Floating detection circuit

Abstract

A floating detection circuit detects the floating state of an input node which can receive an externally applied DC input signal, and includes a pulse generator, a counter and a floating state discriminator. The pulse generator is coupled to the input node and supplies a pulse signal to the input node when the input node is in a floating state. The counter receives the pulse signal and counts the number of pulses included in the pulse signal during predetermined intervals. The floating state discriminator compares the number of pulses with a predetermined reference number, so as to produce a floating detection signal, wherein the floating detection signal indicates whether or not the input node is in a floating state. A semiconductor circuit includes this floating detection circuit and a DC level detector. The floating detection circuit included in the semiconductor circuit detects the input node state during a first period and produces the floating detection signal during a second period. The DC level detector is coupled to the input node and measures the level of the DC signal applied to the input node during the second period when the input node is not in a floating state.