Can I use USBLC6-2SC6 to protect 3.3V bus and lines?
Read this first: -

So, you can inject current into an input or an output providing that you do not exceed 25 mA. If your input bus line is protected by a TVS diode then, between TVS diode and the actual input pin you place a resistor: -



simulate this circuit &ndash; Schematic created using CircuitLab
The TVS has to clamp to no more than 13.8 volts to ensure that no more than 10 mA will flow into the pin.
So, choose how much current you want to allow into the pin under ESD events and insert a resistor between pin and TVS then, do the ohm's law math.