Circuit with hot electron protection and method

摘要

An I/O circuit whose output receives a voltage VPAD which is temporarily higher than a critical voltage VDS MAX>VDS 1 across drain and source of a conducting first N-FET (110, N1) acting as a pull-down device. The first N-FET is protected against hotelectron induced degradation by a serially coupled second N-FET (130, N3). A variable drain-source voltage VDS 3 is added to VDS 1. A comparator (150) compares the received voltage VPAD to a supply voltage VCC and pulls a gate (G) of the second N-FET (N3) to VPAD or to VCC. The conductivity of the second N-FET (N3) is thereby changed so that VPAD is distributed among VDS 1 and VDS 2. The comparator (150) conveniently comprises two P-FETs (P1, P2, 160, 170).