New article: Power Delivery in a Modern Processor

Article: Power Delivery in a Modern Processor
By: Ricardo B (ricardo.b.delete@this.xxxxx.xx), May 15, 2020 10:31 pm
Room: Moderated Discussions
Rob Thorpe (rt.delete@this.nowhere.com) on May 15, 2020 6:36 pm wrote:
> Travis Downs (travis.downs.delete@this.gmail.com) on May 13, 2020 3:07 pm wrote:
> > Danjel McGougan (danjel.delete@this.mcgougan.se) on May 13, 2020 6:52 am wrote:
> > > David Kanter (dkanter.delete@this.realworldtech.com) on May 11, 2020 7:37 am wrote:
> > > > Friends, posters, and lurkers,
> > > >
> > > > Power delivery is one of the most significant challenges in modern processors. The power
> > > > delivery network (PDN) must meet the demanding requirements of modern CMOS technology,
> > > > supply power with excellent efficiency, and swiftly respond to changes in power draw.
> > > >
> > > > I just published a new post that goes into detail on power
> > > > delivery: https://www.realworldtech.com/power-delivery/
> > > >
> > > > It includes a brief discussion of system level power delivery, Intel's FIVR, and decoupling capacitors.
> > > >
> > > > As always, please take a look and comments/feedback/questions welcome here!
> > > >
> > > > David
> > > >
> > >
> > > Thank you for a great article!
> > >
> > > Just a minor nitpick:
> > >
> > > You mention lithium-ion batteries in laptops on page 2 and say that they output 3.7V DC.
> > > While it is true that an individual cell nominally outputs 3.7V, the battery pack of a
> > > typical laptop have multiple cells in series delivering a higher voltage. Typically there
> > > are 3 or 4 cells in series delivering ~11V or ~15V nominally from the battery pack.
> > >
> >
> > Yup, and I guess that's why power bricks for laptops usually output 15V - 20V: so they can
> > use the same step-down DC-DC converter for both wall and battery input. The similar voltage
> > range means that you could efficiently use a single converter optimized for that range.
> >
> > Or maybe 15-20V is just a convenient voltage on the safety vs power-loss tradeoff curve.
>
> The other reason is charging the battery pack itself.
>
> The cable from the charger to the laptop is quite long. You don't really want to run ~3.7V though it at
> lots-and-lots of amps. It would be very inefficient. So, that link has to be a fairly high voltage.
>
> Once you've done that you really want the battery pack at around the same voltage, at
> least just below. That way it can be charged from the cable. If the battery pack used
> a much lower voltage then you'd need *another* DC-DC converter for that. That's because
> everyone expects to be able to use their laptop while the battery is charging.

You always need a dedicated DC/DC to charge the battery because you don't want to charge the battery with a constant voltage from the wall-adapter.
But as Travis pointed out everything is simpler if the voltage from the wall-adapter is just a bit higher than the battery's maximum voltage.
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TopicPosted ByDate
New article: Power Delivery in a Modern ProcessorDavid Kanter2020/05/11 07:37 AM
  New article: Power Delivery in a Modern ProcessorMaynard Handley2020/05/11 10:03 AM
    Buried power rails, super vias, etc.David Kanter2020/05/11 11:44 AM
      Buried power rails, super vias, etc.Maynard Handley2020/05/11 06:06 PM
  InductorsMoritz2020/05/11 12:01 PM
    InductorsDavid Kanter2020/05/11 12:36 PM
  New article: Power Delivery in a Modern ProcessorTravis Downs2020/05/12 07:53 AM
    New article: Power Delivery in a Modern ProcessorJason Creighton2020/05/12 09:15 AM
      New article: Power Delivery in a Modern ProcessorDan Fay2020/05/12 09:35 AM
        New article: Power Delivery in a Modern ProcessorJason Creighton2020/05/13 09:09 AM
          New article: Power Delivery in a Modern ProcessorRicardo B2020/05/13 11:47 PM
            New article: Power Delivery in a Modern ProcessorMichael S2020/05/14 12:29 PM
              New article: Power Delivery in a Modern Processoranon³2020/05/14 05:22 PM
              New article: Power Delivery in a Modern ProcessorRicardo B2020/05/15 05:06 AM
                New article: Power Delivery in a Modern ProcessorMichael S2020/05/15 05:13 AM
      New article: Power Delivery in a Modern ProcessorTravis Downs2020/05/13 03:01 PM
    LDO power savingDavid Kanter2020/05/12 10:16 AM
      LDO power savingYoav2020/05/13 03:56 AM
        LDO power savingTravis Downs2020/05/13 06:44 AM
          LDO power savingDan Fay2020/05/13 07:03 AM
            LDO power savingTravis Downs2020/05/13 03:02 PM
              LDO power savingRicardo B2020/05/14 12:08 AM
    Asynchronous CPU?dmcq2020/05/12 01:05 PM
      Hindered by device testing and design validationPaul A. Clayton2020/05/12 02:13 PM
        Hindered by device testing and design validationMark Roulo2020/05/13 08:22 AM
          Hindered by device testing and design validationAnon32020/05/14 07:06 AM
  Work scheduling for moderating powerPaul A. Clayton2020/05/12 10:15 AM
    Work scheduling for moderating powerDavid Kanter2020/05/12 10:40 AM
      Work scheduling for moderating powerPaul A. Clayton2020/05/14 09:27 AM
    Work scheduling for moderating powerTravis Downs2020/05/12 01:25 PM
      That is certain one real world example (NT)Paul A. Clayton2020/05/14 09:28 AM
  New article: Power Delivery in a Modern ProcessorDanjel McGougan2020/05/13 06:52 AM
    New article: Power Delivery in a Modern ProcessorTravis Downs2020/05/13 03:07 PM
      New article: Power Delivery in a Modern ProcessorRob Thorpe2020/05/15 06:36 PM
        New article: Power Delivery in a Modern ProcessorRicardo B2020/05/15 10:31 PM
  Bypassing capacitors & testingRob Thorpe2020/05/15 06:54 PM
  New article: Power Delivery in a Modern ProcessorRicardo B2020/05/15 10:22 PM
    New article: Power Delivery in a Modern ProcessorDavid Kanter2020/05/16 09:03 AM
  New article: Power Delivery in a Modern ProcessorPaul2020/05/31 11:08 PM
    New article: Power Delivery in a Modern ProcessorDavid Kanter2020/06/01 07:52 AM
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