9.1 Application Information

High-current gate driver devices are required in switching power applications for a variety of reasons. To enable fast switching of power devices and reduce associated switching power losses, a powerful gate driver can be employed between the PWM output of controllers or signal isolation devices and the gates of the power semiconductor devices. Further, gate drivers are indispensable when sometimes it is just not feasible to have the PWM controller directly drive the gates of the switching devices. The situation will be often encountered because the PWM signal from a digital controller or signal isolation device is often a 3.3-V or 5-V logic signal which is not capable of effectively turning on a power switch. A level-shifting circuitry is needed to boost the logic-level signal to the gate-drive voltage in order to fully turn on the power device and minimize conduction losses. Traditional buffer drive circuits based on NPN/PNP bipolar, (or P- N-channel MOSFET), transistors in totem-pole arrangement, being emitter follower configurations, prove inadequate for this because they lack level-shifting capability and low-drive voltage protection. Gate drivers effectively combine both the level-shifting, buffer drive and UVLO functions. Gate drivers also find other needs such as minimizing the effect of 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.

The UCC2753x is very flexible in this role with a strong current drive capability and wide supply voltage range up to 32 V. This allows the driver to be used in 12-V Si MOSFET applications, 20-V and -5-V (relative to Source) SiC FET applications, 15-V and -15-V (relative to Emitter) IGBT applications and many others. As a single-channel driver, the UCC2753x can be used as a low-side or high-side driver. To use as a low-side driver, the switch ground is usually the system ground so it can be connected directly to the gate driver. To use as a high-side driver with a floating return node however, signal isolation is needed from the controller as well as an isolated bias to the UCC2753x. Alternatively, in a high-side drive configuration the UCC2753x can be tied directly to the controller signal and biased with a nonisolated supply. However, in this configuration the outputs of the UCC2753x must drive a pulse transformer which then drives the power-switch to work properly with the floating source and emitter of the power switch. Further, having the ability to control turn-on and turn-off speeds independently with both the OUTH and OUTL pins ensures optimum efficiency while maintaining system reliability. These requirements coupled with the need for low propagation delays and availability in compact, low-inductance packages with good thermal capability makes gate driver devices such as the UCC2753x extremely important components in switching power combining benefits of high-performance, low cost, component count and board space reduction and simplified system design.