A 1.0-ns/1.0-V delay-locked loop with racing mode and countered CAS latency controller for DRAM interfaces

The digital delay-locked loop (DLL) with racing mode and the countered column address strobe (CAS) latency controller are proposed in this paper. The dual-DLL architecture with racing operation is adopted to achieve low power consumption, low jitter, fast locking, wide range of locking, and stuck-free control. The merged dual coarse delay line (MDCDL) reduces the dynamic power consumption of a variable delay line by 30% by sharing a part of the delay line path in DLL. In addition, jitter is reduced by 45 ps in the 1066-DDR3 operating mode by MDCDL. The proposed DLL utilizes an or-and functioned duty cycle corrector (or-and DCC), which consumes 15% of DLL's power, 0.915 pJ/Hz at tCK = 1.5 ns and VDD = 1.575\V. The countered CAS latency controller (CCLC) saves IDD3N current because it does not need a DLL clock and does not need to be activated for IDD3N (active non-power down) state. The DLL clock is enabled and CCLC is activated only when the read command is issued. This operation condition saves the IDD3N current by 60% with the proposed DLL. The proposed DLL is employed in 128 M × 8 DDR3 SDRAM and 64 M × 16 DDR3 SDRAM. The former and the latter are fabricated by 5 × nm and by 4 × nm DRAM process technology, respectively. Experimental results show that ±10% duty error of the external clock can be corrected to within ±2% duty error in less than 512 cycles of locking time under 1.5 ns of tCK. The proposed DLL and CCLC can operate above 1.0-GHz operating frequency at 1.2 V in 5 × nm DDR3 SDRAM and at 1.0 V in 4 × nm DDR3 SDRAM, respectively. The proposed DLL fabricated with 4 × nm technology consumes 6.1 pJ/Hz at 1.575 V.