Mosfet Gate Resistance Calculation

[tomz0840]

Can anyone tell me how to calculate the gate resistor for a mosfet which is connected to a mosfet driver? For context I’m using a DRV8300 (DRV8300DPWR Texas Instruments | Integrated Circuits (ICs) | DigiKey) which is powering 6 of these mosfets (CSD18511KTTT Texas Instruments | Discrete Semiconductor Products | DigiKey).

I intend to power the mosfet driver with 12V and the DRV8300 has a typical sink current of 750mA. So the minimum resistance would be 12V/0.750A = 16Ω. We also need to account for the resistance of the mosfet gate itself (typ 0.9Ω), the traces lengths (approx 12-16uOhms per mm for me), and the source gate resistance of the driver (could not find on datasheet, only could find the bootstrap resistance).

Problem with this calculation, is that I am not sure how to optimize it based on the capacitance of the mosfet (shown below) and the switching speed (for me it is around 30kHz).

I’ve looked on YouTube and other forums but I never seem to get a clear and concise answer. Thank you for your help.

[rick_1976]

Artificially increasing the impedance of a gate drive circuit is generally undesirable. A few reasons one might consider doing so are A) because parasitic inductance in the circuit is forming an underdamped RLC circuit with the FET’s gate capacitance, or B) slower switching times are desired for some reason, such as EMI mitigation.

It’s not uncommon to see the use of a series gate resistance suggested with little explanation given as to why. I suspect that a common reason for that is because people are simply repeating things they’ve seen elsewhere without taking the time to understand them first.

Generally speaking, manufacturers’ application notes are a person’s best resource for information on electronics design topics; they’re written for the specific purpose of helping folks successfully use the products in question, by folks whose livelihood depends on that success.