TCA9539: RESET unstable

Kevin Huang8

Part Number: TCA9539

Tool/software:

Hi Team,

I found that sometimes pin24 RESET- this pin is sometimes disturbed (ex. external chamber switch),
This causes the IC to enter the reset state by mistake, clearing the originally set GPI/GPO state.
In our experiment, if we change R882 from 4.7K to 0ohm, it will not trigger reset by mistake.
I just wonder if there might be any other problems?

3 months ago

0 Tyler Townsend 3 months ago

TI__Mastermind 47188 points

Hi Kevin,

If you change R882 from 4.7k to 0ohm, you will run into issues when attempting to toggle /RESET LOW from the MCU GPIO. You might burn up the GPIO from it pulling LOW and a 0 ohm resistor to VCC. It essentially looks like a pwr-gnd short.

My recommendation is to add an external cap at the pin to keep charge on /RESET during electrical disturbances from external switch.

Regards,

Tyler

0 Kevin Huang8 3 months ago in reply to Tyler Townsend

Genius 4495 points

Hi Tyler,

We have tried changing R882 from 4.7Kohm to 1Kohm and it also can clamp noise; is this a better solution?

0 Tyler Townsend 3 months ago in reply to Kevin Huang8

TI__Mastermind 47188 points

Hi Kevin,

This seems acceptable since 1k will limit current way more than 0 ohm + 33 ohm series resistance coming from GPIO_12.

This should limit the current to ~1-2 mA since VCC = 1.8V.

Regards,

Tyler

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TCA9539: RESET unstable