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stm32f429 GPIO input impedance

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harry123
Senior

‎2024-06-10 03:17 AM - last edited on ‎2024-06-10 03:22 AM by

Will there be any input impedence for the gpio's of stm32f429

If yes what is the value.

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Melc_dB
ST Employee

‎2024-06-10 06:53 AM - edited ‎2024-06-10 06:57 AM

Hello @harry123,

The GPIO impedance depends on the configuration. 

As you talk about "input impedance", I assume that GPIOs are configured in digital input or analog input, in this case GPIOs are High impedance if no pull(up or down) resistor activated.

GPIOs have internal 40kOhms pull-up and pull-down resistor that can be internally activated see Table 56 in stm32f429 datasheet : DocID024030.

Hope that answers your question

Best regards,

Melchior

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Melc_dB
ST Employee

‎2024-06-10 06:53 AM - edited ‎2024-06-10 06:57 AM

Hello @harry123,

The GPIO impedance depends on the configuration. 

As you talk about "input impedance", I assume that GPIOs are configured in digital input or analog input, in this case GPIOs are High impedance if no pull(up or down) resistor activated.

GPIOs have internal 40kOhms pull-up and pull-down resistor that can be internally activated see Table 56 in stm32f429 datasheet : DocID024030.

Hope that answers your question

Best regards,

Melchior

To give better visibility on the answered topics, please click on Accept as Solution on the reply which solved your issue or answered your question.
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Uwe Bonnes
Principal III

‎2024-06-10 11:04 AM

As input and without pull resistor and in the allowed input voltage range, the input impedance is the effectiv input capacitance.The F429 datasheet does not mention the typical input capacitance, but probably 5 pF is no bad guess.

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