foundries also have a key role to play as BCD technology is

manufactured on 200mm wafers, allowing them to extend the usefulness of their almost

fully depreciated lines and either reduce the cost for end-customers, preserve margins

or free up investment for other emerging technologies.

Making smart future bets

Dialog also continually has an eye on the future, trying to identify the emerging

technologies that will continue to transform our industry. For example, we have recently

partnered with Arctic Sand Technologies, Inc., an MIT spin-off is commercialising an

innovative new approach to power conversion for multiple markets, including

smartphones, tablets, Ultrabooks™ and data centres.

DC-to-DC power converters are the underlying building block of today’s power

management Integrated Circuits (ICs). Arctic Sand’s patented TIPS™ (Transformative

Integrated Power Solutions) technology uses a unique approach for conversion, based

on switch capacitive techniques.

The technology facilitates the use of smaller inductive components, resulting in

increased efficiency and an overall higher power density factor over and above today’s

competing technologies, delivering significant advantages in portable and data centre

applications.

Conclusion

Clearly, demand for mobile computing devices is only going to increase according to

industry forecasts. Mobiles are evolving from personal information devices to mobile

computing platforms that are critical to our everyday needs. Power performance is fast

emerging as the defining issue of our era. Smartphone owners who are highly satisfied

with their device's battery life are more likely to repurchase the same brand of

smartphone, compared with owners who are less satisfied.

Consumers want a greater variety of devices in our lives. For example, a minority of

consumers actually buy a 3G or 4G data plan with their tablets, preferring to use Wi-Fi

in their homes and business to access and consume media. What is clear, however, is

that people want to live in a untethered, wireless way. This places added pressures on

battery life of portable devices, requiring a relentless focus on power management

innovation across the triple play of smartphones, tablets and the new hybrid tablets-

come notebooks coming onto the market. It’s why Dialog is laser-focused on



continuous innovation with technologies that give mobile devices the power to be

portable, personal and connected.

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