A reliable and high voltage compatible CMOS I/O buffer

A high voltage tolerant and reliable CMOS I/O buffer without using thick-oxide devices is presented. By the floating n-well technique, the proposed design has a simpler structure and the good gate-oxide reliability is achieved. In addition, it is dc leakage free and has no redundant pad for dual powers. From the simulation results, the proposed circuit can demonstrate both speed enhancement about 20% in pull-up operation and 50% saving in area. Therefore, the proposed I/O buffer is very suitable for mixed voltage interface applications.