Can I left the pin unconnected??

The LXT971 has the /MDINT pin, in the evaluation board, this pin is connected to the CPLD,and there are no other pin connected to it. I havn’t CPLD,Can I left the pin unconnected??

You can’t leave a ping floating noise or such thing may affect and the result would be unpredictable so you need to disable it by pulling it high.

Empty post’s body.

I have to disagree. This signal is an output from LXT971A and is normally high impedance (open drain output). If you do not want to use this signal you will never enable any external interrupts in the LXT971A and the signal will always be high impedance. I see no reason to connect a pullup on this signal. Many designs have unconnected outputs, for example, the RS232 drivers on the development board has several unconnected outputs.