14.3.3 Special Cases in the circuit
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An area for potential concern is forward-biased diode. Diode under dc forward bias should be avoided as a circuit component. In case such diode has to be used, it must be marked by Latchup_MK layer and it shall be surrounded by N+/Nwell guard rings and optionally by P+ guard rings. Such rules need to be followed if significant over voltage and under voltage conditions exist in any diffusion in the core.

Floating Nwell without any injecting diffusion is generally not a latch-up concern. Reliability Group will be available to assess possibility of latch-up in special circuit cases.