TCA9535: TCA9535 unused pin termination

Hi Kai,

Happy to help with your questions. Thank you for the organized format!

[Question 1]
when we tied unused pins to Vcc or GND directly, are there any concern?

[A1] Electrically this is fine as long as the pins are configured as inputs. The concern is that if the tied pins were inadvertently configured as outputs, this could cause damage to the device. For this reason we recommend that biasing is done through a current limiting resistor. 

[Question 2]
regarding abso max spec, Iol continuous output low current is 50mA so we have to follow this current level.
question here is TCA9535 Icc continuous current through GND is -250mA so does it mean total Iols + leak current must be less than 250mA?

[A2] This is not the most straightforward specification. The note at the end of page 5 might clarify here:

[Question 3]
is it ok to tie every unused pins with single pull up resistor?

[A3] This is a fine method of limiting current to provide protection to multiple unused pin. This layout would still allow for device damage if the unused I/Os were inadvertently configured as outputs and driven to different levels, but the likelihood of such a configuration error may turn out to be less than the benefits of a reduced BOM. 

Let me know if you have other question or if you'd like any elaboration on the information above.

Regards,
Eric Schott