A 40 mV cold-start circuit with bootstrap clock booster for thermoelectric energy harvesting

In this paper, a cold-start circuit with bootstrap clock booster for thermoelectric energy harvesting is proposed. The relationship between enhancing the clock swing amplitude and lowering the input voltage for a cross-coupled charge pump (CCCP) is analyzed. Based on the existing one-shot start-up mechanism, a series-parallel bootstrap clock booster (SP-BCB) for boosting the clock amplitude is proposed to lower the cold start voltage. Besides, a dynamic threshold MOS (DTMOS) technique for dynamically changing the threshold voltage of MOS transistors is used to achieve better conduction and leakage current suppression. The complete circuit is simulated in a 0.18-μm CMOS process. The simulated results demonstrate that using DTMOS technique and enhancing the clock swing amplitude can contribute to lowering the input voltage. The SP-BCB-based CCCP can boost the input voltage from 40 mV to 668 mV for a 500 MΩ load in 100 m s, which meets the requirement for one-shot start-up mechanism, realizing 40-mV integrated cold start for thermoelectric energy harvesting (TEH).