• State Resolved
  • Locked Locked
  • Replies 1 reply
  • Subscribers 33 subscribers
  • Views 106 views
  • Users 0 members are here
Support feedback
Options
Options
Related

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.

TCA9555: Input State Retention Without I2C Host Power

Grzegorz Wozny
Prodigy 10 points
Part Number: TCA9555


Tool/software:

Hi everyone,

I’m using the TCA9555RTWR I/O expander in my design and I have a question regarding its behavior in the following scenario:

Does the TCA9555 retain the logic level on its input / outputs pins if the I²C host MCU is reset or completely powered down (VCC of the MCU is disconnected), assuming the TCA9555 itself is still powered?

In other words, can I still read the correct input / outputs states later via I²C (once the MCU comes back online), or will the inputs float or change internally?

Thanks in advance for any clarification!

  • +1
    TI__Guru 53958 points

    Hi Grzegorz,

    As long as the TCA9555 has sufficient power on VCC as to not trip the power-on-reset (I think datasheet says <= 1.2V trips a PoR), then the TCA9555 would retain its state on the I/O's. 

    The TCA9555 only goes back to default conditions on a power-on reset, or when the TCA9555 internal registers are configured through the I2C bus. 

    Regards,

    Tyler