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SLUSAY4C – MARCH 2012–REVISED MAY 2013
TYPICAL CHARACTERISTICS (continued)
RISE TIME FALL TIME
vs vs
SUPPLY VOLTAGE SUPPLY VOLTAGE
Figure 17. Figure 18.
APPLICATION INFORMATION
Introduction
High-current gate-driver devices are required in switching power applications for a variety of reasons. In order to
effect fast switching of power devices and reduce associated switching power losses, a powerful gate driver is
employed between the PWM output of controllers and the gates of the power-semiconductor devices. Further,
gate drivers are indispensable when there are times that the PWM controller cannot directly drive the gates of
the switching devices. With advent of digital power, this situation is often encountered since the PWM signal from
the digital controller is often a 3.3-V logic signal, which is not capable of effectively turning on a power switch. A
level-shifting circuitry is needed to boost the 3.3-V signal to the gate-drive voltage (such as 12 V) in order to fully
turn on the power device and minimize conduction losses. Because traditional buffer-drive circuits based on
NPN/PNP bipolar transistors in totem-pole arrangement, being emitter-follower configurations, lack level-shifting
capability, the circuits prove inadequate with digital power. Gate drivers effectively combine both the level-shifting
and buffer-drive functions. Gate drivers also find other needs such as minimizing the effect of high-frequency
switching noise by locating the high-current driver physically close to the power switch, driving gate-drive
transformers and controlling floating power-device gates, reducing power dissipation and thermal stress in
controllers by moving gate-charge power losses into itself. Finally, emerging wide-bandgap power-device
technologies, such as GaN based switches, which are capable of supporting very high switching frequency
operation, are driving very special requirements in terms of gate-drive capability. These requirements include
operation at low VDD voltages (5 V or lower), low propagation delays and availability in compact, low-inductance
packages with good thermal capability. In summary gate-driver devices are extremely important components in
switching power combining benefits of high-performance, low cost, component count and board space reduction
with a simplified system design.
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