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RoadTest request: ICs that manage the power up sequence of a board

Jan Cumps

Many designs require that the power rails are enabled (and at shutdown disabled) in a certain sequence.

The controller voltage may have to be stablilised before the I/O voltage is activated, etc.

A lot of the development boards we use day-to-day have such a power management chip on-board. They are used for microcontrollers, FPGAs and many single board computers: Raspberry Pi uses one, the BeagleBone, several LaunchPads, Papilio FPGA boards...

 

Maybe, , you can ask IC suppliers if they are interested to run a RoadTest where such a solution can be validated?

It does not have to be an evaluation kit. The Road Test kit could be the raw IC, and the components you need to sense and switch rails?

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  • and , if you don't need the IC, you don't need it image. For many designs you can just turn on the power. For some, you use an RC circuit + fet to delay a secondary rail a little.

    There are controllers, FPGAs and other devices (I mentioned a few in the proposal) where power management is needed  by default, or desired when you want to have a deterministic state of I/O at startup - no matter what's happening at I/O pins you don't have control of)

    Think with me a little here image. It's a thing.

     

    Direct critique aimed straight towards both of you image : BB, Pi and LaunchPads all have a microcontroller on board. Still they have a power manager in the circuit. Why not the controller? Why not an LM3881?

    (edit: although the LM3881 is in scope for what I'm suggesting. Time based power rail sequencing is a valid option in many cases)

  • in reply to Jan Cumps

    Hi Jan,

     

    I too think its a worthwhile RoadTest, LM3881 was just the one I was using if you wanted some ideas about what people are using. Although power management encompasses many features, I only referred to power sequencing, whereas the boards you mention use parts with things like in-built reset, DC-DC converters, sensing, etc, in the single chip.

     

    It's definitely less integrated the approach I took (no technical advantage in my case, just easier to assemble because that was what was important to me), compared to the fully integrated solution on-board the BBB, Pi etc (I don't think they have a microcontroller on-board, I could be wrong, but I'm not suggesting one way has a technical advantage to the other - just that sometimes things are easier for non-technical reasons too).

     

    Some commercial designs seem to split the functionality in places too, e.g. I looked on an Intel based motherboard, and they used separate DC-DC converters, not integrated in a single IC. But their power requirements are very different from Pi, BBB of course, so in the motherboard case it was more technical reasons like heat dissipation and locating the converters close to where they individually needed to be.

  • in reply to shabaz

    The things that led me to this path were USB-C, where you have to negotiate the power delivered by the supply;

    and Rossmann's MacBook repair videos, where he explains how to troubleshoot power-on issues by following and probing the power-on sequence.

  • in reply to Jan Cumps

    Ah, I see. Also, I hope we can roadtest USB-C related tech sometime too.

    I'll have to check out his video, they are always fun to watch.

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