Circuit for auto-clamping input pins to a definite voltage during power-up or reset

摘要

An auto-grounding circuit responsive to a reset signal discharges an input terminal of an integrated circuit and its associated input line to ground, using a pull-down transistor coupled to the input line, with a gate of the pull-down transistor coupled to receive the reset signal. An exemplary circuit also includes a NAND gate and a second pull-down transistor to maintain an established voltage level of the input line after the reset signal is no longer asserted until the input terminal is driven by an applied input signal. The voltage maintaining circuitry is weaker than the main pull-down transistor to avoid interfering with normal operation of the input terminal.