Patent ID: 6335641
Filing Date: 2002-01-01
Classification: G01R,H03K

Abstract:
An automatic input threshold selector comprising:level decision means for deciding, among a plurality of level ranges determined by a predetermined number of decision levels, a level range to which a level of an input signal belongs; and input threshold setting means for selecting, in response to the level range decided by said level decision means, at least one of input threshold candidates from among a predetermined number of input threshold candidates, wherein said level decision means decides, among the plurality of level ranges, a level range to which one of a maximum value and a minimum value of the input signal belongs; and said input threshold setting means selects, in response to the level range decided by said level decision means, at least one of n input threshold candidates, where n is a natural number, wherein said level decision means comprises: a reference level selecting switch for selecting one of the predetermined number of decision levels as a reference level; a first voltage comparator for comparing the input signal with the reference level; a logic gate for carrying out on-off control of a clock signal in response to an output signal of said voltage comparator; a shift register for shifting, in response to an output signal of said logic gate, its output state every time the input signal crosses the reference level in one of rising and falling directions of the input signal; and a decoder for outputting signals for identifying the level range of the input signal in response to output signals of said shift register, wherein said reference level selecting switch selects the reference level in accordance with the output signals of said decoder, and wherein said input threshold setting means comprises: an input threshold selecting switch for selecting, in response to the outputs of said decoder, one of the n input threshold candidates as the input threshold, and wherein said automatic input threshold selector further comprises a second voltage comparator for comparing the input signal with the input threshold.