An Active-Copper-Cable with Continuous-Time-Linear-Equalizer IC for 30-AWG 7-meters Reach Interconnect of 400-Gbit/s QSFP-DD

While a bandwidth for cable interconnects in data centers is getting to be higher, lower power-consumption and cost are required. This paper presents an active-copper-cable (ACC) with a continuous-time-linear-equalizer (CTLE) IC supporting 400-Gbit/s quad-small-form-factor-pluggable double-density (QSFP-DD) multi-source-agreement (MSA). With the cable-specific-linear-equalization, both a pass-characteristic which is compatible with a conventional short passive-copper-cable and a multi-standardization are acquired. Moreover, the heat-dissipation free design for the implementation is achieved by a far-end half-active architecture with a low power repeater. The CTLE-IC fabricated with 180-nm SiGe-BiCMOS process occupies 3.69 x 1.29 mm ² for 4-channels. In experiments, the 0.18-UI eye opening of a 56-Gbit/s/channel 4-level-pulse-amplitude-modulated (PAM4) signal at the 30-AWG 7-m ACC output was achieved with the smallest figure of merit (FOM) of 2.61-pJ/bit/channel. By introducing the QSFP-DD ACC for inner-rack and rack-to-rack connections, power and cost reductions for the next generation 400-Gbit/s interconnects can be achieved.