Young Jung Choi

A One-Cycle Lock Time Slew-Rate-Controlled Output Driver

A low-power output-on-demand slew-rate-controlled output driver is presented. It has an open-loop digital scheme and a one-cycle lock time applicable to high-speed memory interfaces. The output driver maintains slew rate between 2.1V/ns and 3.6V/ns for the SSTL interface. Fabricated in a 0.18mum CMOS process, the control block of the proposed driver occupies 0.009mm2 and consumes 13.7mW at 1Gb/s. No external resistance is needed to calibrate the output resistance of the output driver.

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.

A 2.5Gb/s/pin 256Mb GDDR3 SDRAM with Series Pipelined CAS Latency Control and Dual-Loop Digital DLL

A series pipelined CAS latency control with voltage-controlled delay line that extends maximum data rate to 2.5Gb/s/pin at 1.7V, is presented. Other schemes applied in the DLL are dual loop control that increases power noise immunity and LPDCC that achieves low power consumption. All these schemes are implemented in a 8M times 32 device using a 0.10 mum DRAM process

A 0.1-to-1.5GHz 4.2mW All-Digital DLL with Dual Duty-Cycle Correction Circuit and Update Gear Circuit for DRAM in 66nm CMOS Technology

We design a DLL that has a slew-rate controlled duty-cycle-correction (DCC) with a fully digital controlled duty-cycle-error detector and has the update gear circuit to shift update mode for low power consumption. The DLL is composed of a dual loop and two types of digital DCC, at the input and output, which have a higher DCC capability when combined. We also design a clock receiver that generates a robust clock from a poor clock source.

A 7ps-Jitter 0.053mm2 Fast-Lock ADDLL with Wide-Range and High-Resolution All-Digital DCC

An ADDLL is designed to achieve low jitter, fast lock time and nearly 50% duty cycle with an open-loop duty-cycle corrector. The ADDLL operates over a frequency range from 440MHz to 1.5GHz with 15 cycles of maximum lock-in time and occupies 0.053mm2 in 0.18mum 1.8V CMOS. The peak-to-peak jitter is 7ps at 1.5GHz and the power consumption is 43mW.

Multi-Slew-Rate Output Driver and Optimized Impedance-Calibration Circuit for 66nm 3.0Gb/s/pin DRAM Interface

In this work, a multi-slew-rate output driver is developed to cope with the supply voltage variation and the different I/O component capacitance (denoted by CIO) condition. For accurate data transfer, it is necessary to reduce the design loss in the impedance-calibration circuit and to minimize CIO in the coded output driver. With these methods, a data rate of 3 Gb/s/pin is achieved and the shmoo plot. The micrograph of the output driver and impedance calibration circuit, which is implemented in a 66 nm 512 Mb GDDR3 SDRAM.

A wide-range all-digital multiphase DLL with supply noise tolerance

An 80-to-832 MHz all-digital 8-differential-phase DLL in a 0.18 um CMOS process has been developed to achieve low-jitter and supply noise tolerance using dual window phase detector, noise tolerant delay cell and delay compensation under supply noise. The proposed DLL occupies 0.19 mm2 and dissipates 48 mW at 832 MHz from a 1.8 V supply. The peak-to-peak jitter and rms jitter are 12 ps and 1.73 ps with a quiet supply at 832 MHz, respectively. The peak-to-peak and rms jitter with a 100 mV peak-to-peak triangular supply noise at 100 MHz are 21 ps and 2.99 ps, respectively.

A 0.17–1.4GHz low-jitter all digital DLL with TDC-based DCC using pulse width detection scheme

A wide-range low-jitter digital DLL using 0.18 um single-poly four-metal CMOS technology is proposed that uses an open-loop time-to-digital converter (TDC)-based DCC circuit with 10 cycles of maximum locking time by virtue of pulse width detection scheme. In addition, the DLL uses a semi dual delay line to remove the boundary switching problem and to optimize its area and power consumption. Thus, the proposed DLL operates over a frequency range from 170 MHz to 1.4 GHz. The peak-to-peak jitter is 13.8 ps at 1.4 GHz and the power consumption is reduced to 27 mW.

A fast-lock synchronous multi-phase clock generator based on a time-to-digital converter

An all-digital fast-lock synchronous multi-phase clock generator is presented. By using a time-to-digital converter for fast-lock operation and delay measurement, the proposed multi-phase clock generator generates four-phase clocks and synchronizes the reference clock with the output clock within 45 cycles. Furthermore, the clock generator uses a fine binary scheme and de-skewing circuit for fine delay measurement and compensation. The proposed clock generator was designed in a 0.18um CMOS technology. It operates over a wide frequency range from 400MHz to 1.22GHz and consumes 34mW at 1.22GHz.

An adaptive-bandwidth PLL for avoiding noise interference and DFE-less fast precharge sampling for over 10Gb/s/pin graphics DRAM interface

DRAM speed already reaches 7Gb/s/pin for GDDR interface [1,4]. As the bit rate increases, jitter of PLL, data-sampling margin, crosstalk and intersymbol interference (ISI) needs considerable management [1,3,5]. Moreover, as the supply voltage decreases, the self-generated internal noise of DRAM increases due to low efficiency of the internal voltage generator, especially the VPP voltage generator [2]. In general, the sensitivity of PLL to supply noise gives rise to large jitter accumulation. If the supply noise frequency is close to the PLL bandwidth, more jitter peaking occurs. Therefore, the PLL bandwidth is an important parameter to achieve low jitter performance [3]. Crosstalk becomes a crucial issue for over 7Gb/s GDDR interface [1]. However, the complexity of the transmitter and the CIO, capacitance of I/O, increase due to additional equalizers and pre- and de-emphasis drivers. For a compact transmitter, a low-overhead boosted transmitter is developed [4]. This paper presents an adaptive-bandwidth PLL in response to the supply and channel noises, a fast pre-charged data sampler without an additional decision-feedback equalizer (DFE), a crosstalk-induced-jitter-reduction technique and a compact transmitter with pre- and de-emphasis.