TCA9517: To know the max Low-level output current

Hi Eric,

The Input and Output clamp current is the maximum current that the voltage protection circuitry can pass before experiencing damage. When voltage beyond the maximum specified value is applied to protected pins, the protection circuitry will engage by sinking current and clamp the voltage below a damaging condition. If this current exceeds the specified clamp current, the protection circuitry may fail and cause permanent damage to the device. 

The low-level output current is the recommended current through the driving pins (SDAn and SCLn) to achieve the specified low-level output voltage. If greater current flows through the driving pins, a larger voltage drop across the driver will cause the output voltage to be higher. 

Because the current through the pull-up resistor can be greater than this value, it should not be used to determine the power rating. I would recommend valuing this resistor to at least tolerate the power needed when it's connected directly from Vcc to GND (Vcc^2 / R). 
If you're asking about what value the pull-up resistor needs to be to achieve the correct output voltages, please the linked application report for equations, figures, and explanations.
I2C Bus Pullup Resistor Calculation 

Let me know if you have any more questions.

Regards,
Eric Schott