PCA9539: PCA9539

Jie Wang

Part Number: PCA9539

Hi,

What is the status of the I2C pins of PCA9539 when PCA9539 is not powered? ( the I2C bus is pull-up to another power rail)

We have lots of I2C devices on the board. We need to use one I2C bus to connect with all these I2C devices and PCA9539. Those devices are not in the same power rail as PCA9539.

My concern is if PCA9539 is not powered, will it impact the I2C reading&writing of other devices which is powered normally? If the I2C pin does not acts as High-Z when PCA9539 is not powered, it will impact the behavior of the whole I2C bus, right?

over 4 years ago

0 Eric Hackett over 4 years ago

TI__Guru 74252 points

Jie,

An applications engineer has been assigned this thread and will respond by tomorrow in CST. Thank you for your patience.

Regards,

Eric Hackett

0 BOBBY over 4 years ago

TI__Guru 72751 points

Hi Jie,

The PCA9539 will be Hi-Z when unpowered on the I2C pins.

I would also make note that the RESET pin has an errata called out in the datasheet, please make sure to review it.

-Bobby

0 Jie Wang over 4 years ago in reply to BOBBY

Prodigy 100 points

Hi, Bobby

If the PCA9539 is not powered, we hold RESET pin low, will the I2C bus be hold at reset status and no read/write action can be performed for the whole I2C bus?

0 BOBBY over 4 years ago in reply to Jie Wang

TI__Guru 72751 points

No, our device will be HI-Z.

-Bobby

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PCA9539: PCA9539