Entering the increasingly attractive arena for energy-harvesting ICs and support, the bq25504 from Texas Instruments is a boost charger which manages the extraction of microwatts and milliwatts from solar, thermal, electromagnetic (RF) , and vibration transducers as sources, and manages the storage of the energy in batteries and supercapacitors.
In addition to the basic harvesting function, the IC protects the storage element from over- and under-voltage conditions which can cause damage. It has a low cold-start level of 330 millivolts, to initiate the system operation when the storage element is deeply discharged. It also includes a MPPT (maximum power point tracking) function to optimize the energy quantity being extracted, a consideration especially useful with solar panels (varying light conditions) and thermoelectric generators (TEG).
Key features and performance parameters include:
•Low quiescent current (typically, 330 nA) and conversion efficiency >80% (see Figure below).
•User-programmable settings so the IC can be used with different storage devices, such as various battery chemistries.
•The 330 mV cold-start parameter means that the IC can be used in low-light, single-cell solar panel or low temperature-differential TEG situations.
•A "battery OK" indication so the system designer can set up the application to shed/enable external loads, as well as protect the storage element.
Packaging, pricing, and availability: The bq25504 is housed in a 16-lead, 3×3 mm VFQN package, and is priced at $2.10 (1000 pieces); it is available now.
For more information: go to http://www.ti.com/bq25504-pr. An evaluation module is available for the IC, go to http://www.ti.com/bq25504evm-pr for more on the module.