“…In known approaches to wear-out monitoring [9], [10], [16], [11], [12], [13], [14], some consider electromigration [9], some consider NBTI (Negative Bias Temperature Instability) [11], [12], [14], some gate oxide breakdown [9], [13] or some other or unspecified wear-out mechanism [16], [17]. Several of the known wear-out mechanisms have in common that they affect the signal propagation delay through a circuit.…”