Serial bus interface circuit

An interface circuit for a serial bus, the interface circuit comprising:

• a receiving terminal for receiving an input signal having a first signal level and a second signal level;
• an output terminal for outputting a first voltage signal;
• a first switching circuit coupled to the receiving terminal, the output terminal and a grounded terminal, for determining a coupling relationship between the output terminal and the grounded terminal according to difference between the input signal and a grounding voltage provided by the grounded terminal;
• a voltage source for producing a voltage drop based on a driving voltage to provide a first voltage, the driving voltage driving the serial bus interface circuit;
• a second switching circuit coupled to the receiving terminal, the first switching circuit, the output terminal and the voltage source, for determining a coupling relationship between the first switching circuit and the voltage source according to difference between the input signal and the first voltage;
• a first switch coupled between the voltage source and the second switching circuit, for determining a coupling relationship between the voltage source and the second switching circuit according to a first control signal;
• a second switch coupled to the second switching circuit, for determining a coupling relationship between the driving voltage and the second switching circuit according to a second control signal;
• and
• a controlling unit coupled to the output terminal, for generating the first control signal and the second control signal according to the first voltage signal;
• wherein the first switching circuit eliminates generation of a first current flowing from the voltage source to the grounded terminal when the input signal is at a steady state of the first signal level, and the second switching circuit eliminates the generation of the first current when the input signal is a steady state of the second signal level.