Design of low-voltage high-speed CML D-latches in nanometer CMOS technologies

This paper presents the design of a novel low-voltage high-speed D-latch circuit suitable for nanometer CMOS technologies. The proposed topology is compared against the low-voltage triple-tail D-latch and its advantages are demonstrated both by simulations, under different performance/power consumption tradeoffs with a 40-nm CMOS technology, and theoretically, thanks to a simple model of the propagation delay derived for both low-voltage topologies. In order to further demonstrate the advantages of the proposed topology, it has also been used to design a D flip-flop (DFF), where thanks to the feature to need just 1 clock differential pair; a further speed improvement is achieved over the conventional triple-tail topology. Indeed, by comparing a two-stage frequency divider designed using both the triple-tail DFF and the proposed folded DFF, a 54% improvement in the maximum operating frequency is found when using the proposed folded DFF.