A new fully differential 4-PAM current-mode transmitter for 10 GBPS serial links in 0.13 μm CMOS

This paper presents a new fully differential 4-PAM CMOS current-mode transmitter. Fully differential 4-PAM current-mode signaling is achieved by using differentially configured 2-bit digital to-analog conversion and fully differential current amplification. A high multiplexing speed is achieved by performing multiplexing at a low-impedance node and inductive shunt peaking with active inductors. The differential configuration of the transmitter not only minimizes the effect of common-mode disturbances, it also minimizes electro-magnetic interference asserted from channels to neighboring devices, making the multiplexer particularly attractive for high-speed data transmission over long interconnects and printed-circuit-board (PCB) traces. The transmitter draws a constant current from the supply voltage, thereby minimizing noise injection to the substrate. The proposed transmitter has been implemented in UMC´s 1.2 V 0.13 μm CMOS technology and analyzed using spectre from Cadence Design Systems with BSIM3v3 device models. Simulation results are presented.