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OUTLOOK 2018 – Digital power is playing a pivotal role as the IoT develops

Diwakar Vishakhadatta, VP and GM Analogue Products

The Internet of Things (IoT) is already pervading our lives and its power requirements are as broad as the number of applications. At one extreme are the edge devices connected to The Cloud, such as smartphones, Wi-Fi doorbell cameras and smart thermostats consuming just a few mW; at the other extreme in The Cloud are the server farms consuming MWs running sophisticated, fast algorithms that respond to your processing requests.

Those requirements span many orders of magnitude and the industry must develop solutions that span these extremes; it’s a huge task. At one end of the scale, those solutions might have to work with a coin cell battery, while the server farms require 48V buses to handle hundreds of Amps for powering advanced processors. The scale is mind boggling.

But there is a solution. Smart digital power processing brings the ability to deploy a differentiated approach. In this way, single phase and multiphase power delivery can be enabled, with one controller capable of handling six, seven or nine different switching elements, depending upon the load. These multiphase controllers can also determine how many power stages need to be active, maximising efficiency while delivering the power required to the system.

The scale of the challenge means different trade-offs are needed at each end of the IoT, but there is some fundamental ‘DNA’ which ties these devices together – communications.

Enabling the power controller to ‘talk’ to the system brings significant value as it can determine how much time has been spent at peak power, for example. That means each process could be designed based on how much power it consumes.

And communications also improves the ability to integrate devices such as microcontrollers, bringing more predictable and systematic control. For example, the system might need to run at high power for the next few cycles and the power stage can be programmed to be active at a higher level. When there’s lower power requirements, the smart power stage can gear down the system to improve efficiency.

Moving to multiphase power delivery will also bring benefits. A single output power stage has an area of peak efficiency, which means there is a big area where power is not being delivered efficiently. If you can combine multiple smart stages in parallel, each combination would have peak efficiency at different points, optimising the use of power.

Multiphase power capability has been available for server applications, but Intersil now also brings high-efficiency multiphase PMIC technology to low power products.

“Power devices will only become more intelligent because system designers see the benefit of their systems communicating. There are so many levels which can be addressed by smart power and this will be increasingly valuable.”

Diwakar Vishakhadatta

While power delivery is one part of the problem, power consumption is another. When it comes to IoT edge devices, the major factors are leakage and battery life; designers are now looking for PMIC devices whose quiescent power consumption is of the order of nA. That’s bringing an opportunity for energy harvesting to play a role.

Think about IoT devices in the home being powered by energy harvested when the doorbell rings or from ambient light. This could help such devices to become autonomous and remove the need for batteries to be replaced so often.

At the other end of the spectrum, servers have generally featured multiple power buses, with 48V being taken down to 12V and the 12V supply stepped down to 1.2V, for example. While there are benefits to intermediate stages, there are cost and efficiency downsides.

One area in which Intersil sees value is direct conversion from 48V to the required load. If you can do this while maintaining the same efficiency, there will be better control. While the adoption of digital and multiphase power represents a step change, widespread direct conversion from 48V will be another.

This spectrum of applications requires different solutions, but the concepts can be shared across them. For example, the control loop and architecture can be shared when scaling the stages and power delivery aspects.

Imagine a fast responding algorithm running on a digital loop at the heart of the system. At the mW level, this can focus on reducing quiescent current consumption and low leakage. At the MW level, the same ‘brains’ can be scaled to deliver hundreds of Amps through an external smart power stage.

Programmable power is becoming increasingly important. Computer ‘brains’ can communicate to a programmable ‘smart’ power stage, telling it what voltage and current is needed. It’s a symbiotic relationship; a dialogue between computing horsepower and power stage horsepower to allow the core to do what it needs to do and to then ramp down.

Turning to CMOS
While the power market in general has been slow to adopt CMOS technology, Intersil is creating a range of CMOS based solutions. Although there will always be the need for other technologies when it comes to power products, CMOS makes it easier to integrate MCUs and ‘digital smarts’.

Power product developers are also looking to increase the efficiency of their devices. Once you hit 90% efficiency, there’s only 10% to go, which makes the task harder. But the challenge for all power developers is not only to increase efficiency, but also to broaden the operating range.

A voltage regulator, for example, will have a particular efficiency curve, with a peak at some point, after which it will droop. But the regulator will not spend all its time at peak efficiency. So, instead of having an efficiency curve that changes shape, why not look to develop a device which has a flat line, allowing greater efficiency across the operating range? We’re looking for efficiency curves to be higher, flatter and wider.

If incremental change helps to reduce the size of a battery, it has tangible benefits to everyone in the supply chain.

Power devices will only become more intelligent because system designers see the benefit of their systems communicating. There are so many levels which can be addressed by smart power and this will be increasingly valuable.

Dynamic scaling is one example of how intelligence can be applied. Computing devices can scale their clock frequency so that when they are doing limited work, they run more slowly. Dynamic scaling can now be applied at the power delivery level. Because power scales as the square of voltage, you have to take advantage of low power levels. At full power, you need to be even more efficient. Digital and multiphase power will be significant factors.

But the challenge is to make sure this can be done cost effectively. CMOS is one way in which more capable solutions can be developed at improved cost points.

The merger between Intersil and Renesas represents an important step towards this goal. Renesas has SoC and MCU technology which is applicable in such markets as automotive, the cloud and networking. Every one of those processors will need power delivered and the ability to take advantage of smart communications. There is strong synergy between the two organisations that will enable optimised solutions from mW to MW. Renesas is bringing compute, Intersil is enabling the power.

In the future, system requirements will change in ways that we can’t predict today. Aspects such as wireless charging, power reception and transmission will become second nature and the user will have to do nothing at all

The focus on power efficiency will only become sharper as the world tries to become greener; in the future, every bit of power will matter.

INTERSIL, A RENESAS COMPANY

Intersil, a Renesas company, provides industry leading products in power management and precision analogue technology for the computing, consumer, industrial and hi-rel markets.

Author
Diwakar Vishakhadatta

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