Design of High Performance CMOS Logic Circuits with Low Temperature Sensitivity

Both absolute delays and delay variations of nanoscale CMOS logic circuits, more than ever, are so heavily dependent on the thermal environment; a logic circuit operating at a high temperature, say 90°C, can see its speed drop to just half of that at 0°C. In this paper, we show two circuit techniques that can be employed to counter such severe circuit performance degradation introduced by thermal effects. First and foremost, temperature-insensitive circuit designs tend to favor implementations that use gates with smaller fan-ins (≤ 4) and have shorter logic paths. Next, the thermal-induced delay penalty can be further reduced by powering logic circuits with temperature adaptive power supplies as proposed in our prior study. Experiments on various benchmark circuits, implemented with a 45nm CMOS technology, have confirmed that, when a single fixed power supply is employed, both absolute circuit delays and temperature-induced delay variations can be reduced by more than 20% as the circuits are implemented using logic gates with small fan-ins and short logic paths. Provided a CTAT -like adaptive voltage supply to replace the single fixed power source, the same circuits will experience even smaller delay variations that fall into the range of 15%~30% for temperature varies between 0°C and 90°C, a sharp contrast to 60%~100% delay variations observed in logic circuits powered by a single constant power supply.