Issue link: https://resources.mouser.com/i/1505196
mouser.com/vishay / 17 A gate driver circuit is similar to a classic RLC circuit, which most engineers should be familiar with. If the resistance values are too high, switching times and power losses increase. If the resistance values are too low, the gate circuits start swinging. Some refer to the damped oscillation as ringing. Oscillation can be changed by increasing the damping or by reducing one of the system's energy stores. The parasitic capacitance of a switch is provided by the supplier, while the inductance of the driver circuit is given by the designer of the substrate or PCB used. It's always a good idea to keep the tracks of a substrate as short and close together as possible in order to avoid ringing and reduce emissions. The selection of resistance values needs to be determined by measuring the oscillation in the driver as well as in the power circuit. So, what types of resistors can be used in switches? To reduce electromagnetic compatibility (EMC) failures, the whole design of the driver circuit should consist of surface- mount components. Typical sizes range from the 0402 or 0406 case sizes to the surface-mount MELF DIN 0207. Based on the applied resistive material and the effective volume and mass, the continuous peak power range at 1µs starts at 9W for the 0402 and ends at 900W for the 0207. It should be noted that the pulse load diagrams for Vishay resistors are valid for the whole resistance range until the peak voltage sets the limitations. That means the test equipment used is not designed to drive high voltages in rise times of several ns; it's designed to drive high pulse voltages in rise times of several hundred ns. For cases that can't be covered by datasheet information, our application engineering team can help. Resistor products from Vishay cover a wide power dissipation range—from 200mW for a standard surface-mount component like the CRCW0402-HP e3 or 4W for the integrated wire bondable IGBR—for a variety of possible solutions. Due to the short rise times involved, the RF performance of a gate resistor could be considered as well. The parasitic elements in the resistance range of 1W to 100W are more heavily influenced by the parasitic inductance. As an example, a surface- mount MICRO MELF shows—depending on the number of trimming cuts—a typical value of 2.1nH to 2.4nH. Generally, the parasitic inductance of a discrete gate resistor is much lower than the inductance of the substrate. Due to the short rise times of the wideband materials, a compromise must be reached between switching losses and electromagnetic interference (EMI) performance. EMI emissions need to be reduced and the rise time of the switch needs to extended, which has the negative impact of increased switching losses and vice versa. In applications with limited space, resistors need to be placed in parallel to keep the temperature and drift low. In the event that the gate resistor is placed very close to the power switch, the heat flow out of the power switch into the substrate should be considered, because it has an impact on the stability and drift of the resistance value as well. Vishay is well recognized for its products' quality and engineering performance. Out of our wide range of products, we offer a handful of resistor series that are well-known on the market. These include the discrete CRCW-HP e3 and RCL e3 in thick film; SMM, MMx, CMx in thin and carbon film MELF; and the TNPW e3 and MCW-AT in thin film. For power electronic designs that require the gate resistor on the power module, please refer to the latest datasheet for the new IGBR series. Learn More IGBR Thin Film Resistors Learn More RCL Thick Film Chip Resistors CRCW-HP e3 Thick Film Chip Resistors Learn More