Automotive Semiconductors and Functional Safety
Why are latch-up tests on automotive ICs required not only at room temperature but also at the product's maximum operating temperature?
- ABecause parasitic transistors become less active at higher temperatures, making latch-up less likely, so the test can be run under conditions that are easier to pass
- BBecause at higher temperatures the current gain of the parasitic transistors and the well resistance increase, making latch-up more likely
- CBecause ESD protection circuits stop working at high temperature, so the ESD test can be completed at the same time
Show answer and explanation
Answer: B. Because at higher temperatures the current gain of the parasitic transistors and the well resistance increase, making latch-up more likely
CMOS latch-up is a phenomenon in which parasitic pnp and npn transistors conduct as a thyristor and a large current keeps flowing. As temperature rises, the current gain of the parasitic transistors increases and the well and substrate resistance also increases, so even a small current can trigger conduction. Therefore, tests that inject current into pins or apply overvoltage are also performed at the most severe condition, the maximum operating temperature. High temperature is not used to relax the conditions, and the test is performed separately from ESD tests.
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