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TMS320F28027F: Can GPIO's be held low during power on?

Wayne Hughes
Prodigy 30 points

Part Number: TMS320F28027F

Hello,

I'm using GPIO 29 on this microprocessor to control an in-rush circuit.

The circuit is an open collector to drive an optocoupler to an IGBT. 

The IGBT shorts out an in-rush power resistor once the capacitors are mostly charged.

During power on of the microprocessor this GPIO is low, then goes high for about 25mSec before going low.  It then turns on correctly once the capacitors are charged.

Is there a way to keep this GPIO low during power on?  Are any of the GPIO's low during power on?

Thanks.

  • 0
    TI__Mastermind 42195 points

    Wayne,

    please see the following excerpt from the Datasheet.

    For the default value of the Pull up resistor please look at the GPxPUD register's default value, 0= active 1= inactive on startup. 

    To keep the GPIO in a known state you should add a pull-down resistor externally to the device. Ideally you will choose a GPIO without the pull up enabled by default, but the internal pull up is weak and can be overpowered by an external resistor. 10K ohms works for many applications for noisy applications 2.2K is recommended, but you will need to evaluate your system and determine the best value.

    Regards,
    Cody