Active guard ring to improve latch-up immunity

A new design concept named as active guard ring and related circuit implementation to improve the latch-up immunity of ICs are proposed. Using additional sensing circuit and active buffer to turn ON the electrostatic discharge (ESD) protection transistors, the large-dimensional ESD (or I/O) devices can provide or receive extra compensation current to the negative or positive current perturbation during the latch-up current test. The new proposed solution has been verified in 0.6-μ m 5 V process to have much higher latch-up resistance compared with the conventional prevention method of guard ring in CMOS technology.