A mixed-mode delay-locked loop for wide-range operation and multiphase clock generation

This paper describes a mixed-mode delay-locked loop (DLL) for wide-range operation and multiphase outputs with just one clock cycle. The architecture of the proposed DLL uses the mixed-mode time-to-digital converter (TDC) scheme for phase range selector to offer faster locking time. The multi-controlled delay cell for voltage-controlled delay line (VCDL) was used to provide wide locked range and the low-jitter performance. The proposed DLL can solve the problem of the false locking associated with conventional DLLs. The circuit design and HSPICE simulation are based upon TSMC 0.258 μm 1P5M N-well CMOS process with a 2.5 V power supply voltage. The post-layout simulation results show that the proposed DLL has wide locking range 50 to 280 MHz. Moreover, the total time delay from all delay stages is precisely one period of the input reference signal, and that can generate equally spaced ten-phase clocks.