Bootstrapping and Resetting CMOS Starter for Thermoelectric and Photovoltaic Chargers

Sustaining microsensors for years is challenging because tiny batteries exhaust quickly, and recharging or replacing thousands of networked nodes is impracticable. Harnessing heat or light energy helps, but only when available. And even then, tiny generators output less than 300 mV, which is not enough to operate microelectronics well. This brief presents a 0.18-μm CMOS starter that charges a temporary 1.8-V supply quickly and reliably from slowor fast-rising photovoltaic and thermoelectric sources. For this, a jump starter helps an LC tank oscillate to a level that allows a discharge path to output power. A resetter then continually resets the circuit until the system senses the temporary supply is ready. This way, with 1.8 V, a charging system can then charge a battery quickly before the onset of another harvesting drought. The starter does not require off-chip components because it borrows the switched inductor that the charging system already uses to charge the battery. A prototype of the starter proposed charges 120 pF to 1.8 V in 15-59 μs with 1.5%-7% efficiency from a 180 Ω, 220-250-mV source.