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OMAP-L137 GPIO internal pullup

Chikku
Intellectual 805 points
Other Parts Discussed in Thread: OMAP-L137, OMAPL138

Hi,

  As you know OMAP-L137 has I/O pins with internal pulldown or pullup resistor,
  what is the value of these internal resistors,
  and what external pull down resistor value would you suggest when opposing internal pull up.

Thankyou and Regards.

  • 0
    TI__Expert 6000 points

    Hi,

    The OMAPL137's pull-up/downs should be similar to those of the OMAP138. (In the process of double checking this to make sure...)

    Please see the following thread for additional discussion.

    [OMAPL138]  Resistance Specification for Internal Pull-Up and Pull-down Resistors
  • 0 in reply to Michael Questo
    TI__Expert 6000 points
    OMAPL137 DS - http://www.ti.com/lit/ds/symlink/omap-l137.pdf
     
    Section "4.2 Recommended Operating Conditions" in Datasheet
    Recommended I/O Operating Range (DVDD)
    3.3V I/O - 3.0V to 3.45V
    1.8V I/O - 1.71V to 1.89V
     
    Section "4.4 Electrical Characteristics Over Recommended Ranges of Supply Voltage and Operating Case Temperature"
    LVCMOS Pull-Up Current
    Min 30 uA
    Max 200 uA
     
    LVCMOS Pull-Down Current
    Min -50 uA
    Max -300 uA
     
     
    Resistance Calulations: Pull Down
    Resistance Pull Down 3.3V I/O:
    Max : 3.00V / 50 uA = 60k
    Min : 3.45V / 300 uA = 11k
    Typ : 3.30V / 175 uA = 18.85k
     
    Resistance Pull Down 1.8V I/O:
    Max : 1.71V / 50 uA = 34.2k
    Min : 1.89V / 300 uA = 6.3k
    Typ : 1.80V / 175 uA = 10.3k
     
     
    Resistance Calulations: Pull Up
    Resistance Pull Up 3.3V I/O:
    Max : 3.00V / 30 uA = 100k
    Min : 3.45V / 200 uA = 17.25k
    Typ : 3.30V / 115 uA = 28.7k
     
    Resistance Pull Up 1.8V I/O:
    Max : 1.71V / 30 uA = 57k
    Min : 1.89V / 200 uA = 9.45k
    Typ : 1.80V / 115uA = 15.65k

  • 0 in reply to Michael Questo
    Intellectual 390 points
    How did you get 115 uA for the Resistance Calculations: Pull Up, Typ: 3.30V? I cannot find that value in any of the datasheets.