Capacitive coupling and quantized feedback applied to conventional CMOS technology

An on-chip capacitor is formed under the bond pad to block the DC level of input signals. Capacitively coupled signals suffer the “zero wander” effect which causes the local DC level on the second plate of the capacitor to be dependent on the bit activity rate. A quantized feedback technique using a self-triggered decision circuit is used to reestablish local DC voltage levels in the receiver and eliminates the “zero wander” effect. The input signals can be detected over a large common mode range independent of the bit activity rate and over a large frequency range. Silicon area and power dissipation are reduced since encoding and decoding of the bit stream is not required. The circuit has been implemented in silicon using a conventional digital 0.5 μm CMOS technology. This receiver can detect a 2³¹-1 pseudorandom pattern at 800 Mb/s with no errors and can operate down to a data rate of 2 kHz