DSP-based 5 V Qi wireless charger in 5 x 5 mm
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.
The reference design for the NXQ1TXA5 forms a complete wireless charger designed to meet low-power Qi A5/A11 specifications for 5-V chargers and can be powered by standard USB wall chargers or PC USB ports. The company’s high-efficiency GreenChip™ TEA1720 SMPS controller complements this low-power reference design to achieve overall low-power standby operation.
The two other reference designs in the NXP wireless charger transmitter devices family include the NXQ1TXA6, designed to meet the Qi A6 standard for 12-V, as well as the NXQ1TXA1 which is designed to meet Qi A1/A10 standard for 19-V charging transmitters. Both the NXQ1TXA1 and NXQ1TXA6 come in a small package of 7-mm square with only 32 pins spaced 0.5-mm apart for easy PCB design. NXP provides a complete low component count reference design based on NXQ1TXA1 and NXQ1TXA6, with other high-performing components of its portfolio such as the GreenChip NWP2081 half-bridge driver, and NX2020N2 low RDS(on) trench MOSFETs for the coil-driving power bridge.
NXP’s reference designs for its wireless charger transmitter devices will be made available in Q2 for selected customers, and the parts will be qualified for mass production in Q3.