3.48mW 2.4GHz range Frequency Synthesizer Architecture with Two-Point Channel Control for Fast Settling Performance

A new frequency synthesizer architecture with low-power and very short settling time is introduced for 2.4GHz ZigBee applications. It uses two-point channel control with divider control and direct VCO control. A DAC with tunable gain is used along with a linearized varactor for the direct VCO control path. Despite the use of an integer-N architecture with 50kHz loop bandwidth, we have achieved a frequency settling time of less than 10musec for 80MHz frequency jumping from 2400MHz. The proposed modified-TSPC circuit topology with 2-transistor stacks operational with lower supply voltage is used for the high frequency divider circuits. With a lowered supply voltage of 1.0V, the power consumption is significantly reduced and so is the switching noise induced by TSPC and digital circuits. With the -112 dBc/Hz phase noise at 1MHz offset from 2.44GHz, total power consumption using 0.18mum CMOS technology is only 3.48mW