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TM4C1294NCPDT: Crystals for TM4C1294NCPDT

Eduardo Barcellos
Intellectual 420 points
Part Number: TM4C1294NCPDT

Good afternoon, 

I'm looking for some 25MHz crystals that works well on the TM4C1294NCPDT MCU. Most of the ones recommended on page 1841 of the datasheet are either out of the market or out of stock on all suppliers. Only one I can find in stock.

The reason for "some" 25MHz crystals is because I'm designing a board and would like to make sure new crystals are available in case the one I'm using is out of stock or becomes obsolete. Redesigning the board because of that would be a problem.

Also, everytime I tried to pick a new crystal myself I had some kind of problem with the ethernet controller. So I'm concerned about that.

Thanks in advance!

  • 0
    TI__Guru*** 135355 points

    Hello Eduardo,

    Thanks for reaching out and I definitely understand the struggles right now with the current market environment. Our intent was to provide sufficient options to select from, but that isn't panning out well currently.

    Unfortunately I don't have any additional recommendations to make beyond that list - those crystals were all ones where we worked w/ crystal manufacturers to run simulations and verify functionality with our device leading up to the release. At this moment, we don't have the capability to make further evaluations and simulations on our end to add additional devices to the list.

    What other customers typically do is look at the specifications for the main oscillator listed on the datasheet and then reach out to their preferred crystal vendor(s) to get an oscillator within those specs. Crystal vendors can also help with guiding the correct connections and capacitance values etc. to use. I know of many customers who had success doing this, but the key is to work w/ the crystal vendors directly and not just select a device from online specs and put it down without any verification of how it should interface with the TM4C MCU. Hopefully that gives you a next step to pursue here.

    Best Regards,

    Ralph Jacobi

  • 0 in reply to Ralph Jacobi
    Intellectual 420 points

    Hello Ralph,

    Thanks for your answer. It's a help guiding us on the right direction.

    Is there a simpler way to do this that wouldn't require so much time and effort? For example, use a 25MHz crystal-based oscillator instead of simply a 25MHz crystal on OSC1 and OSC2?

    Best,

    Eduardo Barcellos

  • +1 in reply to Eduardo Barcellos
    TI__Guru*** 135355 points

    Hello Eduardo,

    It's possible to use a simpler setup as described in our System Design Guidelines: https://www.ti.com/lit/pdf/spma056

    It is possible to use a single-ended clock source such as an external oscillator to drive the OSC0 input of the Main Oscillator Circuit. Refer to the device's data sheet for input specifications. When a single-ended clock source is used, the OSC1 pin should be left unconnected and GNDX2, if present, should be connected to GND

    I mention the due diligence simply because you have said you have had issues with getting that working with the Ethernet controller - so trying to guide you on the right steps to take to build out a robust solution.

    Best Regards,
    Ralph Jacobi