This paper presents a frequency-estimation algorithm for the ADPLL designs instead of traditional binary frequency-search algorithm. With the proposed ADPLL architecture and synchronization process, the lock time can be optimized to two cycles. As the reference clock varies or frequency multiplication switches, lock time holds in two reference clock cycles. An implementation of proposed ADPLL design is realized in UMC 0.18 mum 1P6M CMOS technology with core area of 520times530 mum². The PLL has the frequency range of 140 MHz to 1030 MHz with 22ps DCO resolution