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MSP430FR2476: Which one is the correct capacitance value, document? or EVM?

Shunsuke Yamamoto
Expert 8141 points
Part Number: MSP430FR2476
Other Parts Discussed in Thread: MSP430FR2676

Hi experts,

Which one is the correct capacitance value for 32kHz crystal oscillator?

Regarding the attached document, CL1 and CL2 are 23pF based on the calculations. On the other hand, 12pF of C3 and C4 are connected to MSP430FR2476 on the EVM. 

slaa322d (1).pdf

Best regards,

Shunsuke Yamamoto

  • 0
    TI__Guru 71216 points

    Hi Shunsuke,

    According the slaa322d, the capacitor value depends on the crystal manufacturer's recommendation. 

    So assuming 12pF, then the formula would require (2) 22pF to satisfy this requirement.

    I looked up the crystal from the FR2476 BOM and find this device which says 12.5pF.  Based on this I would say the FR2476 Launchpad has wrong values.

    Let me check to the tools team to see if they can help clarify this.

  • +1 in reply to Dennis Lehman
    TI__Guru 71216 points

    I did a quick check on the MSP430FR2676 EVM (same as FR2476 but with captouch) and it uses 22pF (sorry if pic is blurry) which would correlate with what the document is saying.

    Here is a related E2E posting that may be helpful -> link

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