Patent ID: 8035424

Claim:
An AC-coupled interface circuit on a semiconductor integrated circuit apparatus performing a bidirectional data transfer via a differential transmission line, the AC-coupled interface circuit comprising: a pair of signal lines configured to transfer a differential signal; a pair of capacitors configured to AC-couple the pair of signal lines with the differential transmission line; a resistor element configured to connect the pair of signal lines to each other; a differential driver including a pair of output terminals connected to the pair of signal lines, wherein in a data transmission operation, the differential driver receives transmit data and converts the transmit data to a differential signal to output the differential signal; a differential receiver including a pair of input terminals connected to the pair of signal lines, wherein in a data reception operation, the differential receiver receives a differential signal transferred to the pair of signal lines and converts the differential signal to receive data; a potential setting section configured to set a potential of the pair of signal lines to a predetermined stable potential before the differential signal is transferred to the pair of signal lines; and a feedback control section, wherein when an output of the differential signal by the differential driver is started, the feedback control section detects an amplitude of the differential signal of the pair of signal lines and compares the detected amplitude of the differential signal with a predetermined reference amplitude value so as to control an amount of output current of the differential driver based on a comparison result.