Patent ID: 7734940

Claim:
A data communication device, comprising: a signal terminal for inputting a received signal having portions of different duty ratios and a constant pulse frequency; a reference voltage terminal for inputting a first reference voltage; a clock generation circuit for generating a clock signal according to the received signal; a data signal generation circuit for generating a data signal by identifying a duty ratio of the received signal; a transmission circuit for outputting a transmission signal to the signal terminal; a regulator circuit for generating power supply voltages of the clock generation circuit, the data signal generation circuit, and the transmission circuit on a basis of an internally generated second reference voltage, the received signal, and the first reference voltage; and a reference voltage circuit for generating the second reference voltage; and a level shift circuit for level-shifting a pulse of the received signal on a basis of a threshold correlated with the second reference voltage, wherein the regulator circuit generates a power supply voltage correlated with the second reference voltage, and there is a correlation between the threshold and the power supply voltage.