Fully differential 8-to-1 current-mode multiplexer for 10 Gbit/s serial links in 0.18 μm CMOS

A new fully differential CMOS current-mode multiplexer where a high multiplexing speed is achieved by performing multiplexing at low-impedance node, and inductive shunt peaking with active inductors is presented. The differential configuration of the multiplexer not only minimises the effect of common-mode disturbances, particularly those coupled from the power and ground rails, but more importantly, the flow of the out currents in the opposite directions minimises the effect of electro-magnetic interference from channels, making the multiplexer particularly attractive for high-speed data transmission over long interconnects and printed circuit board (PCB) traces. The proposed multiplexer also ensures that total current drawn from the supply voltage is constant, thereby minimising the amount of noise injected to the substrate. The multiplexer has been implemented in TSMC´s 1.8 V 0.18 μm CMOS technology and analysed using Spectre from Cadence Design Systems with BSIM3.3 v device models. Simulation results demonstrate that the multiplexer offers sufficiently large eye opening when multiplexing at 10 Gbit/s.