Leg Short Circuit (Shoot-Through)
The condition where the upper and lower switch in an H-bridge leg conduct at the same time. A short-circuit path that bypasses the motor opens between supply and chassis; only cable and switch resistance limit the current, which can reach hundreds of amperes. The result is usually permanent damage to the switch.
Shoot-through arises in two ways. The first is a logic fault: accepting two direction commands at the same time. The second and more insidious one is timing. A MOSFET can take longer to turn off than to turn on; if the commands are given as exact complements, the lower switch starts conducting before the upper one has fully turned off, and a current pulse shorter than a microsecond is born.
This pulse is usually too short to blow the fuse but large enough to kill the semiconductor. The damage is often not visible immediately; repeated pulses wear the switch out and after a while it ends in a permanent short circuit. A faulty board typically announces itself by blowing the fuse the moment power is applied.
The means of protection fall under three headings: putting dead time between complementary signals, interlocking the two direction commands in hardware, and applying a short wait when reversing direction. The most concrete contribution you can make in the field is the third one: instead of switching a running motor instantly into reverse, stop it first and give the reverse command after a short delay.
The context in which this term is used: DC Motor Driver Selection Guide