A latch-up occurs when parasitic bipolar transistors within a CMOS chip accidentally turn on, creating a low-impedance path directly between the power supply and ground. Once triggered by a voltage spike or ionizing radiation, this parasitic thyristor stays locked on until the power is removed. If the power supply can deliver enough current, the resulting heat will quickly melt the silicon and permanently destroy the chip.
The inductive kickback caused a latch-up, and the microcontroller let out the magic smoke before the fuse could blow.
To prevent latch-up in sensitive designs, engineers use guard rings around vulnerable transistors or build the chip on an insulating substrate.
Related terms
CMOS
Complementary metal-oxide-semiconductor is the dominant fabrication technology for integrated circuits.
Parasitic element
An unintended component characteristic, such as stray capacitance or lead inductance, that affects circuit operation.
Thyristor
A four-layer semiconductor device that acts as a bistable switch for high-power applications.
MOSFET
A metal-oxide-semiconductor field-effect transistor is a voltage-controlled switch used to amplify or switch electronic signals.