A transceiver macro for high-speed data transmission via cable in vehicles is proposed. The transceiver uses ac coupling and bidirectional interface topology for protecting LSIs against unexpected short of cable and harness/chassis and has a spread-spectrum-clocking (SSC) generator that reduces noise due to electromagnetic interference. A driver current control has been used for fast switching of data direction on accoupled interfaces. An adaptive bandwidth control has been used in a ΔΣ PLL to improve SCC significantly. A test chip has been fabricated and shows stable and bi-directional data communication with data rate of 162 to 972 Mbps through 20-m cable. Thanks to an optimum calibration of the SSC-PLL bandwidth, it reduces peak power at 33kHz by -23dB and provides 2% modulation at a data rate of 810Mbps.