Ultra Low-Power Circuits Enable Next Wave Of Energy-Harvesting Design

Texas Instruments (TI) has unveiled five next-generation power management integrated circuits that efficiently acquire and manage microwatts (uW) to milliwatts (mW) of power harvested from light, heat or mechanical energy sources.

The bq25570, bq25505, TPS62740, TPS62737 and TPS62736 maintain the industry’s lowest 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, says the company.

Nano-power harvesting – The new bq25570 boost charger with integrated buck converter consumes a miniscule 488 nanoamps (nA) of quiescent current and achieves greater than 90-percent efficiency at output currents lower than 10 microamps (uA), maintaining high efficiency even at the lowest amount of available power. The device features maximum power point tracking (MPPT) 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, super-capacitor or conventional capacitor. During long periods of storage, power to the bq25570 can be disabled through a ‘ship mode’ feature, which allows the device to consume less than 5nA.

The bq25505 boost charger is similar to the bq25570, but achieves an even lower active quiescent current of 325nA. The bq25505 features a unique, autonomous power multiplexor gate drive that enables seamless 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 introduced the TPS62740, the smallest and lowest power buck converter for 300mA output current designs, providing 360nA of quiescent current during active operation and 70nA during standby. The converter achieves greater than 90-percent efficiency down to 10uA. Achieving a total solution size of 31mm2, the converter uses a programmable output voltage feature and DCS-Control functionality to power microcontrollers, such as TI’s ultra-low power MSP430FR59xx microcontrollers (MCUs) and BluetoothR low energy solutions, such as the SimpleLink CC2541 wireless MCU. The TPS62740′s integrated load switch also conserves the power of components like LEDs or sensors that are used temporarily.

For lower current designs, TI’s new TPS62737 converter for 200-mA designs and TPS62736 for 50-mA designs provide an ultra-low 370nA quiescent current during active operation and 15nA during sleep, while achieving 90 percent efficiency at output currents lower than 15uA, says the company.