In applications using a gate driver with independent high-side and low-side input controls, dead time is typically added to the driver input signals to prevent cross-conduction, or shoot-through, between the output transistors. This cross-conduction protection is important as a shoot-through event can cause excess current draw or even damage the output transistors and PCB.

Input interlock is a feature of gate drivers such as LM5108 that turns off the high-side and low-side outputs if the two input signals are simultaneously high. This function filters out any shoot-through conditions on the input such as noise. As input interlock only controls input overlap and cannot account for rise time and fall time on the output pins, dead time still needs to be added to the input signals to compensate for output switching speed. For example, if the high-side and low-side input signals are exactly opposing each other with no dead time, there can be a shoot-through condition during the duration of the output rise time and fall time. An exception to this is LM5104 which uses an adaptive delay system on the output to prevent the outputs from overlapping during rise and fall times by inserting additional adaptive output dead time.

Gate drivers with fixed internal dead time insert a short, fixed time period between the falling edge of one output and the rising edge of the other output. This provides basic shoot-through protection without an additional external set resistor. LM2103 and LM2104 provide 475ns typical fixed dead time.

Adjustable or programmable dead time is a feature of some gate drivers that is usually set by connecting a resistor to a dedicated dead time adjustment pin. Compared to fixed dead time, adjustable timing allows for greater flexibility to minimize deadtime for optimized efficiency while still preventing shoot-through. In a motor drive application, programmable dead time allows for improved control of switching transitions between power devices leading to benefits such as reduced switching losses, improved output transients, and the ability to adapt to different motor and operating conditions. The dead time on LM5104 can be set with a resistor value between 10kΩ and 100kΩ, resulting in an effective dead time proportional to the set resistance and ranging from 90ns to 200ns as shown in Figure 2-4. The dead time for LM5105, and LM5106 can also be set with a resistor value between 10kΩ and 100kΩ to set a delay from 86ns to 510ns as seen in Figure 2-5 showing the timing range from 10kΩ to 150kΩ.

A gate driver with adjustable or fixed dead time and interlock control can streamline the microcontroller timing logic by removing the requirement for the microcontroller to maintain safe dead time periods between multiple PWM output signals. The adjustable dead time feature also allows for easy timing changes by simply changing the dead time set resistor without the need to modify the microcontroller programming.