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MSP432P401R: 48MHz crystal in MSP-TS432PZ100 Rev 1.3

Yu-Hung
Expert 1130 points

Part Number: MSP432P401R

Hi

I am learning MSP432P401R and reading MSP432™ SimpleLink™ Microcontrollers Hardware Tools User's Guide (Rev. B)

http://www.ti.com/lit/pdf/slau571

I have some problem about the crystal.

In the datasheet of MSP432P401R, The recommended operating conditions of HXFT is...

But in MSP-TS432PZ100 Rev 1.3 Target Socket Board...

Q3 is CRYSTAL 48.00 MHZ 12.0PF SMD (EPSON FA-238 48.0000MB-W0, support.epson.biz/.../doc_check.php

ESR = 40 ohm, CL = 12pF

According the equation : CL = ((C x C) / (2 x C)) + Cstray(2pF~5pF)

 

Question 1) ESR of Q3 is not fitting in recommended operating conditions. why?

Question 2) C=22pF is C_HFXT? 

Question 3) Why TI use C=22pF on the board?

 

Any response would be helpful, thanks for the time you spent to read this post.

PS.

Some figures in the document like this...What does that mean?

  • 0
    TI__Mastermind 38930 points
    Yu-Hung,

    I've reached out to someone who can help you with this topic. Please allow a bit of time for them to look into this and respond accordingly.
  • 0 in reply to Evan Wakefield
    TI__Mastermind 21605 points

    Hi Yu Hung,

    The reason the crystal used in the MSP-TS432PZ100 target socket board doesn't completely match the datasheet specs is that including the socket in the board design drastically changes the crystal behavior due to the increased signal path on the PCB and through the socket itself.  We did some testing and found the crystal and load capacitors shown in the design function as expected in the target socket board, so we used it.  The target socket board is not intended to be a reference design for crystal layout, but instead a platform that allows all possible functionality of the device.

    When designing a custom PCB, we recommend following the specs set in the datasheet.  Also, take a look at the MSP 32kHz Crystal App Note.  While the app note specifically targets 32kHz cyrstals, there is still a lot of information that applies to any crystal circuit.

    Mike

  • 0 in reply to Mike Pridgen
    Expert 1130 points

    Hi Mike,

    Thanks for your reply.

    Actually TI use the same crystal in MSP432P401R LaunchPad™ Development Kit.

    The MSP-EXP432P401R Hardware Design Files was found in following link.

    http://software-dl.ti.com/msp430/msp430_public_sw/mcu/msp430/MSP-EXP432P401R/latest/index_FDS.html

    The crystal is 48.00 MHZ 12.0PF SMD, Digikey FA-238 48.0000MB-W0-ND.

    The LaunchPad does not use socket.

    YHH

  • 0 in reply to Yu-Hung
    TI__Mastermind 21605 points
    Hi,

    The LaunchPad uses the same crystal based on some other internal decisions that were made. We tested and verified functionality of that specific crystal for the intended operating conditions of the LaunchPads (i.e. room temp, etc) and were happy with the performance. We recommend following the specification in the datasheet for custom boards to guarantee functionality. If you would like to put a device outside of our recommendations on your design, it is up to you to verify you are ok with the performance.

    Thanks,
    Mike
  • 0 in reply to Mike Pridgen
    Expert 1130 points
    Hi Mike,

    Thanks.

    BTW, how is the Figure 1-10?

    I have no idea how they mean.

    YHH
  • 0 in reply to Yu-Hung
    TI__Mastermind 21605 points

    Hi,

    Figure 1-10 shows the assembly drawing of the part.  The image you posted above seems to be glitched somehow.  The actual image is shown below.  If the above is what your downloaded version of the pdf, you may want to re-download the pdf.

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