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Smartphones: The New Power Management Summit

If I am to take press reports to be accurate, Samsung's newest smartphone, the Galaxy S4, is a marvel to behold. Looking past the high-profile features that have already gotten a lot of press, sensors seem to have attained higher status with the addition of an infrared device to sense when a finger is hovering over the screen. Even more interesting to me, however, is a new and somewhat untested sensor application: eye tracking using the camera's CCD.

It seems to me that eye-tracking could increase the duty cycle of the CMOS sensor quite a bit and, with it, power consumption. There are other power consuming features such as the 5-inch, 1,920-by-1,080-pixel (1080p) AMOLED screen. So it's little wonder the S4 packs a 2,600mAh battery — 500mAh (25 percent) greater capacity than the S3's.

I'm taking the “run-all-day” with recharge claim with a grain of salt. (I know. It depends on the application.)

This brings me to the real topic of this blog: power management. Designers of mixed signal power management chips must have nerves of steel to meet the constantly evolving specs and features of smartphones that have six-month product cycles. System architects seem to have little compassion for chip designers and the marketing guys, of course… Well, they have active imaginations. (One of the interesting trends in smartphone reviews recently is the increasing incidence of a reviewer saying that a feature is interesting, but unlikely to be used.)

While we users seek the thrill of scaling the new-feature summit and doing a victory dance, it means some analog designer has had to dance the how-low-can-you-go limbo to get us there.

How many smartphone users know (or care) that about half the board area of conventional smartphones is occupied by power, analog, mixed-signal, and passive components. This is a statistic that we typically don't see in teardowns, which tend to focus on the obvious but relatively less important digital devices, such as the processor.

Integration is the obvious answer, and there is plenty to integrate in a full-featured (dare we say “over-featured”) smartphone: battery management, display, LED indicators, sensors requiring miscellaneous ADC channels, and last — but certainly not least — processor and system power that require DC-DC converters with DVFS (dynamic voltage and frequency scaling) and low-noise, high-PSRR (power supply rejection ratio) LDOs.

A complete, highly-integrated SoC power management solution for smartphones would ideally have 2 ICs, 70-odd components, and take up about 120mm2 on the board. Compare this to a conventional solution with 9 ICs, 120-odd components and about 160mm2 of board space. Let me be among the first to publicly congratulate the power management IC designers that made the Galaxy S4 possible.

Earlier I noted that sensors seem to be getting a bit more respect from smartphone reviewers. I'm wondering when power management solutions — particularly SoC solutions — will get their day in the sun.

15 comments on “Smartphones: The New Power Management Summit

  1. Comfortable
    March 20, 2013

    “One of the interesting trends in smartphone reviews recently is the increasing incidence of a reviewer saying that a feature is interesting, but unlikely to be used.”

    I had to laugh at this.  Google and Apple each have about 1 Million apps in their stores.  The number of app downloads is about 10x the number of people on the planet ~ 50 Billion.  How can anyone possibly know what will and what won't be interesting to 1 Billion people?

  2. Brad Albing
    March 20, 2013

    I'm guilty of that – I see an app that looks cool and decide I need it. And then never use it.

  3. Jack Shandle
    March 20, 2013

    I personally don't think of apps as smartphone features. I think of features as more the hardware and software capabilities the phone has when you take it out of the box. One can compare apps as well but that — it seems to me — is another kettle of fish. 

    All that aside, stating opinions about products is what product reviewers do.

    Sometimes features are designed in just to see if they will be used. I've read that DoCoMo did not expect integrating a camera into a cell phone (it was the first camera phone, as I recall) was going to be as popular as it turned out to be.

    More to the point of my original blog, I'm still interested to know what strategy and technologies Samsung used for power management. How much mixed-signal integration was there?

  4. eafpres
    March 20, 2013

    @Brad–you should get an App that finds Apps that are interesting for you and automatically downloads them.

  5. eafpres
    March 20, 2013

    The evolution of mobile phones has been something to behold.  I recall when nobody thought they needed a camera in a phone, then attach rate for cameras went from 0 to 100% in nothing flat.  Nobody thought they needed a big touch screen but now nobody can live without one.  Sensors are the next thing we didn't know we needed.  Of course GPS (which is basically a complex position sensor) and accelerometers (those things that let your phone know which way you turned it, and if you shook it to “undo”) are already passe.  

    The more sensors, the more apps.  How about an app to detect gunshots, fights, car crashes, etc. and alert the authorities, providing a GPS coordinate location, your retina scan (which the phone stored without telling you) and the unique IP address of your IPv6 device.  If you carry a smart phone, in the future you won't be able to get away with anything!

  6. Brad Albing
    March 20, 2013

    Not sure which app to use to select the apps i need. Is there an app-finder to help find the app-selecter best for my applications?

  7. Brad Albing
    March 20, 2013

    I suppose – tho' probably not a problem if you're not doing anything for which the authorities may be concerned.

  8. Comfortable
    March 20, 2013

    @Jack 

    Smartphones have essentially one power chip that does almost everything; LED backlight, all the DVS switchers, maybe one-dozen LDOs, USB OTG power, audio, battery charger, touch screen, etc..  You'd be amazed at what goes into one of those parts.

    http://www.dialog-semiconductor.com/docs/site-pdf/dialog_pb_da9057.pdf?sfvrsn=2

    Dialog has been inside Samsung for a while.  Dialog does power for at least Apple iPhone, iPad and Samsung's Galaxy.  Probably others.

    These devices have become commodity parts.

  9. amrutah
    March 20, 2013

    @Jack,  I have to say that the PMIC system is getting complex day by day with the increased integration of features…Kudos to the team for pulling this off.  I haven't seen the S4 device but would surely like to play with the features you mentioned (“infrared device to sense when a finger is hovering over the screen”,”eye tracking using the camera's CCD”).

    The big power hungry beast is the Display and they better be controlled.  Another is there are so many switching devices/transistors sitting on the chip which needs a timing control.  The inrush current of the DC-DC can be a battery killer, a good control of this can be helpful to extend battery life…

  10. Jack Shandle
    March 20, 2013

    @Jack

    Thanks for bringing up to date. I had no idea how far behind the PMIC curve I had fallen.

  11. Brad Albing
    March 21, 2013

    Jack – some good points there on the intergration of analog functions – there are the problems you mention (and the difficulty of squeezing 10 pounds of cktry into a 5 pound ckt board. Then there are the ancilliary issues that arise – like thermal issues from power supply cktry being to near other analog cktry that's prone to drift.

  12. Netcrawl
    March 23, 2013

    @Jack nice article thank you for bringing us a great samsung news! bringing more information about what the latest inside Samsung S4. We still have no idea how Samsung S4 works, what's inside the “beast”. How do you compare Samsung new smartphones to other mobile players? in terms of processing power? speed?

  13. Jack Shandle
    March 26, 2013

    My blog that started this thread really had more to do with the impressive mixed-signal integration in the PMIC of the latest smartphones. I don't claim to be an expert in smartphone specs (or mixed signal integration for that matter) but if you want to compare specs here's a link http://www.macrumors.com/2013/03/18/samsung-galaxy-s-4-benchmarks-nearly-twice-as-fast-as-iphone-5/

    The Samsung Galaxy 4 S has certainly taken the lead but this sort of thing is definitely a leap frog situation.

  14. Brad Albing
    March 26, 2013

    BTW, that would be a meta-app.

  15. Brad Albing
    March 27, 2013

    So next week, Apple will have the better handset. Then after that, Blackberry will; and then (goto start).

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