| 摘要 |
A CMOS driver circuit (20) has a high impedance driver (30) and a low impedance driver (36) connected to the near end of a transmission line (43). The output impedance of the high impedance driver (30) matches the characteristic impedance of the transmission line (43). As a digital signal from the CMOS driver circuit (20) transitions from one logic state to another, the low impedance driver (30) drives the transmission line (43) until a predetermined voltage before the signal reaches its steady state voltage. A sensing circuit (24) senses when the predetermined voltage is reached, and in response, provides a control signal to deactivate the low impedance driver (36). The high impedance driver (30) completes the signal transition. The high impedance driver (30) absorbs the reflected waves from the far end of the transmission line (43), reducing the effects of ringing, and increasing noise immunity.
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