Multi-band PLL for RF wireless charger at 2.4 GHz and 5.8 GHz

This paper presents an integer-N Phase Locked Loop (PLL) for the use in RF wireless charger systems. The presented design supports 4.3 GHz to 6.3 GHz bands using a push-pull Class-C Voltage Controlled Oscillator (VCO) structure. The 2.4 GHz frequency is generated by dividing 4.8 GHz by 2 times to reduce current consumption. Reference spur levels are lower than -45 dBc. The PLL consumes less than 36 mW from a 1.8 V power supply with a settling time less than 40 μs and the area is 1200 μm × 1100 μm in the TSMC 180 nm CMOS process.