A T-coil-enhanced 8.5 Gb/s high-swing SST transmitter in 65 nm bulk CMOS with < 16 dB return loss over 10 GHz bandwidth

Abstract

A source-series-terminated (SST) transmitter in a 65 nm bulk CMOS technology is presented. The circuit exhibits an eye height greater than 1.0 V for data rates of up to 8.5 Gb/s. A thin-oxide pre-driver stage running at 1.0 V drives 22 parallel connected thick-oxide SST output stages operated at 1.5 V that feature a 5-bit 2-tap FIR filter whose adaptation is independent of the impedance tuning. To achieve a return loss of - 16 dB up to 10 GHz a 40 μ m\,×, 40 μ m T-coil complements the transmitter output. This half-bit-rate clock SST transmitter has a duty-cycle restoration capability of 5x, and the common-mode voltage noise is below 10 mV rms for high-, mid- and low-level terminations. The chip consumes 96 mW at 8.5 Gb/s and occupies 180 μm ×, {360}\ μm. In addition to the transmitter design, guidelines for the T-coil design are presented. © 2006 IEEE.