Patent ID: 7190188

Claim:
A signal transmission system which transmits a digital signal between circuit blocks via a signal transmission line, comprising: in each circuit block, a functional circuit and a separate reception/transmission circuit; a power ground pair transmission line comprising a differential line referring to ground, led out from a differential output driver, and formed from differential signal lines disposed symmetrically with respect to ground in the circuit block; and at least one differential signal transmission line comprising differential pair lines not referring to ground, and disposed symmetrically with respect to ground, wherein, the differential signal transmission line is impedance-matched and extends between separate reception/transmission circuits of said circuit blocks, the reception/transmission circuits include a driver and/or receiver having formed in the same conductive area thereof an electrostatic discharge (ESD) protection circuit having a pull-up protection circuit and pull-down protection circuit, respectively, for each differential signal line, and which activates an ESD protection transistor in a complementary manner, and each end of the differential pair lines is a floating, open end and a grounding wire of a directional coupler or capacitor just after a driver chip, and that just before or after a receiver chip is not connected directly to the ground.