A 10mA shunt allows simple charging of the battery with harvested energy while a low battery disconnect function protects the battery from deep discharge. The rechargeable battery powers a synchronous buckboost converter that operates from 1.8V to 5.5V at its input and is used when harvested energy is not available to regulate the output whether the input is above, below or equal to the output. The LTC3331 battery charger has a very important power management feature that cannot be overlooked when dealing with micro-power sources. TheLTC3331 incorporates logical control of the battery charger such that it will only charge the battery when the energy harvested supply has excess energy.
Without this logical function the energy harvested source would get stuck at startup at some non-optimal operating point and not be able to power the intended application through its startup.A supercapacitor balancer is also integrated allowing for increased output storage. In July of 2015, Linear is going to introduce the LTC3335 – a nanopower buck-boost DC/DC converter with an integrated coulomb counter aimed at wireless sensor networks and general purpose energy harvesting applications. It is a high efficiency, low quiescent current (680nA) converter. Its integrated coulomb counter monitors accumulated battery discharge in long life battery powered applications.