Three-level detector without standby current

Abstract

A three-level detector is used to detect the state of a level input pertaining to a relatively-high level, a relatively-low level, or floating. The three-level detector comprises a first inverter, a second inverter, a decision logic circuit, a switching circuit, and a latch. The first inverter and the second inverter, whose inputs are connected to the level input, have a relatively-high threshold voltage and a relatively-low threshold voltage, respectively. The decision logic circuit generates a detected signal representing the state of the level input in response to outputs of the first and second inverters. Moreover, the switching circuit is connected between the level input and a reference level. The latch generates one control signal to regulate the state of the switching circuit. When the state of the level input pertains to either the relatively-high level or a relatively-low level, the switching circuit is turned off. The switching circuit is turned on when the state of the level input is floating.

Dependencies are inferred from the claim text.