Jae-il Kim

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 DLLs 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.

25.3 A 1.35V 5.0Gb/s/pin GDDR5M with 5.4mW standby power and an error-adaptive duty-cycle corrector

The demand for high-bandwidth memories is increasing with an increase in the need for high-performance systems. Wide-I/O memory and GDDR5 are two types of high-bandwidth memories. GDDR5 is more compatible than wide I/O for contemporary systems, such as graphics cards and game consoles. The datarate of GDDR5 has reached 7Gb/s/pin. However, the power consumption and cost have increased owing to high-performance-oriented designs, die penalties, and additional test costs. DDR4 is an alternative low-cost memory with high performance in the range of 2.4 to 3.2Gb/s/pin [1]. However it is difficult for DDR4 DRAM to raise the 3.2Gb/s/pin bin portion to lower the cost. In DRAMs, the standby power and self-refresh power are more important than the operating power because DRAMs are mainly in the standby or self-refresh mode in systems. As the operating speed increases, the data window is narrowed, and the jitter increases. Therefore, a duty-cycle corrector (DCC) is employed to increase the data window when the external clock duty cycle is distorted in GDDR5 [2]. The bang-bang jitter caused by the DCC is inevitable even if the external clock duty ratio is exactly 50%. Sometimes the DCC may distort the data window because of an internal DCC offset. This paper presents a GDDR5M (mainstream) memory for graphics cards and a small-outline dual-inline memory module (SO-DIMM). The standby power is managed by the auto-sync mode. Additionally, the architecture of GDDR5M is similar to that of DDR4, and not GDDR5. The error-adaptive DCC can remove the initial duty-cycle offset automatically and remove the bang-bang jitter when the duty cycle of the external clock is not distorted.

A 7.7mW/1.0ns/1.35V delay locked loop with racing mode and OA-DCC for DRAM interface

A 7.7mW/1.0ns/1.35V digital delay locked loop has been proposed in this paper. The dual-DLL architecture with racing operation is adopted to achieve low power operation and low jitter, which is primarily caused by the length of the delay line. The merged dual coarse delay line (MDCDL) is employed for low power and high frequency operation. This DLL utilizes an OR-AND DCC for wide duty cycle correction capability. The proposed DLL for DDR3 SDRAM is fabricated by a 54nm DRAM process technology. Experimental results show that ±10% duty error of external clock can be corrected in less than 400 cycles locking time with 1.0GHz operation frequency at 1.35V.