A large-swing transformer-boosted serial link transmitter with >VDD swing

The design and analysis of a large-swing transformer-boosted serial link transmitter is described. Transformer boosting is used to produce a signal swing that is not constrained by the supply voltage and enables a true pre-emphasis transmitter with a differential output swing greater than the supply. The boosted signal is separated from the driver through series inductors and therefore does not stress the transistor voltage tolerance. Several design tradeoffs between the amounts of boosting, power, and output matching are examined in both analysis and simulation. Distributed boosting is employed to relax the tradeoff between the amount of boosting and output matching degradation. Implemented in a 0.13-mu m CMOS technology, the prototype chip produces an 8-Gb/s PRBS 2(31)-1 data pattern and achieves a 1.42 V-PP differential output swing while drawing 137 mA current from a 1.2-V supply. The measured output reflection coefficient is better than -10 dB up to 4 GHz.