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CC2540 on 6V with ADC

Demie Baltazar
Prodigy 70 points
Other Parts Discussed in Thread: CC2540

Hi Good day everyone, Im using 6 volts (4 AA batteries)to power my CC2540, and i want to get the ADC and Battery Level of my power source. On my testing i always got 100%(Battery level) from 6V down to 3 Volts and it will just change if my power source is lower than 3 volts.   Based on the source code the maximum that was used is 3 volts.  What are the things i need to update/edit/change  just to measure the adc and batt level for 6volts. 

Thank you in Advance.

Demie

  • 0
    Guru 735685 points
    It is not possible to make CC2540 accept 6V as ADC input. You have to creates a voltage divider circuit to divide battery voltage to an acceptable level.
  • 0
    TI__Mastermind 29650 points
    Demie,

    6V input is far above absolute maximum ratings for the CC2540 device. Do you have a divider in place after the 6V source or are you inputting the signal directly to the chip?

    Regards,
    svend
  • 0 in reply to svendbt
    Prodigy 70 points
    Hi svendbt,
    No i dont put it directly, it pass by a regulator...

    Regards,
    Demie
  • 0 in reply to Demie Baltazar
    TI__Mastermind 29650 points
    Demie,

    If you measure the output of a regulator you should of course measure a constant voltage, that is the purpose of the regulator.
    When you see the regulator voltage go below 3V it is because the (buck) regulator is no longer able to supply the specified voltage.

    If you need to measure the 6V battery voltage you need to add a resistive divider + decoupling capacitance as a separate input to the ADC.
    Since you are using the regulator also below what it is specified (and end up with a non-constant chip supply) you should probably use the internal 1.2V reference while doing your measurements.