A 280mv Input Fast Transient Startup Charge Pump with a 4 Phase Ring Oscillator for Energy Harvesting Applications

A six-stage 4-branch startup charge pump for energy harvesting application is presented. Using dynamic body biasing techniques on NMOS Charge transfer switches (CTS's) and applying boosted gate control scheme on PMOS CTS's, raise the charge transferability of structure in the subthreshold region. Furthermore, an ultra-low power quadrature phase generator provides clock signals of 4 pumping branches in the frequency of 5.09MHz. The proposed 6 stage charge pump circuit is designed in a standard 0.18 μm CMOS process with120 pF and 20 pF, total pumping capacitance and load capacitance, respectively. The output voltage of the proposed structure can rise from 300mv to 1.99v within 135ns. With a conversion efficiency of 94.7%, the minimum startup voltage of the proposed charge pump is 280mv.