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LFXT1Sx configuration mismatch to actual crystal frequency

Other Parts Discussed in Thread: MSP430F2131

Hello,

I'm using an MSP430F2131. I want to set the LFXT1Sx for a 1-3Mhz crystal for lower power consumption. The actual crystal is however 4Mhz.

Can anyone tell me what the consequences are of this mismatch, if any?

Thank you in advance,

Michael

  • The only consequence (in this case) is, that you don't save as much power as you could.

    The main difference in the settings is that higher frequency crystals require a higher power injection by the oscillation driver. For slower crystals this may be reduced. So if you run on the 4MHz setting, you waste some power, but I don't expect any other consequences.

    In the opposite case, it is possible that the crystal oscillation will cease or will be not stable or at a wrong frequency because of a too-low driver strength.

  • If I understand correct, my case is the "opposite case" (i.e. 4Mhz crystal wil low frequency setting). Which if I understand correct would result in a lower power injection than necessary with instabilliy and wrong frequencies as a result.

    Thank you for your answer

  • Yes, you're right.
    I undestood your initial question in a way that you're using a 4MHz crystal right now by want to replace it by a slower one (without changing the code). Which would of course save much power. :)
    It might work anyway. It completely depends on the crystal and the quality (ESR) of the used capacitors. If you use very-high quality capacitors and a good crystal, the lower settings might work without problems.
    But I wouldn't risk it. If you build another device later, you'll probably won't get the same quality components or even forget about that and wonder why it doesn't work.