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CC2540: Chip Behavior and Expected current draw below 2V (Latch Condition)

Nihar Patel
Prodigy 40 points
Part Number: CC2540

The datasheet mentions device operating voltage range is 2-3.6V. Can we know what is the device behaviour below 2V? (Especially wrt current draw and application code behaviour)

  • We have tested our device for this condition and we have seen constant current demand below 1.9V. 
  • We have a battery powered application and during transmission battery voltage goes below 2V.
  • We are trying to understand, what time period of a low voltage pulse can trigger Latch condition?
  • Is there a way to prevent a device from going into this condition? (Preferably Software Solution)

Also, there is a need to understand Chip to Chip variations of CC2540, since we are using it in a production environment we need to check the reliability of the device. What kind of Data TI can provide for this?

  • 0
    TI__Guru** 106705 points
    Hi Nihar,

    Below 2.0 V the BOD will trigger and hold the device in reset. BOD reset will be released if the voltage increases above 2.0 V again. The BOD will trigger immediately, there is no timing threshold.

    Regards,
    Fredrik
  • 0 in reply to Fredrik K
    Prodigy 40 points
    Thanks for faster response Fredrik,

    It holds true with Power supply, I have seen device going in/out reset near 2V.
    But this does not seem to be the case with Battery.
    We have seen constant current draw once the voltage crosses below 2V. I believe it can be the battery not gaining voltage back due to complete discharge.

    Is it possible to detect this reset ? is there any flag which gets triggered? if that's the case some logic limiting transmission should extend the life of the device.

    Regards
    Nihar
  • 0 in reply to Nihar Patel
    TI__Guru** 106705 points
    Hi Nihar,

    Typically when running off battery there will be no return once the voltage crosses 2.0 V. The device will then be held continuously in reset and the current consumption will be constant. Once the voltage crosses below approximately 1.6 V, the current consumption will be limited to 50 uA to prevent alkaline batteries from leaking.

    There is no way to detect the reset once it has happened since the application code is not running in this condition. If you need to detect that the battery voltage is close to being depleted, you must measure it regularly with the internal ADC.

    Regards,
    Fredrik