Swing-programmable SST transmitter with power-efficient de-emphasis

A novel 10 Gbit/s source-series-terminated (SST) transmitter in 65 nm CMOS technology is presented. Different from the conventional SST transmitter with the swing fixed to the supply voltage, the proposed transmitter, employing modified SST topology with switch-based shunting legs, achieves tunable swing to provide suitable a output voltage for specific channel loss, resulting in higher power efficiency for the short and medium-length channel. The proposed de-emphasis scheme operates with the shunting path connecting the differential output pins instead of the voltage supply and the ground, which is more efficient than the conventional way. Fewer slices for de-emphasis are needed along with less parasitic capacitance, and thus the power efficiency is improved. A full-rate delay-matching pre-driver is used to avoid a complicated structure. Swing ranges from 50 mV to 1.2 V at a 1.2 V supply. The de-emphasis could be tuned from 0 to -15.5 dB with power consumption dropping from 15.6 to 13.3 mW at the nominal swing of 1.2 V.