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MSP430FR5969-SP: External HFXT Clock Configuration

Jordan W
Prodigy 10 points
Part Number: MSP430FR5969-SP

Hello,

I'm looking to use the MSP430FR5969-SP for a space flight product which requires radiation hardened components. The MSP430FR5969-SP has the HFXT input for a tuning fork crystal, but there does not appear to be radiation hardened tuning fork crystals on the market. However, by setting HTFXTBYPASS=1, will I be able to send an external oscillator clock signal into HFXT (at 3.3V, 4MHz, CMOS or TTL)? If this can be functional, then how should the connections be made between the external oscillator and the HFXT pins (resistors, etc.)?

Lastly, I added an attachment of the external oscillator (4MHz) which I'm inquiring about compatibility with the MSP430FR5969-SP.

Regards
XE61S-L00.pdf

  • +1
    TI__Guru 56685 points

    Hello,

    If using HFXT input in bypass mode, you need to ensure it follows the Schmitt-trigger input levels defined in section  of the datasheet, and the HFXT in bypass mode specs in Table 4-5. Typically, these type of connections do not need any passives and connect directly into the device, but always follow your device's manufacturer's recommendations. 

  • 0 in reply to Jace H
    Prodigy 10 points

    Thank you Jace. To clarify, are the Schmitt-trigger input levels defined in "Table 4-11. Digital Inputs"? Are the positive-going and negative-going input thresholds from that table the same as the "Schmitt-trigger levels"?

  • +1 in reply to Jordan W
    TI__Guru 56685 points

    Correct, Table 4-11. 

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