DRV8889-Q1: How to set the ITRIP current

hi :

         We use a bipolar stepper motor with a coil impedance of 220 ohms per phase and a working voltage range of 9 to 18 V, which means that the minimum current across the coil is 9/220=40.9 mA; The maximum current through the coil is 18/220=81.8mA. If the motor uses 1/2 step, what should be paid attention to when setting the Itrip current? Is the Itrip current required to be less than 40.9 mA for each step in a 1/2 step?