Noise removal circuit

A noise removal circuit that asserts an output signal when an input signal continuously maintains a predetermined first level throughout a predetermined judgment time, the noise removal circuit comprising:

• a first counter that starts a count operation when the input signal transits to the first level from a second level that is a complementary level of the first level;
• a second counter that performs time counting during a time in which the input signal continues at the second level when the input signal transits to the second level after the first counter starts the count operation;
• and
• a judgment unit configured such that (i) the judgment unit holds the count value of the first counter when the input signal transits to the second level, (ii) the judgment unit resets the first counter based on a comparison result between the count value of the second counter and the count value of the first counter thus held, and (iii) when the count value of the first counter exceeds a predetermined threshold value, the output signal is asserted.

A method for detecting whether or not an input signal continuously maintains a predetermined first level throughout a predetermined judgment time, the method comprising:

• starting a count operation by a first counter when the input signal transits to the first level from a second level that is a complementary level of the first level;
• performing time counting by a second counter during a time in which the input signal continues at the second level when the input signal transits to the second level after the first counter starts the count operation;
• holding the count value of the first counter when the input signal transits to the second level;
• resetting the first counter when the count value of the second counter exceeds the count value of the first counter;
• and
• asserting an output signal when the count value of the first counter exceeds a predetermined threshold value.