A latchup is the inadvertent creation of a low-impedance path between the power supply rails of an electronic component, triggering a parasitic device, which then acts as a short circuit, leading to ceasement of proper function of the part and perhaps even its destruction with the overcurrent. A power cycle is required to correct the situation.
The device that is in latchup has ceased to function and is vertualy in a locked state
Can be caused by many things, ie noise on a power line , poor bising of the device , input output conditions incorrect .