Khang Yian NgHarikrishnan RamiahTian Siang HoYi Chen LeeTeck Seong ChangEn Hao Lee0009-0005-9827-4302Yee Chyan TanYong Chen2026-10-212026-10-21202610.1109/ACCESS.2026.3677803https://dspace-cris.utar.edu.my/handle/123456789/11813This paper presents a review of capacitive cold-start-up charge pump (CSUCP) architectures and the design challenges of ultra-low-voltage energy harvesting systems. In addition to the surveyed implementations, the underlying operating principles and design concepts of each approach are explained in detail. This study further reviews and consolidates analytical models related to subthreshold conduction, charge transfer, and loss mechanisms. An overview of the oscillator and charge pump interaction is provided as structured design guidance for CSUCP selection and optimization. Key performance tradeoffs, including minimum start-up voltage, voltage conversion efficiency, power conversion efficiency, and start-up robustness, are systematically examined across different CSUCP mechanisms. To illustrate practical design constraints, temperature-dependent simulations adapting the representation of Dickson and cross-coupled charge pump topologies are included to observe environmental variation effects on subthreshold conduction and leakage behavior. By evaluating the relation of architectural mechanisms with analytical design considerations, this review clarifies how different CSUCP techniques address specific performance bottlenecks and provides a unified perspective to support informed CSUCP design under constrained energy conditions. © 2026 The Authors.en-USbattery-lesscharge pumpCold start-upenergy harvestingpower autonomyCharge pump circuitsComputer aided designConversion efficiencyPumpsBattery-lessCharge-pumpCold-startDesign challengesEnergyPower autonomyPump mechanismSubthreshold conductionUltra-low-voltageEnergy harvestingtext::journal::journal article::review article