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CC2340R5: Which applications use 32k crystals

wangrenli
Intellectual 690 points
Part Number: CC2340R5

Hi,

For what applications is the 32kHz crystal oscillator's clock used (I only know it's used with the RTC function, but I am not using the RTC function). If I want to save costs and use an internal 32kHz oscillator, what impacts would there be, and how should I verify its feasibility?

thanks

  • 0
    TI__Guru**** 171004 points

    Hi,

    Across our family of devices, Bluetooth LE being used as a central device requires tighter tolerances than what is provided by the internal RC oscillator - this is critical to establish connections with peripherals. In other words, if you intend to use the device as a central Bluetooth LE, you must use a LFOSC XTAL.

    However, specifically for CC2340R5, please check the errata CLK_01 as it covers the use of the RC oscillator and a suitable workaround.

    Hope this helps,

    Rafael

  • 0 in reply to desouza
    Intellectual 690 points

    Hi,

    According to the documentation, this feature is supported in versions of the SDK ≥ 8.10. I am currently using the SDK "simplelink_lowpower_f3_sdk_7_40_00_64", does this version already support it? Additionally, I have a project that uses the "connection_monitor" project, can this also use the internal crystal oscillator?

  • 0 in reply to wangrenli
    TI__Guru**** 171004 points

    Hi,

    wangrenli said:
    does this version already support it?

    No. Sorry. It will be supported in an upcoming version.

    wangrenli said:
    I have a project that uses the "connection_monitor" project, can this also use the internal crystal oscillator?

    Given the connection monitor requires to keep a close track of the traffic between the two Bluetooth LE nodes and transitions through low power states, the external LFXTAL is required.

    Regards,

    Rafael

  • 0 in reply to desouza
    Intellectual 690 points
    desouza said:
    No. Sorry. It will be supported in an upcoming version.

    Hi,

    I did a test of connecting and transmitting data with an internal 32k crystal, no packet loss for 12k/s transmission in both directions, and no disconnections for 24H after connecting, and no other anomalies with my current version of the sdk except for a few microamps greater power consumption. Is this considered viable.

  • 0 in reply to wangrenli
    TI__Guru**** 171004 points

    Hi,

    As you can imagine, when we perform the characterization of our devices and its internal peripherals, we always need to take into consideration the temperature and power supply ranges, as well as the normal part variability that comes with large scale manufacturing. That is why I can't assume viability on a single test done at a customer's site using a custom designed product, especially if it is being used outside of the documented specifications given on a datasheet or TRM.

    So, if you know the usage conditions of your product will always match your test environment, then I suggest thoroughly validating your products and assuming the risk of using the device in this manner. 

    Best regards,

    Rafael