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MSP432P401R: MSP432P401R LaunchPad Crystal

Jiacheng Jason He
Prodigy 130 points

Part Number: MSP432P401R

Hi! I am a student working on my senior capstone project at UT Austin, and our team is trying to use the MSP432P401RIPZR chip for a custom PCB design. I was looking at the hardware resources and the BOM, and tried to find the high frequency 48 MHz crystal that is used on the LaunchPad, but the product from DigiKey can only be purchased in bulk (1000+).

DigiKey offered the following alternative (linked). It looks like it should be more stable, same load capacitance, but the ESR is 50 Ohms, instead of 40 Ohms. I know the crystal and capacitors surrounding it are a delicate system; do y'all think that this alternative will work?

  • 0
    Guru 46710 points

    [edit] According to datasheet Table 5-9. High-Frequency Crystal Oscillator, HFXT, Recommended Operating Conditions, ESR shall be no more than 30 Ohms. Pehraps 40 will do ok, but 50 Ohm could be too much

  • 0 in reply to Ilmars
    Prodigy 130 points
    Hm, okay! Looking at 5-9, though, I'm a bit confused, since it seems to imply that at 48MHz max ESR should be 30 ohms, but the LaunchPad part on the BOM is at 40 ohms.
  • 0 in reply to Jiacheng Jason He
    Guru 46710 points
    Sorry, about changing my mind couple of times :) As Launchpad is not specified for industrial temperature range, TI could decide to use cheaper crystal which works well for launchpad, but maybe not OK for whole temperature range. After all TI knows more than is written in the datasheet. So please stick to documentation, not components which are used on development boards.
  • 0 in reply to Ilmars
    Prodigy 130 points

    Hmm, thanks for the info! Didn't see that in the datasheet before.

    I still don't know what crystal to use, though. :( I can't seem to find anything on DigiKey, Mouser, Newark, Arrow, etc. that fits the specs. It's hard enough to find a 40 Ohm ESR part; I can't find any 30 or 15 Ohm crystals.

    If anyone knows of any stock crystals that should work, I would greatly appreciate it! :)

  • 0 in reply to Jiacheng Jason He
    Guru 46710 points

    Jiacheng Jason He said:
    I still don't know what crystal to use, though. :( I can't seem to find anything on DigiKey, Mouser, Newark, Arrow, etc. that fits the specs. It's hard enough to find a 40 Ohm ESR part; I can't find any 30 or 15 Ohm crystals.

    Are you going to design mass-product for industrial temperature range? If not - then you can relax requirements, especially if you plan to build prototype first.

  • 0 in reply to Ilmars
    Prodigy 130 points

    Not for mass production, just this one-time project. Do you think the 50 Ohm ESR one will work? I ordered a couple since they were cheap, so I might give them a try. Will update if they do.

    Thanks for your help!

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