The application belongs to the field of integrated circuits, and discloses a polarity pulse modulation and
demodulation circuit applied to isolated communication, which comprises a first
delay circuit, a second
delay circuit, an
AND gate, a NOT gate, a pulse
driving circuit, a
transformer, a pulse detection circuit and an SR flip-flop; the first input end of the
AND gate is connected with the output end of the first
delay circuit, the second input end is used for inputting a
digital signal, and the output end is connected with the pulse
driving circuit; the first input end of the NOT gate is connected with the output end of the second delay circuit, the second input end is used for inputting an input
signal, and the output end is connected with the pulse
driving circuit; the primary side of the
transformer is connected with the pulse driving circuit, and the
secondary side is connected with the pulse detection circuit and the SR flip-flop in sequence. The delay circuit has the characteristics of stable
delay time, which guarantees the certainty of the pulse width of the transmitted pulse
signal, and then the pulse amplitude of the pulse
signal is controlled through the pulse driving circuit, so that the pulse signal can realize long communication distance in a typical
twisted pair line.