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msp43fg4619 pull up resistor

Gaston_Melo_Arg
Mastermind 7675 points
Other Parts Discussed in Thread: MSP430FG4619

Hi,

I want to use one pin of port 5 of the msp430fg4619 but doesn´t have pull up resistor, my question is, which is the value of the resistor that i can use ?

Thanks

Gastón

  • 0
    Mastermind 7675 points

    to clarify,  i want to use it as input pin (P5.6 and P5.7)

    Thanks

  • 0
    Guru 227245 points

    'I need shoes, what size should I buy?'

    Different question, same answer: "it depends".

    If you have a pot pin and want to pull it hight, the resistor must be low enough to allow the input current flowing into the port pin for a voltage on the resistor of the difference between pullup voltage and the port pins high voltage. See the Processor datasheet for details.

    If you connect other hardware to the line, it must be low enough to satisfy their input currents too.

    That is the maximum requirement. the minimum requirement is that the attached devices need to be able to pull the line down to the port pins low voltage level by swallowing the current from the pullup as well as the current frowing out of the port pin.

    The optimum value is in between. The rule-of-thumb is 'as high as possible" to preserve as much power as possible, and "as low as needed' to reduce receptibility for EMI influence. The usually used range for a pullup is 10k to 100k, but depending on the surrounding circuitry it might be as low as 100Ohm and as high as 1MOhm.

    Sorry, there's no final answer. That's the reason why manufacturers take the time to write datasheets. And why Engineers spend so much time reading them.

  • 0 in reply to Jens-Michael Gross
    TI__Mastermind 26380 points

    Gaston,

    To add to Jen's reply - you can find information on the voltage threshold levels in the Vol and Voh parameters in the D/s (pg30). This should tell you how much current you can source or sink Vs maintaining a high/low voltage on the pin.

    Also, 430 devices with intergrated pull-ups use 35K ohm typical.

    Regards,

    Priya

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