I am trying to understand how to select an appropriate MOSFET driver for controlling a DC motor. I went through quite a lot of literature from Texas Instruments and Microchip, but I am still not able to completely understand how to exactly calculate the gate driver current. Microchip has an application note on how to calculate the gate drive current which notes that the gate drive current (I_G) = Q_G/t, where Q_G is the total gate charge and t is the rise time.
While looking at some drivers on the TI website, I found the DRV8701 and the corresponding EVM module. Going through the schematic the GH and GL pins are connected through a 0 Ohm resistor to the gate of the transistors CSD18532Q5B. The maximum series gate resistance of MOSFET is 2.4 Ohm. According to the DRV8701 datasheet, I_DRIVE is 6 mA when the R_IDRIVE is <1KOhm to the ground ( I am assuming this the R_IDRIVE I should be looking at ). When I do the math for required Gate current as per the Microchip Application note, it comes out to be 8.05 A (=58 nC/7.2 ns). Even if I look at the maximum I_DRIVE current of the DRV8701 (150 mA), this requirement will not be satisfied.
I am not sure what I am doing wrong. When I use a PWM signal does the I_G value reduce depending on the duty cycle? Is this why the 8701EVM is capable of driving the said FET