Adaptive on-die termination resistors for high-speed transceiver

As the demand of data transmission bandwidth is increased, the issue of impedance matching becomes important factor for the high-speed serial link transceiver. Especially, there are many standards of the characteristic impedance in today's transmission media. We propose a digital approach of on-die adaptive termination resistors in the transceiver. It can match the characteristic impedance of coaxial cable automatically from 75 /spl Omega/ /spl sim/45 /spl Omega/ without any external component and bias. Using tsmc 0.18 /spl mu/m CMOS process, the tuning process can be finished in 14 clock cycles and the difference between termination resistor and coaxial cable is less than 5/spl Omega/ for the range of characteristic impedance from 75 /spl Omega/ to 45 /spl Omega/.