5 Gbit/s 2-tap low-swing voltage-mode transmitter with least segmented voltage-mode equalisation

A 2-tap low-swing voltage-mode transmitter which compensates the loss of channel at high frequency is proposed. The output driver of the proposed 2-tap transmitter consists of only two voltage-mode drivers, and thereby the design complexity of the pre-driver is greatly reduced compared with that of conventional 2^N-segmented voltage-mode drivers, where N is the number of equalisation control bits. The output impedance of each voltage-mode driver is adjusted not only to make the overall output impedance matched with the characteristic impedance of the channel, but also to achieve the desired equalisation coefficient by adopting the proposed calibration circuitry. With a high equalisation coefficient, the proposed output driver consumes less power compared with the hybrid voltage-mode driver with current-mode equalisation. The proposed transmitter is implemented using a 90 nm low-power CMOS process technology and achieves 0.79 pJ/bit without equalisation and 0.98 pJ/bit with 6 dB equalisation, at the data rate of 5 Gbit/s.