FYI, you can calculate the RLC parameters of the drive circuit, and do a simple sanity check on whether it's reasonable or not, and to see what minimum Rg you need.

For inductance, assuming the path has a transmission line impedance in the 50-150 ohm range (less if you use lots of wide traces and parallel pins), then since that's about half of Zo (377 ohms), inductivity is about half of mu_0, or ~0.6 uH/m.

That's inductance per linear length of path. So, say 3 inches (0.075m), 45nH. More or less.

Gate capacitance. You need the total equivalent, not the zero-bias figure. That parameter low-balls the equivalent by around 4x. Take Qg / Vg(on) = Cg(eq). Qg is Qg(tot), preferably the max spec. Vg(on) is the value Qg is measured at.

Suppose Qg is 50nC at 10V. That gives Cg(eq) = 5nF.

Impedance. This is nothing more than sqrt(L/C) = Z. The ratio of inductance to capacitance, works precisely the same as the ratio of voltage to current (I mean, give or take a square or root), and has units of ohms.

If Lstray = 45nH and Cg = 5nF, then 45/5 = 9, and sqrt(9) is 3. So, 3 ohms.

Pick Rg > Z. Equal gives critical damping; over gives extra damping (~RC characteristic).

Note you also want Rg on the order of the driver's output capacity, i.e., R ~ (VCC / Ipk). Like for the SG3525 (0.5A peak max.) at 12V, you'd use around 6 ohms. (Less than 3 ohms won't really do anything -- the driving pin will be driving the gate nearly directly at that point. More will significantly reduce the load on the driver, which slows things down. Slow may be desirable for EMI.)

In either case, pick the greater of the two options.

Naturally, L and C also define a characteristic time constant, or cutoff frequency. The frequency is F = 1 / (2*pi*sqrt(L*C)), and the time (1/4 wave) is t = pi*sqrt(L*C)/2.

For this example, the time is 23ns. Against a typical 50ns fall time of the SG3525, you won't have to worry about Lstray or Rg this low.

If the risetime of your driver is already slower than the 1/4 wave time, then choosing Rg ~= Z will have little to no effect on actual speed. If you want to slow it down further, you'll need to use that many times more Rg to have an impact.

I'm guessing something around 10-50 ohms would be best, or if you want to go for speed, use the local-driver design, and whatever Rg is suitable then (maybe 1-10 ohms).

Tim

Edit: helps if I use consistent numbers