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CC2640R2F: States of unused X32K_Q1 and X32K_Q2 output pins?

Jonathan Drake
Prodigy 90 points
Part Number: CC2640R2F

On CC2640R2F, if X32K_Q1 and X32K_Q2 are not being used:

  1. What are the default states of X32K_Q1 and X32K_Q2 pins; for example, do they remain as input & output respectively, or do they become hi-Z?
  2. Can X32K_Q1 and/or X32K_Q2 be configured to hi-Z or 0 states?
  3. Can X32K_Q1 and/or X32K_Q2 be configured such that they can be externally connected to GND?

Regards,

Jonathan

  • 0
    TI__Guru 58425 points
    Hi Jonathan,

    I would expect them to be left floating but I need to double check that. Why would you like to run without the 32K crystal in this case? It is highly recommended to run with an external crystal for protocols such as BLE.
  • 0 in reply to IUsedToBeARealPerson (M-W)
    Prodigy 90 points
    Hi M-W,

    Thank you for the quick response. I look forward to the clarification.

    The 32kHz crystal is not used because it is unnecessary in the application.

    Kind regards,


    Jonathan
  • 0 in reply to Jonathan Drake
    TI__Guru 58425 points
    Hi Jonathan,

    It is acceptable to both leave the pins unconnected or grounding them, the recommended practice is to leave them floating. You don't really have control to configure the state of the pins when not used.

    Out of curiosity, as you are using the CC2640R2, what is your application?
  • 0 in reply to IUsedToBeARealPerson (M-W)
    Prodigy 90 points

    Hi M-W,

    Thank you for confirming how the pins can be connected.

    If both pins are connected to ground, is there any additional current draw when the device wakes from shutdown? 

    Although it doesn’t directly affect my present application, I note that Application Report “SWRA499B–June 2016–Revised April 2017” which apparently covers CC2640R2F states in section 3.1:

    “The 32 kHz crystal pins will be in a Hi-Z state when not used and can safely be tied to any logic level, or left unconnected.”

    However, if the logic levels are greater than 2.25V, as would be the case in many systems (typically VDDS >2.25V), then according to the CC2640R2F datasheet “SWRS204A –DECEMBER 2016–REVISED JANUARY 2017” the Absolute Maximum Rating of the crystal pins would be exceeded.

    Is the datasheet or application report correct? Or maybe my information is out of date?

    My application is a medical device.

    Kind regards,

     

    Jonathan