SLVAF66 June 2021 DRV3255-Q1 , DRV8300 , DRV8301 , DRV8302 , DRV8303 , DRV8304 , DRV8305 , DRV8305-Q1 , DRV8306 , DRV8307 , DRV8308 , DRV8320 , DRV8320R , DRV8323 , DRV8323R , DRV8340-Q1 , DRV8343-Q1 , DRV8350 , DRV8350F , DRV8350R , DRV8353 , DRV8353F , DRV8353R
In most gate driver devices, the source and sink, or pullup and pulldown, gate-drive current values are found in the data sheet. In some devices, this value is fixed internally, and the output current capability is much larger than the calculated IDRIVE for a given FET.
Add an external series gate resistor to control the slew rate of the applied gate voltage and reduce the peak current applied to the gate of the FET. This is similar to a RC filter: R is the gate resistor, and C is the inherent capacitance of the MOSFET. For further control, place another gate resistor and diode in parallel – if the designer wants to control sink and source separately. This is shown in Figure 3-2.
The MOSFET parameters, system voltage, and board parasitics all affect the final slew rate, so selecting an optimal gate resistor value is an iterative process. This process is explained in the External Gate Resistor Design Guide for Gate Drivers tech note.
There is a helpful principle that is beneficial to help determine the best resistance to use for a gate resistor: less resistance equals more current with a faster slew rate, and more resistance equals less current with a slower slew rate.