Energy harvesting chips enable battery-free operation

The bq25570, bq25505, TPS62740, TPS62737 and TPS62736 are designed to maintain ultra low levels of active quiescent current and enable battery free operation to wireless sensor networks, monitoring systems, wearable medical devices, mobile accessories and other applications with limited access to power. The bq25570 boost charger with integrated buck converter features maximum power point tracking to extract and manage power from photovoltaic cells and thermoelectric generators, and supports any energy storage element, such as a rechargeable Li-ion battery, thin film battery, supercapacitor or conventional capacitor. The device is designed to consume just 488nA of quiescent current and achieve greater than 90% efficiency at output currents lower than 10uA. The bq25505 boost charger is similar to the bq25570, but is designed to achieve an even lower active quiescent current of 325nA. The bq25505 features an autonomous power multiplexor gate drive that enables faultless system operation from energy harvesting sources and the primary battery, ensuring constant power is available when the system needs to operate, even when no energy is available from the harvester. In addition to the battery management circuits, TI has also introduced the TPS62740 - an ultra small and low power buck converter for 300mA output current designs which provides 360nA of quiescent current during active operation and 70nA during standby. For lower current designs, the TPS62737 converter for 200mA designs and TPS62736 for 50mA designs provide an ultra low 370nA quiescent current during active operation and 15nA during sleep, while achieving 90% efficiency at output currents lower than 15uA.