Protection envelope and board-fit
The 1.5SMC20AT3G: A single unidirectional channel with a 17.1V reverse standoff voltage means it begins conducting above that DC level, clamping transients on signal or DC power rails that stay below 17.1V in normal operation.
Sourcing an obsolete part
Sourcing runs through independent distribution channels: sealed reels with consistent date-codes are available against an RFQ, with the lot condition and date-code spread confirmed at quote time.
