SymmTop: A Symmetric Circuit Topology for Ultra Low Power Wide Temperature-Range Applications

A major roadblock for ultra-low power (ULP) circuits lies in increased sensitivity to process variations at near- and sub-VT. Additionally, temperature variations can be detrimental to circuit functionality for energy harvesting applications operating in outdoor environments. This vulnerability to variations at the device level is exacerbated by imbalances between pull-up (PUN) and pull-down (PDN) networks at the circuit level. In this paper, we propose Symm Top, a symmetric circuit topology in conjunction with a biasing scheme that maintains symmetrically robust operation of ULP energy harvesting systems in a variety of climates, including extreme temperatures. Through noise-analysis and Monte Carlo (MC) simulations performed in a commercial 28nm Fully Depleted Silicon On Insulator (FDSOI) technology, we demonstrate the robustness to variations and extreme temperature ranges of the proposed symmetric 2-to-1 multiplexer design (mirror mux) with bias compared to conventional 2-input NAND and NOR-based circuits. The linearity between temperature and bias makes this scheme easily applicable for programmable sensors in a variety of applications requiring environmental adaptability.