Signal Integrity Co- Design of a High-Speed (20 Gbps) Analog Passive CMOS Switch

A switch (digital or analog) is an integrated circuit (IC) that connects and disconnects an electrical circuit or two separate subsystems. Switches are one of the most ubiquitous electrical circuit components today. However, with broad applications covering multiple market segments, meeting device performance requirements are becoming challenging. Analog switches, configured as multiplexers ( mux) or demultiplexers (demux), are designed to pass or isolate analog signals by switching on and off CMOS transistors. However, designing highperformance, high-speed (> 20 Gbps) bi-directional analog CMOS-based passive switches to support system-level end-to-end signal chains is typically plagued by signal integrity and timing issues. Common issues observed in high-speed analog passive switches design are meeting bandwidth, insertion loss, return loss, channel-to-channel crosstalk, OFF isolation, and THD+ (total harmonic distortion) noise. Additionally, the drive for continued miniaturization and highly- integrated switch exacerbates electromagnetic interactions between the system components (i.e., silicon + package + PCB). As such, signal integrity issues are aggravated with a potential impact on system performance if not considered and addressed early in the design phase. This paper presents the package-PCB system electrical co-design and measurement validation results of an analog passive CMOS Mux/Demux device that can support high-speed differential data transmission. We detail how electrical co-optimization of the package-PCB system interaction was achieved through a coupled circuit-to-electromagnetic modeling and simulation methodology. Laboratory measurements on a 4-Channel 20 Gbps Differential 2:1/1:2 Mux/Demux IC are presented that validate the integrity of the co-design modeling and simulation methodology.