Design on power-rail ESD clamp circuit for 3.3-V I/O interface by using only 1-V/2.5-V low-voltage devices in a 130-nm CMOS process

A new power-rail ESD clamp circuit in a 130-nm 1-V/2.5-V CMOS process for application in a 3.3-V mixed-voltage I/O interface is proposed. The devices used in this power-rail ESD clamp circuit are all 1-V or 2.5-V low-voltage nMOS/pMOS devices, which are specially designed without suffering the gate-oxide reliability issue under 3.3-V I/O interface applications. A special ESD detection circuit realized with the low-voltage devices is designed to improve ESD robustness of the stacked nMOS by a substrate-triggered technique. Experimental results, verified in a 130-nm CMOS process, have proven the excellent effectiveness of this new proposed power-rail ESD clamp circuit.