A T-Coil-Enhanced 8.5Gb/s High-Swing source-Series-Terminated Transmitter in 65nm Bulk CMOS

Source-series-terminated (SST) drivers offer the advantage of providing a large range of termination voltages, making them particularly suitable for multi-standard I/Os. Many standards however, call for larger vertical eye openings that require raising the dc supply voltage from the 1.0 V limit for thin-oxide devices(FETs) in 65 nm technology to 1.2 or 1.5 V. These requirements are addressed in the proposed SST transmitter design by combining a thin-oxide pre-driver stage running at 1.0 V followed by thick-oxide output stages operated at 1.5 V. Key features of this design include the implementation of tri-statable output slices consisting of programmable binary-weighted pre-distortion slices to achieve a mutually independent adjustment of the impedance tuning and FIR-based transmitter equalization, the level shifter design and the application of T-coils that enable a broad-band impedance matching with a return loss of -16 dB over 10 GHz bandwidth. Moreover, the transmitter is capable to suppress the clock duty-cycle distortion by a factor of 5x.