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TMS320F28062: How to disable pull-up activation on reset

Pierre Lorent
Prodigy 190 points
Part Number: TMS320F28062


Hi all,

I fear the answer is no, but I prefer not to miss a potential solution. We discovered recently that the internal pull-ups of the TMS320F28062 uC have not been taken into account when designing a digital output circuit.

Per the datasheet, it is enabled when the devices reset, including due to POR and BOR. This causes glitches at power on and off.

Is there any way (configuration btis or whatever) to change this behavior such that the pull-up's do not reactivate at every power on and off ?

Thanks.

  • 0
    TI__Guru 61235 points

    Pierre,

    Unfortunately, No.  You cannot change the default internal pullup behavior.  This is hardwired in the device design.

    Regards,

    David

  • 0
    TI__Mastermind 42195 points

    I concur with David.

    I would like to add that you can add an external Pull-up/down resistor to overpower the internal pull up.

    Regards,
    Cody

  • 0 in reply to Cody Watkins
    Prodigy 190 points

    Hi,

    Thanks for the confirmation. We thought of adding the pull-down but have to validate it will not stress too much the device and its supply. Per the specifications :

    As the outputs drives transistors we need a very low voltage (<0.3), meaning a small resistor pull-down like 1k (1k * 200 uA = 0.2 V) to avoid the issue but and an extra consumption on normal high level of 3.3 mA * 4 affected outputs. Will need some fine tuning and validation.

    In the electrical specification they also mention an internal pull-down, but in the datasheet I cannot find any reference to it. Am I right that it is because other families of uC have some but this one does not have any ? I find it strange because the electrical spec document refers specifically to this uC family.

  • 0 in reply to Pierre Lorent
    TI__Mastermind 42195 points

    Pierre,

    Pierre Lorent said:
    In the electrical specification they also mention an internal pull-down, but in the datasheet I cannot find any reference to it. Am I right that it is because other families of uC have some but this one does not have any ?

    This MCU does have in internal pull-down, to the best of my knowledge its only used on special pins like TRSTn, not GPIO.

    Regards,
    Cody 

  • 0 in reply to Cody Watkins
    Prodigy 190 points

    OK, was not thinking of special pins. Thanks.