A new design of mixed-voltage I/O buffers with low-voltage-thin-oxide CMOS process

A novel circuit of mixed-voltage I/O buffer is proposed in this work. The new buffer uses NMOS driver transistors instead of PMOS-driver, which is commonly used in the prior designs. With the help of a bootstrapped circuit, the buffer is free of the threshold voltage loss problem originated from NMOS driver. The proposed buffer can overcome the problem of leakage current paths and gate-oxide reliability issue. Simulation results show that the new buffer operates successfully when used in 1.8 V/3.3 V I/O interface.