A Hybrid Line Driver with Voltage-Mode SST Pre-Emphasis and Current-Mode Equalization

The Deep Underground Neutrino Experiment requires a line driver to drive at least 25-meter long twin-axial (twinax) cables. To compensate the high-frequency loss over the long cables and alleviate the de-emphasis of the low-frequency signal magnitude, a hybrid of current-mode transmitter equalization (TXEQ) and voltage-mode pre-emphasis is proposed. The TXEQ employs a finite-impulse response (FIR) filter to boost the high-frequency components while deemphasizing the low-frequency signal magnitude, thereby flattening the overall channel frequency response and reducing Inter-Symbol Interference (ISI). Voltage-mode preemphasis is proposed to further boost the high-frequency portion without degrading the signal magnitude. The main driver utilizes voltage-mode source-series-terminated (SST) output stages, which offers higher signal swing and better power efficiency than the conventional current-mode logic (CML) drivers. Designed in 65-nm CMOS, the proposed hybrid line driver operates at 1.28 Gbps and with 6.8 mW power consumption when driving a 25-meter long twinax cable.