Step-up energy-harvesting sources from milliVolt levels

February 28, 2014 // By Graham Prophet
An ultra-low-voltage energy harvester and power manager IC aims to extend the useful life of primary batteries in wireless network devices

LTC3107 is a highly integrated DC/DC converter designed to extend the life of a primary battery in low power wireless system networks (WSNs). It combines energy harvesting and power management capability with a primary battery cell. The LTC3107 harvests energy from thermoelectric generators (TEGs) and thermopiles when these sources are available, storing excess power in a storage capacitor and transitioning to the primary cell to power a wireless sensor node when harvested power is unavailable. Its reserve energy output is clamped at 4.3V.

The LTC3107’s internal boost converter, combined with a small step-up transformer, harvests energy from input voltages as low as 20mV, commonly found from sources such as TEGs and thermopiles, and delivers an output which tracks the battery voltage. An additional 2.2V LDO output provides power to an external microprocessor. If harvested energy is not available, the system is powered directly from the battery, requiring only 6 µA. The combination of a small, standard step-up transformer, 3 x 3 mm package and minimal external components ensures a compact solution footprint.

The LTC3107 is designed to use the primary battery to start up the IC and to power VOUT and the LDO, with or without any available power from the energy harvesting source. When the energy harvesting source is available, the LT3107 seamlessly transitions to run only from the energy harvesting source with only 80 nA of quiescent current drawn from the primary battery. If the energy harvesting source shuts down or if the load exceeds the energy harvested, the LT3017 transitions to the primary battery to supply the VOUT and VLDO loads. The BATT_OFF indicator can be used to track the battery usage.

In a 10-lead DFN package, it costs $2.95 (1,000) or an industrial temperature version is $3.45.

Linear Technology;