You could post your schematic for more info , gate resistors play a role in the speed of turn on/off (not only the current supplied by the totem pole).
I have worked with power mosfetsMOSFETs in halfbridgehalf-bridge and full bridge topologies and one most of the causes for failure seems to be voltage spikes.TVS TVS diodes across lower side switch can help.But But the real solution is to rely on the Avalanche ratingavalanche rating of the mosfetMOSFET and overrate mosfetMOSFET voltage (VDS\$V_{DS}\$). So for 24v24 V system , use 75v mosfet 75 V MOSFET, for 36v36 V system use 100v mosfet100 V MOSFET and for 48v48 V system use 150v mosfet150 V MOSFET.
Current rate your mosfetsMOSFETs properly for steady state and overcurrent condition , use a number of mosfetsMOSFETs that can handle safely (thermal limit) handle the continuous rating of the motor and the spikes are manged by mosfetsMOSFETs themselves because the can handle overcurrent easily , You donotdo not need 16 mosfet MOSFETs, for example
This infineon mosfetInfineon MOSFET is rating 7.5mohm5 mOhm at 150v150 V in to220TO220 package . So for 200a200 A 8 of these in parallel should work if heatsinked properly. Power loss in each transistor is (200/8)x(200/8)x7.5= 4.6w6 W which is realistic.
andAnd pushing 25a25 A per transistor is well under max wirebond limit , which leaves space for current spikes.
Adding a current sensor , hall effect or a 1 milli ohmOhm shunt with current sense amplifier should work in limiting acceleration deceleration , and preventing over current condition if you sample current and control PWM fast enough (cycle by cycle current limit)
On of the most important factors is the layout of you power and gate drive circuit since you are switching high current at few kilohertz, any stray inductance in the circuit will create huge voltage spikes , especially at mosfetMOSFET gate and source. forFor 16 mosfet iMOSFET I can imagine the length of the gate driver trace or wire ! lookLook for some app notes regarding minimizing gate drive ringing an-937 and APT0402.
After seeing your schematic :
I recommend :
1- I WILL STRESSTRESS More on overrating mosfetMOSFET voltage rating and I will backup my answer by automotive standards which use 40v40 V transistors in 12v12 V car systems , and 75v75 V for 24v24 V trucks electrical systems . I think the reason is load dump and such spikes . thisThis will prove important in field testing in harsh enviromentsenvironments not on your test bench .
So the least you can do is using IRFP4468PBF mosfetMOSFET (100v100 V rated not 75v75 V or 60v60 V like the ?IRFB7730?) remember 48v. Remember 48 V system is not actually 48v 48 V, because batteries fully charged whether lithium or lead acid is around 55 to 60v60 V so you need to keep some margin.
2- Add gate resistors around 3-5ohm5 Ohm for each transistor (they wont slow down the turn On turn on) remember 15/3=5A3=5 A per transistor which can charge the gate of Qg=500nCQg=500 nC in : dt=q/I= 100ns100 ns which is more than enough for 20khz20 kHz switching frequency.
3-fast fast turn off circuit is not needed , just use a schottkySchottky diode anti parallel to gate resistor , since the TC4422 will turn off the mosfetMOSFET quickly.
4-USE USE BETTER HEATINK HEATSINK, iI cannot beleaivebelieve that you are pushing that amount of current from mosfetMOSFET and just using that tiny peicepiece of metal to remove heat, especially if the board is working for sometime themsome time then failing , that means the failure is due to overheat. ifIf you have thermal imager that would be great in detecting such the heat stress concentration . attachAttach the mosfetsMOSFETs to aluminum of copper thick bars and use fans if necessary something used in welding machine
byBy the way there are posts on this websites that would tell you how to calculated thermal resistance and how much heat will build up from the transistor at the specified power loss.
5- sorry for mistake on current sensor i, I meant the shunt should be 100micro ohmOhm (not 1milli). Better is to use contact less isolated hall sensor around the wire like these.
Remember Bi-directional current sensors are very important in motor drive because you can attach them to motor wire (not before ground) to sense current supply and regenerative current during braking so you can limit both currents.
