US Patent 7224188 Line driver with reduced interference

A bus communication system contains a pair of communication conductors and a driver. The driver contains a plurality of pairs of controlled current source circuit, each pair comprising current source circuits of a first and second, mutually opposite polarity, and a control circuit for matching currents drawn by the current sources in each pair. The current source circuit of the first polarity have outputs coupled to a first one of the communication conductors, the current source circuits of the second polarity have outputs coupled to a second one of the communication conductors. A delay line is provided, with taps coupled to control inputs of the current sources of the first and second polarity, so that the pairs are switched on successively with mutual delays between successive pairs, as determined by the delay line.