DSP-based 5 V Qi wireless charger in 5 x 5 mm

February 26, 2014 // By Jean-Pierre Joosting
At Mobile World Congress, NXP Semiconductors is demonstrating a revolutionary Qi wireless charging transmitter device, which integrates all the circuits for a 5-V mobile phone charger in an extremely small package measuring only 5-mm square.

Using this device, fewer than 10 external components are needed to build a complete low-power 5-V Qi A5/A11 wireless charging transmitter, alongside the Qi coil and resonant capacitors. The tiny footprint of the NXQ1TXA5 system-on-chip means that the whole transmitter sits on a PCB of less than 1.5 cm-square with components on a single side. This opens up interesting possibilities for innovative wireless charging pad designs, including fitting the transmitter within the center of the Qi coil.

In addition, the company is demonstrating two “smart” wireless charging reference designs for 12-V and 19-V Qi transmitters, featuring NFC (Near Field Communication) technology. By adding NFC, wireless chargers can offer a wide range of additional functionality. Consumers can configure wireless charging pad settings via any NFC-enabled phone or tablet, and NFC could be used to trigger “wake up” of the wireless charger, thus enabling zero standby current when not in use. Other smart features include automatic Bluetooth pairing, or launching applications and web sites when an NFC-enabled phone is put on the charging pad.

The NXQ1TXA5 system-on-chip integrates a power controller, DSP, voltage regulation, Foreign Object Detection (FOD), a full-bridge power stage to drive the transmitter coil, and circuits for on-chip current and voltage measurement — leaving very few external components to complete the implementation. Using the NXP CoolFlux™ DSP technology, the device is extremely power efficient, achieving standby power of under 2 mW.