The purpose of this circuit is to restrict the output current to less than 20mA, and this limit can be adjusted using resistors R1 and R8. Furthermore, the circuit also can disconnect the input/output when the output short circuits to a high positive or negative voltage by limiting the current.
Additionally, the diode D1, located at the output and the 5V0 pin, serves to suppress the kick-back voltage from an inductive load. This occurs when the drivers are deactivated (stop sinking) and the stored energy in the coils causes a reverse current to flow into the coil supply through the kick-back diode.
