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Pullup and pulldown on CC2650

Vikash Siva18
Prodigy 50 points
Other Parts Discussed in Thread: CC2650, CC2560

On the technical reference manual page 879 for CC2650 it is mentioned as "Pullup and pulldown resistances are given in the data sheet".

 

Looking at the datasheet for CC2650 I was not able to find the resistor value. All I can able to see is the GPIO pullup current  277uA and GPIO pulldown current  113uA .

 

Could you please let us know the resistor value. 

  • 0
    TI__Mastermind 18780 points
    Hi,
    The pull values are dependent on the supply voltage on CC26XX. You can calculate the pull resistance by using the pullup/pulldown current for 1.8V / 3.8V in the "DC characteristics" section of the data sheet.
  • 0 in reply to CHS
    Prodigy 50 points
    Using the DC characteristics the values I got are for 3.8V pullup resistance is 13.718Kohm, pulldown resistance is 33.628Kohm. For 1.8V pullup resistance is 25.104Kohm, pulldown resistance is 85.30Kohm. The variation on the resistance value is I suppose because of pullup and pulldown current.
    Can I please know why there is a variation on the current vales for 1.8V and 3.8V? I am using 2.8V in my design. So What would be the pullup and pulldown current. ? How do I calculate the resistance value ?
  • 0 in reply to Vikash Siva18
    Guru 16361 points

    I've just hit the same issue. The datasheet for CC2560 gives four pull current values which are inconsistent, implying four different resistances as Vikash wrote above.

    Does the pull resistance somehow vary with voltage (in addition to the current variation you'd expect from V=IR)? If so, what's the method used to calculate the pull resistance at different voltages?

    I'm also unclear on why the resistance would differ for pullup vs pulldown at the same voltage. For the MSP family the same resistance is specified for both directions.

  • 0 in reply to Robert Cowsill
    TI__Guru** 106705 points

    Hi Robert,

    Yes, there are large variations over operating conditions for the pull ups and -downs. If you need accurate pull, for example for I2C, it is recommended to use external resistors.


    Cheers,
    Fredrik

  • 0 in reply to Fredrik K
    Guru 16361 points
    Hi Fredrik,

    I'm not looking for an accurate pull value, but I'd like to get a conservative estimate of maximum power consumption through an internal pull resistor. My application is powered by a 3V coin cell, but a value for maximum (not typical) pull current at 3.8V would probably suffice.

    Thanks, Rob