H-Bridge Sensing Voltage
The figure -1 to 2.3V is an absolute limit and ideally it will be slightly positive (maybe 0.25V under load) if you are using sense resistors.

The sense pins on the device are when you need to connect a small value resistor to "check" the current drawn by the load on the H bridge. If you are not using these pins connect them to ground or the H bridge won't work. This ground connection takes the main load current so do it properly or you'll get problems.