TCA6418E: unused GPIOs of TCA6418EYFPR

yaseer zakaria

Prodigy 120 points

Part Number: TCA6418E

Dear Team,

Good day!!

TCA6418EYFPR has 18 GPIO's, can i tie the unused GPIOs permanently to GND without any external pulldown resistor.

over 5 years ago

0 Miguel Robertson over 5 years ago

TI__Guru 62920 points

Hello Yaseer,

Yes, this is OK to do. Just make sure you don't configure the IOs as high-state outputs, since that would result in high currents to flow. Please let us know if you have any other questions.

Max

0 yaseer zakaria over 5 years ago in reply to Miguel Robertson

Prodigy 120 points

Dear Max, Many thanks for your reply.

I plan to use 4.7k pullup resistor on the I2C lines and will operate at max 400khz.

Do you see any issue in it.

Need your suggestion.

0 Miguel Robertson over 5 years ago in reply to yaseer zakaria

TI__Guru 62920 points

Hello,

That may or may not be OK depending on how much parasitic capacitive loading there is. The rise time of the I2C signal would be determined by the RC time constant of this load capacitance and the pull-up resistance, and you would want to make sure it meets the requirements defined for 400 kHz. You can read more in this app note:

http://www.ti.com/lit/an/slva689/slva689.pdf

In particular, Figure 3 should be useful to you in understanding the maximum pull-up that can be used for different capacitive loads for both 100 kHz and 400 kHz operation.

Regards,
Max

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TCA6418E: unused GPIOs of TCA6418EYFPR