Five volt tolerant protection circuit

摘要

A low voltage driver tolerant of high voltage and suitable for driving a processor (510) and a memory device (512). A first protection NFET (412) is coupled to the drains of a series-coupled PFET (322) and NFET (324) forming the basic driver components. Another protection NFET (414) is connected in series to the first NFET (412). This second protection NFET requires approximately 1 volt for turn on, such that a resultant 3 volts appear at the output of the complete driver assembly. When the output driver is not enabled and 5 volt inputs are being applied from the memory circuit, the two NFET protection transistors block the 5 volts from reaching the processor output driver.