Its minimum breakdown voltage of 12.35V ensures the device starts conducting before the protected circuitry sees damaging overvoltage. Bidirectional, single-channel construction means it guards a signal pair or a single-ended line against both positive and negative surges without needing two diodes back-to-back. The SQ-MELF (B) package is a hermetic ceramic body — no moisture absorption, no popcorn cracking during reflow.
Peak pulse power and clamping — the numbers that matter
At that pulse the maximum clamping voltage is 18.2V at a peak pulse current of 27.5A. For a 9.9V rail that leaves 8.3V of headroom above the standoff — enough to absorb most transients without exceeding the downstream IC's absolute maximum. The 175°C ceiling is 25°C higher than standard TVS diodes — important when the device sits near a hot power supply or in an engine bay.
Active lifecycle — no end-of-life worry
Microchip lists the 1N6109AUS/TR as Active.