PCA9548A: whether the unused channel can be NC

Hi Frank,

Because PCA9548A uses pass-FET based enables for each channel, unused pins should not be left floating. We generally recommend tying unused ports to Vcc through weak pull-ups (~100k). This provides a stable state in case the channel is inadvertently enabled.  This is not necessary for device functionality however, and the pins may be tied to Vcc when trying to save PCB components - however this would may have adverse effects (device damage) if the channel is accidentally enabled. Using a single large resistor to commonly pull up all unused lines is another way to reduce BOM cost while avoiding a potentially hazardous scenario - though accidental enables may still cause lockup.

Let me know if you have any other questions about how these unused channels can be handled. 

Regards,
Eric