What this TVS protects and where it lived
The 1.5KE22AHE3/51 is a 1500 W peak-pulse-power TransZorb® TVS diode from Vishay, part of the automotive-grade AEC-Q101 series. It clamps transients at 30.6 V max when hit with a 49 A 10/1000 µs pulse, and its 18.8 V reverse standoff means it sits across a 12 V or 15 V rail without leaking until a surge arrives. The DO-201AA axial-lead package is a through-hole workhorse — the same footprint as a 1N5400 rectifier, so it drops into existing board layouts without a pad spin.
Why the obsolete status matters for your BOM
If you are repairing an automotive ECU or a power supply that originally used this TVS, the 1.5KE22AHE3/51 is still findable on the spot market. For a new design, look at Vishay's current 1.5KE series (non-automotive) or the automotive-grade SAxxA family — but confirm the clamping voltage and package match before swapping.
Clamping numbers that decide fit
The breakdown voltage range starts at 20.9 V min — that is the point where the diode begins conducting. The clamping ceiling is 30.6 V at the rated 49 A pulse, so the protected rail must survive a 30.6 V transient without damaging downstream silicon. Power line protection is marked No — this is a unidirectional TVS for DC rails, not for AC mains. The single-channel unidirectional construction means it clamps only one polarity; reverse-voltage protection requires an additional series diode or a bidirectional part.