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MSP430FR2476: Acceptable frequency range for XT1 in bypass mode

Jonathan Navor
Genius 9475 points

Part Number: MSP430FR2476

Hi Team,

Good day! We need your assistance to clarify information with MSP430FR2476.

Our customer is considering using an external clock input to the MSP430FR2476 using XT1 input in bypass mode, i.e. supplying a square wave (from another MCU).  We could not find any limits to the acceptable frequency range in the data sheet, only a "typical" figure of 32.768 kHz.

The other MCU can output a frequency with a period of 25 microseconds, equivalent to a frequency of 40 kHz.  (This other MCU is crystal controlled, so this frequency can be considered "accurate".)  Is this too fast for the MSP430FR2476?

In case there is some variation in the input clock frequency, e.g. +/- 1%, then the frequency could rise to 40.4 kHz.  Is this too fast?  What is the practical limit?

Thank you in advance for your support

Best regards,

Jonathan

  • 0
    TI__Mastermind 28105 points

    Hi Johnathan,

    The Clock Distribution Table from the device datasheet includes the limits of XT1 as DC up to 40kHz.

    Jonathan Navor said:
    In case there is some variation in the input clock frequency, e.g. +/- 1%, then the frequency could rise to 40.4 kHz.  Is this too fast?  What is the practical limit?

    They would probably be fine if they are really +/-1%, but it is outside of the specification on XT1 and would be outside our characterization, so we couldn't guarantee it. 40Khz and below would be our recommendation for XT1 on this device.

    Best Regards,
    Brandon Fisher

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