A 20 Gbps PAM4 data transmitter ASIC for particle physics experiments

We present the design and test results of a novel data transmitter ASIC operating up to 20.48 Gbps with 4-level Pulse-Amplitude-Modulation (PAM4) for particle physics experiments. This ASIC, named GBS20, is fabricated in 65 nm CMOS technology. Two serializers share 5.12 GHz Phase Locked Loop (PLL) clock. The outputs from are combined into PAM4 signal that directly drives Vertical-Cavity-Surface-Emitting-Laser (VCSEL). input channels, each at 1.28 Gbps, scrambled an internal 27-1 Pseudo-Random Binary Sequence (PRBS), which also serves as frame aligner. GBS20 tested work 10.24 VCSEL-based Transmitter-Optical-Subassembly (TOSA). power consumption below 238 mW reduced 164 low-power mode.