An Output Buffer for 3.3-V Applications in a 0.13-μm 1/2.5-V CMOS Process

With a 3.3-V interface, such as PCI-X application, high-voltage overstress on the gate oxide is a serious reliability problem in designing I/O circuits by using only 1/2.5-V low-voltage devices in a 0.13-mum CMOS process. Thus, a new output buffer realized with low-voltage (1- and 2.5-V) devices to drive high-voltage signals for 3.3-V applications is proposed in this paper. The proposed output buffer has been fabricated in a 0.13-mum 1/2.5-V 1P8M CMOS process with Cu interconnects. The experimental results have confirmed that the proposed output buffer can be successfully operated at 133 MHz without suffering high-voltage gate-oxide overstress in the 3.3-V interface. In addition, a new level converter that is realized with only 1- and 2.5-V devices that can convert 0/1-V voltage swing to 1/3.3-V voltage swing is also presented in this paper. The experimental results have also confirmed that the proposed level converter can be operated correctly