23-04-2010, 09:18 PM
Wireless Battery Charger Chip for Smart-Card Applications
Presented By:
Franz-Xaver Arbinger, Peter Spies, Günter Rohmer,
Fraunhofer IIS, Am Wolfsmantel 33, 91058 Erlangen, Germany
Abstract “
A chip for inductive battery charging is presented, which needs no external components except an antenna to capture the energy from an electromagnetic field. The integrated system blocks are a front-end to limit and rectify the induced alternating voltage and a charge regulator with three control loops for the current, the voltage and the temperature. The external antenna forms a resonance circuit with the on-chip capacitor. The resonance frequency of the front end is 13.56 MHz, so it is compatible to the well known smart-card standard. In the electromagnetic field of commercial reader systems the chip produces an output current to charge a lithium battery with the mandatory constant-current-constantvoltage (cccv) charge profile. This architecture is implemented to charge lithium cells at a current of 4 mA up to a cell voltage of 4.2 volts. The target application are high-end smart-cards with secondary batteries. The chip, fabricated in a 0.8 µm BICMOS-technology, includes two contacts for the antenna and two for the battery. The chip size is 1.5 mm x 2.5 mm. Also present are additional pads for testing the chip and for using a dcvoltage source for charging. The measurements of the chip show good results and the whole function has been evaluated by charging the lithium accumulators. The operating current of the IC is approximately 1 mA.
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http://iis.fraunhofer.de/Images/paper_wi...-73299.pdf
