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CC2652R: MEMS oscillator

Carolus Andrews
Mastermind 25765 points

Part Number: CC2652R
Other Parts Discussed in Thread: CC1312R

Team,

Is it possible to use a single ended output MEMS oscillator to replace the crystal on the device?

  • 0
    Guru 735695 points
    It's not supported. You can refer to the discussions in e2e.ti.com/.../2447961
  • 0 in reply to YiKai Chen
    TI__Guru** 106705 points

    Well, since Siri posted that answer a year ago things have changed. While we are not supporting it yet, we are working on enabling TCXO support, which is what is being asked for here. We still have some validation to do before we can provide this option, but unless we meet any problems, this should be available by the end of Q3.

    Generally though, there is no need for anything more accurate than a typical crystal for the CC2652R though. TCXO would only be required for narrowband operation typically at sub-1 GHz frequencies.

    Regards,
    Fredrik

  • 0 in reply to Fredrik K
    Guru 735695 points
    Cool! Look forward to seeing the improvement.
  • 0 in reply to Fredrik K
    TI__Guru** 106705 points
    Hi Carolus,

    Thanks for sharing the information about this being for a high-G application. In such applications MEMS oscillators may definitely be better suited than crystals.

    Since this is currently work in progress, we do not have the right driver functions available yet to enable this mode properly in the device.

    From a HW design point of view, you can look at the CC1312R LaunchPad.

    Regards,
    Fredrik
  • 0
    TI__Mastermind 25765 points

    Part Number: CC2652R

    Team,

    I have a few follow up questions from the referenced post:

    - When the changes Fredrik mentioned become supported in Q2, are these driver changes implemented in the stack, i.e., SW, or are these drivers that will update the silicon?

    - Based on the HW of the CC1312, I see TCXO support is for the larger crystal. Will a 32.768 kHz TCXO similarly be supported on the low-power XTAL input at any point for the C2652R?

  • 0 in reply to Carolus Andrews
    TI__Guru** 106705 points
    Hi Carolus,

    I merged the latest post into the original thread since they are on the same topic.

    - I have revised my time estimate to end of Q3. These are SW changes, no HW changes are required.

    - TCXO is already supported for the 32 kHz clock. This is documented in the TRM and configured in CCFG. Input is through a GPIO.

    Regards,
    Fredrik
  • 0 in reply to Fredrik K
    TI__Mastermind 25765 points
    Fredrik,

    Sorry to be a pain, but I've had a look at the TRM, and its not immediately apparent what I would need to do to configure this via the CFCG registers. Could you briefly walk me through what needs to be done to set this up?
  • 0 in reply to Carolus Andrews
    TI__Guru** 106705 points

    Carolus,

    CCFG:MODE_CONF.SCLK_LF_OPTION and CCFG:MODE_CONF.EXT_LF_CLK are the registers you are looking for.

    This is done through ccfg.c which has a more easily read formatting:

    //#####################################
// Clock settings
//#####################################

#ifndef SET_CCFG_MODE_CONF_SCLK_LF_OPTION
// #define SET_CCFG_MODE_CONF_SCLK_LF_OPTION            0x0        // LF clock derived from High Frequency XOSC
// #define SET_CCFG_MODE_CONF_SCLK_LF_OPTION            0x1        // External LF clock
#define SET_CCFG_MODE_CONF_SCLK_LF_OPTION               0x2        // LF XOSC
// #define SET_CCFG_MODE_CONF_SCLK_LF_OPTION            0x3        // LF RCOSC
#endif

#ifndef SET_CCFG_EXT_LF_CLK_DIO
#define SET_CCFG_EXT_LF_CLK_DIO                         0x01       // DIO number if using external LF clock
#endif

    Regards,
    Fredrik