In order to avoid short-circuiting the supply voltage side to ground, also called shoot-through, for a brief moment when toggling a PWM signal from driving one motor driver to another, the drivers should be held in an inactive state for a number of PWM cycles. This is called dead-time insertion.
Since a BLDC motor controller typically uses a Hall sensor signal to determine which of the stator coils to power, this signal may also be used to trigger the insertion of a dead-time period.