DC/DC converter extends battery life in WSNs

The LTC3107 harvests energy from thermoelectric generators (TEGs) and thermopiles when these sources are available, storing excess power in a storage capacitor and seamlessly transitioning to the primary cell to power a wireless sensor node when harvested power is unavailable.

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 6µA. The combination of a small step-up transformer, 3mm x 3mm package and minimal external components ensures a highly compact solution footprint.

The LTC3107 is designed to use the primary battery to start up the IC and power V_OUT 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 80nA of quiescent current drawn from the primary battery. If the energy harvesting source goes away or if the load exceeds the energy harvested, the LT3017 transitions to the primary battery to supply the V_OUT and VLDO loads. The BATT_OFF indicator can be used to track the battery usage.

The LTC3107EDD is offered in a 3mm x 3mm 10-lead DFN package, priced starting at $2.95 each for 1,000-piece quantities. An industrial grade version, the LTC3107IDD, is guaranteed to operate over the -40°C to 125°C operating junction temperature range and is priced starting at $3.45 each in 1,000-piece quantities. Both versions are available from stock.