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MSP430FR5969: GPIO pad high impedance current

Koichiro Tashiro
Mastermind 22945 points
Part Number: MSP430FR5969

Hi,

My customer who is evaluating MSP430FR5969 has a question for GPIO pad impedance.
According to Datasheet table 5-11, High-impedance input leakage current is +/-20nA.

But if customer measured it on their custom board, the leakage seems much higher.
For example, if customer put an external pull up(3.0V) with 1M Ohm on P4.7 or P1.3, the voltage drops to ~2.7V.
Please note that the pin is open(nothing other than pull-up and 0.1uF capacitor are connected).
If an external pull-up value is changed to 100kOhm, the voltage is ~3V.

What is causing such behavior?

Thanks and regards,
Koichiro Tashiro

  • 0
    TI__Mastermind 29386 points

    Hi Koichiro,

    The high-impedance state of the GPIO port is implemented by a schmitt trigger, so there will be leakage current, as you describe: -20na-+ 20na.

    Thus if you pull up a large resistance, this situation will occur. Generally, it is recommended to around 10K Ohm.

    By the way, why does the customer pull up a 1M Ohm resistor?

    Best Regards

    Johnson

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