What this TVS diode does on the line
The 1.5KE9.1CAHE3_A/D: It clamps transients at 13.4V max when hit with a 112A pulse, and its 7.78V reverse standoff means it sits across a 5V or 12V rail without conducting in normal operation.
Clamping voltages and what they mean for your rail
Breakdown starts at 8.65V minimum, so a 12V battery line that sees a load-dump transient gets clipped before the downstream regulator sees more than 13.4V. The 112A peak pulse current (8.65V min breakdown to 13.4V clamp) means it can absorb a direct lightning-induced surge on an automotive harness without failing short. Bidirectional — one device handles both positive and negative transients, saving a board position compared to back-to-back unidirectional diodes. The DO-201AA axial package is through-hole, easy to hand-solder or wave-solder, and the body marking is clear enough to read orientation in a rework station.
Packaged in Tape & Box (TB), not reel — fine for through-hole assembly lines that feed axial parts from a tube or tray. No RoHS/REACH conflict noted; the TransZorb® series has been lead-free compatible for years.