500 W peak pulse in a SQ-MELF — what it handles
That 500 W rating means it can absorb a 5.1 A surge without letting the voltage climb past 97.1 V — useful for clamping transients on a 51.7 V rail. The reverse standoff voltage is 51.7 V typ, with breakdown guaranteed between 64.6 V min. If your rail sits at 48 V or 52 V nominal, this part gives you a guard band before the TVS starts conducting leakage current.
The SQ-MELF (B) package is a ceramic-like surface-mount body that handles thermal cycling better than a plastic SMC.
That means you can BOM it without planning a last-time-buy or a qualification cycle for a replacement. The base product number is 1N6126, so if you see other suffix variants (e.g., leaded or different screening levels), the core die and breakdown voltage are the same — only the package or test flow changes.