Comparison of Two ADPLL Structures for IoT Applications

All digital Phase locked loop (ADPLL) based wireless transceiver is a key block in IoT based wireless communications. Locking time, power consumption and frequency resolution of ADPLL are the most important parameters to be considered in increasing the efficiency of IoT applications. ADPLL consist of three components namely phase detector, loop filter and Digital controlled oscillator and the performance of above mentioned parameters depends on components Of ADPLL. In this paper two ADPLL structures, ADPLL with bang bang phase detector, Digital loop filter and Ring based oscillator and ADPLL with bang phase detector, loop filter , Bootstrapped ring oscillator with TDC are compared based on important parameters such as Locking time, frequency resolution, output frequency and phase noise and it is found that ADPLL with bang phase detector, loop filter, Bootstrapped ring oscillator with TDC is best suited for IoT applications. The output frequency is 3.5 GHz. The functional verification and simulation can be done using Xilinx ISE tool.