What the 1.5SMC68C is and what it protects
The 1.5SMC68C is a unidirectional bidirectional TVS Zener in the Littelfuse 1.5SMC series, packaged as a DO-214AB (SMCJ pinout) for surface-mount assembly.
TVS selection ceiling — what the numbers govern
Standoff voltage (58.1 V typ) is the dc rail the protected node runs at continuously; the TVS must sit above this with margin or it leaks above spec. Breakdown (61.2 V min) is where conduction begins — the device is not a linear regulator, it snaps into conduction above that threshold. Clamping voltage (96.6 V max at 16.5 A peak) is the worst-case voltage across the TVS pins at rated surge current, and is the number the downstream IC or MOSFET gate oxide sees when the event fires. Bidirectional — one active Zener in each direction — so it clamps both positive and negative transients without polarity concern on the board. Power line protection is listed No: this part is not a pass-through bus protector, it is a shunt clamp across the node it guards.
Obsolete lifecycle — sourcing reality
Littelfuse has marked the 1.5SMC68C obsolete. No authorized-stock carry is implied, and the Tape & Reel packaging means any lot found through independent channels is date-code-sensitive — verify the MSL rating before reflow if the lot is aged.