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How is power being supplied through the launchpad from either IDCI or OTG USB port?

Thomas Phan
Intellectual 785 points

I'm not sure if this forum accepts PCB/schematic design question, but I will move my question over to another forum if needed.

I'm trying to learn how to do PCB design, and I thought that it would be best to take a look at the schematic and board files for the current launchpad that I'm working with. When I'm trying to see how power is being supplied to the MCU, I'm having a hard time tracing back from where power is entering (either through IDCI or OTG USB port) to where power should be going to (the VDD pins on the MCU). They seem to be leading to this part U4, which is a power-distribution switch, but then it goes off to some other places from there, and not to any of the VDD pins on the MCU. There is a pin from the switch that leads to all of the booster packs' and GPIO breakout holes, but that's to supply power to other peripherals, so not really what I'm looking for. 

The next two pictures show the VDD lines for the MCU, as well as a jumper that is named "MCU 3.3V". It lights up together with the VDD lines when I select VDD, but I don't see anything leading to or from it. What is it there for?

Thanks

  • 0
    Guru 47900 points

    Thomas Phan said:
    ... forum accepts PCB/schematic design question(S)?

    Not really - finding a (much) more appropriate reference source for such NON-MCU questions is preferred.

    In addition - you've chosen one of the more complex pcbs to examine & question - have you not?   Would not a far simpler pcb make more sense?   Surely many of your current questions would "self-resolve" if that (simpler) approach was followed.

    One final point - pcb design/layout is (both) a science & an art.   We note (many) here "bound/determined" to create their own pcb.  Most "pro" pcb firms have personnel w/many, many years "in the trenches."   Is it realistic to expect that (years) of experience, learning & focused effort can be bypassed?  Might it prove "important" to know what "should" or "should not" be attempted by neophytes?

    So too there is GREAT desire (always unjustified) for new users to create their "own projects."   In both cases (pcb design & own project) - almost always - failure (at minimum, sub-optimal performance) results.   Your focus upon the MCU - its "care, handling, & application" is likely to produce the fastest & most efficient means to your tech growth.

  • 0
    TI__Mastermind 22580 points
    Hello Thomas,

    We don't review schematics/layouts unless there is an issue. There is enough documentation in the form of reference designs and design guides along with system design guidelines on ti.com.

    I second cb1's recommendations. If this effort is for learning, it is best to start off by doing simpler designs where the PCB design is a lot more easier to debug if there are errors. A PCB design of an MCU has lots of nuances, especially one involving devices like TM4C, and is not the ideal route for learning.

    Thanks,
    Sai