My customer discovered that their board layout left the address pins A0 and A1 floating for the TCA9539 (WQFN package). The desired setting would be to pull these to ground to set A1/A0 to 00.
However, they have found that the devices responds correctly with board testing so far as if the pins are pulling low. My understanding is that there is no internal pull-up or pull-down on these pins.
Is there any internal circuitry that would tend to have these pins default as logic low, or is the state completely random when the pins are left floating and they are just lucky it appears to work?
