What this TVS diode protects and where it fits
It clamps transients at 245.7V maximum when the surge current reaches 6.1A, with a reverse standoff voltage of 136.8V — meaning it stays out of the way below that DC level and only conducts during an overvoltage event. The SQ-MELF C package is a surface-mount ceramic barrel with C-bend leads, designed for automated pick-and-place and reflow soldering. The ceramic body handles the thermal shock of a 1500W pulse without cracking, which is why you see this package in military, avionics, and downhole applications where board space is tight and reliability is non-negotiable.
Breakdown, clamping, and temperature — the numbers that matter
Minimum breakdown voltage is 171V, so the diode starts conducting somewhere above that threshold. The clamping voltage of 245.7V at 6.1A peak pulse current tells you the maximum voltage the protected circuit will see during a surge — design your downstream components to survive that ceiling. The 1500W rating is derated at elevated temperatures; the datasheet derating curve (not reproduced here) is the reference for your thermal budget.
Active production — sourcing without last-time-buy pressure
The base product number is 1N6172; the 'AUS' suffix denotes the SQ-MELF C package variant. If you have a 1N6172 in a different package, confirm the mechanical fit before substituting — the electrical specs are identical, but the footprint and solder profile differ.