PCA9555: External Pull-down

Shuji Ishiwata

Part Number: PCA9555
Other Parts Discussed in Thread: TCA9535, PCA9535

Hi All,

I have a question about PCA9555.
The I/O terminal is pulled up internally, but I want to set it to Low immediately after PowerOn.
Is it okay to add a 10kΩ pull-down externally?

Best Regards,
Ishiwata

over 3 years ago

0 Clemens Ladisch over 3 years ago

Guru 319890 points

Yes. This will result in a voltage divider, but about 9 % of V_CC is probably low enough for you.

Consider using an I/O expander without internal pull-ups, e.g., PCA9535/TCA9535.

0 Shuji Ishiwata over 3 years ago in reply to Clemens Ladisch

Mastermind 8220 points

I was using PCA9535, but I am considering PCA9555 because of the late delivery date.
thank you for your reply. I would like to lower the resistance value a little more and lower the Low level.
Thank you for your support.

0 Chris Ayoub over 3 years ago in reply to Shuji Ishiwata

TI__Genius 15345 points

Hi Shuji,

We have some inventory of the TCA9535. This would be a more compatible drop in solution to the PCA9535. How many devices do you need?

Also when lowering the pull down resistance make sure that you do not exceed the recommended current specs of the device:

Best,

Chris

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PCA9555: External Pull-down