Hello Ti,
Hopefully this is a suitable place for this report.
We have discovered what we believe to be a silicon issue with at least more recently Fabricated PCA9534 parts.
The polarity inversion register (register 2) should be initialized as 0x00 on startup however we have observed that on some chips this is not the case and one or more bits in this register may be initialized as a 1.
A suitable workaround for this issue appears to be to write the default values to the register via I2C at startup.
There is also a documentation issue in the datasheet:
"The Polarity Inversion register (register 2) allows polarity inversion of pins defined as inputs by the Configuration
register. If a bit in this register is set (written with 1), the corresponding port pin polarity is inverted. If a bit in this
register is cleared (written with a 0), the corresponding port pin original polarity is retained."
In practice, the polarity inversion applies to the entire Input register and is not affected by the whether the bit is set as an output or input in the configuration register.
We have been using this part in our design for ~10 years, but have only recently received field reports and reproduced this issue in our lab. Here are the markings of a sample that has exhibited the issue: PD534 TI 13K AN89.
If you have any questions please let us know and we're happy to answer if we can.
-Garrett