How to determine whether I need ESD protection? (MOSFET H-Bridge)
The MOSFETs aren't sensitive to ESD on the source and drain. If you zap the bridge output the transistors will take the hit: the drain to source capacitance will limit the transient rise time, and they are rated for an avalanche breakdown energy of several hundred millijoules at room temperature. The gate of the transistors is susceptible to ESD but it isn't an exposed connection. I would be more worried about the optocoupler LEDs being zapped, but even they are fairly rugged. If the power supply input is zapped the input filtering caps will bypass most of the pulse.