A single-event latchup is a radiation-induced failure in which a transistor allows excessivve current to flow, potentially damaging connected components.

A Single-event latch-up occurs when a high-energy particle strikes a transistor with enough energy to open a parasitic current path. This allows current to flow unimpeded through the transistor, potentially allowing current flow that it orders-of-magnitude higher than the design limits. In extreme cases this current can create permanent damage to downstream electronics.

When the device is power-cycled, the parasitic path is closed, and the device can operate normally again.

Single-event latch-ups are potentially the most destructive form of single-event effect. They are mitigated by using a latching current limiter on output lines.