INA381: Unused pin.

Hello Kengo,

Thanks for considering to use Texas Instruments.  According to the datasheet the preferred connection is pulled-up to supply with a 10kΩ.  However, the datasheet does mention that the comparator has an open drain output.  Therefore, shorting the ALERT pin to gnd should be fine as a mosfet typically has high impedance from gate to drain and gate to source. If the gate to the comparator's output is triggered, you would just have a short from the drain to the source, which would both be at the ground potential.

As you are not using the comparator, I think it might be worthwhile choosing another part as that feature does add some cost.  I checked our parametric table here and saw that we have several parts with similar specs excluding the comparator that cost less.