The interlocking feature is a little bit different. This slide shows the truth table of the L6390. If LIN and HIN enables both gates at the same time, a short circuit occurs between the DC bus and ground. To avoid this short circuit, the interlocking feature turns OFF the gate drivers when the application tries to turn the gates ON at the same time. In some power supply applications, both gates must be turned ON at the same time, so this function is not always integrated.