“Time borrowing” technique for design of low-power high-speed multi-modulus prescaler in frequency synthesizer

A low power continuous phase-switching multi-modulus prescaler is proposed, based on a so called "time borrowing" method. This novel phase-switching control strategy significantly reduces the delay of the phase-switching control loop so the multi-modulus prescaler can work with higher input frequencies and obtain the maximum modulus for a lower power supply. According to the measurement results, such a multi-modulus prescaler fabricated in a 0.35 mum CMOS process divides the 2.4 GHz input frequency by 48 up to 64 for a minimum power supply voltage of 2.5 V. Its maximum power dissipation is only 4.85 mW. Compared with some other CMOS multi-modulus prescalers reported lately, our design has demonstrated a considerable improvement in terms of the power-to-speed ratio.