This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

TCA9539-Q1: The output pin of TCA9539 appears high level during power-on.

Part Number: TCA9539-Q1
Other Parts Discussed in Thread: TCA9539

I configured the pins of TCA9539 as outputs.

I found that when the chip is powered on, all output pins will have a high level for a short time.

What is the cause? Will it interfere with external loads?


  • Hi User,

    I suspect this is because you are configuring the configuration register first before configuring the output register. You should be able to solve this by configuring the output registers first to their desired state then setting the configuration register.

    Let me know if you have further questions or if you still weren't able to resolve the issue after double checking/making the change in software.