They bring up a good point that adding Cgs alone may cause more harm than good. If they also increase dead time then the added Cgs will have the intended effect.
Thanks, as you know, the majority of synch buck controllers offer no facility to vary the dead times. And usually, the dead time is horrendously small...usually 15 to 40ns, so indeed, adding the external Cgs capacitor would usually not be a good fix.
Indeed, it is amazing that the dead times are made so ridiculously short...since most people will have a logic level "freewheel" fet in the synch buck...and they will implement its drive with a series "ON" resistor, and a diode'd "OFF" resistor.....but since a hot logic level fet can be fully enhanced with just 0.5v on its gate...the "diode turn off" circuit will not work very well...and so indeed, the lower "freewheel" fet is likely to be ON when the top fet turns on.......smoke or overheating resulting.......so the whole thing is a bit of a shambles.
I bet that most synch bucks that are out there, with vin > 24V, would truthfully be more efficient if they simply threw away the lower "freewheeling fet" and put in a low voltage Schottky instead.
Also, its noteable that Qgd/Qgs must be <1, though during spurious turn on in sync bucks, the lower FET actually has its gate shorted to ground by the driver, (and via any series resistance which would be low value)....so in fact, it makes you wonder why "Qgd/Qgs < 1" really applies in real life?
Another point, is that if you are using Normal threshold (not logic level) fet drive, and have a PNP turn off snubber right on the fet gate, then its going to be virtually impossible to get the shoot-through condition due to Qgd/Qgs>1.
However, this is not the case with logic level fets, since the PNP turn off wouldnt be of much use with the gate threshold being so low...the PNP woudlnt be able to turn on enough and in time.