A fast-locking all-digital delay-locked loop for phase/delay generation in an FPGA

A fast-locking all-digital delay-locked loop(ADDLL) is proposed for the DDR SDRAM controller interface in a field programmable gate array(FPGA).The ADDLL performs a 90°phase-shift so that the data strobe(DQS) can enlarge the data valid window in order to minimize skew.In order to further reduce the locking time and to prevent the harmonic locking problem,a time-to-digital converter(TDC) is proposed.A duty cycle corrector(DCC) is also designed in the ADDLL to adjust the output duty cycle to 50%.The ADDLL,implemented in a commercial 0.13μm CMOS process,occupies a total of 0.017 mm~2 of active area.Measurement results show that the ADDLL has an operating frequency range of 75 to 350 MHz and a total delay resolution of 15 ps.The time interval error(TIE) of the proposed circuit is 60.7 ps.     

一种用于FPGA的快速锁定全数字延时锁定环的设计实现

本文提出了一种用于FPGA中DDR SDRAM控制器的接口快速锁定的全数字延时锁定环。该电路对数据选择脉冲(DQS)实现90度的相位偏移。为了实现延时锁定环的快速锁定,同时解决了错误锁定的问题,本文提出了一种新颖的数字时间转换器的结构。在延时环路中设计了占空比纠正电路,实现50％的占空比输出。该延时锁定环电路采用0.13μm标准CMOS工艺设计制作。测试结果表明,工作频率范围为75MHz～350MHz,数字控制延时链(DCDL)的调节精度为15ps,并且电路的闭环特性能跟踪电压、温度等环境的变化。     

A 250-MHz-2-GHz wide-range delay-locked loop

This paper describes a wide-range delay-locked loop (DLL) for a synchronous clocking which supports dynamic frequency scaling and dynamic voltage scaling. The DLL has wide operating range by using multiple phases from its delay line. A phase detector (PD) which combines linear and binary characteristics achieves low jitter and fast locking speed. A pulse reshaper makes output pulses of the phase detector have variable pulsewidth and variable voltage level to mitigate the static phase error due to the inherent mismatch of the charge pump. The DLL operates in the range from 250 MHz to 2 GHz. At 1 GHz operating frequency, RMS jitter and peak-to-peak jitter are 1.57 ps and 10.7 ps, respectively.     

基于FPGA的全数字延时锁相环的设计

针对传统模拟延时锁相环锁相精度不高、锁相速度慢、集成度低等问题,提出一种全数字延迟锁相环,采用电子设计自动化技术进行设计,并通过QuartusⅡ软件予以编辑与分析。仿真结果表明,该延时锁相环能够快速锁定,并能达到很高的精度,且可移植性强,适用于多种应用领域如微处理器、存储器与通用IC     

100 MHz all-digital delay-locked loop for low power application

An all-digital delay-locked loop (AD-DLL) is proposed for low power application. The AD-DLL saves design time and effort for synthesis. The number of transistors is reduced by 50%, by introducing a dual-clock dual-input data flip-flop and a coarse delay time buffer. The lock indicator enables zero jitter     

A wide-range delay-locked loop with a fixed latency of one clock cycle

A delay-locked loop (DLL) with wide-range operation and fixed latency of one clock cycle is proposed. This DLL uses a phase selection circuit and a start-controlled circuit to enlarge the operating frequency range and eliminate harmonic locking problems. Theoretically, the operating frequency range of the DLL can be from 1/(N/spl times/T/sub Dmax/) to 1/(3T/sub Dmin/), where T/sub Dmin/ and T/sub Dmax/ are the minimum and maximum delay of a delay cell, respectively, and N is the number of delay cells used in the delay line. Fabricated in a 0.35 /spl mu/m single-poly triple-metal CMOS process, the measurement results show that the proposed DLL can operate from 6 to 130 MHz, and the total delay time between input and output of this DLL is just one clock cycle. From the entire operating frequency range, the maximum rms jitter does not exceed 25 ps. The DLL occupies an active area of 880 /spl mu/m/spl times/515 /spl mu/m and consumes a maximum power of 132 mW at 130 MHz.     

A fast-locking PLL with all-digital locked-aid circuit

In this article, a fast-locking phase-locked loop (PLL) with an all-digital locked-aid circuit is proposed and analysed. The proposed topology is based on two tuning loops: frequency and phase detections. A frequency detection loop is used to accelerate frequency locking time, and a phase detection loop is used to adjust fine phase errors between the reference and feedback clocks. The proposed PLL circuit is designed based on the 0.35?µm CMOS process with a 3.3?V supply voltage. Experimental results show that the locking time of the proposed PLL achieves a 87.5% reduction from that of a PLL without the locked-aid circuit.     

A semidigital dual delay-locked loop

This paper describes a dual delay-locked loop architecture which achieves low jitter, unlimited (modulo 2π) phase shift, and large operating range. The architecture employs a core loop to generate coarsely spaced clocks, which are then used by a peripheral loop to generate the main system clock through phase interpolation. The design of an experimental prototype in a 0.8-μm CMOS technology is described. The prototype achieves an operating range of 80 kHz-400 MHz. At 250 MHz, its peak-to-peak jitter with quiescent supply is 68 ps, and its jitter supply sensitivity is 0.4 ps/mV     

An all-analog multiphase delay-locked loop using a replica delayline for wide-range operation and low-jitter performance

This paper describes an all-analog multiphase delay-locked loop (DLL) architecture that achieves both wide-range operation and low-jitter performance. A replica delay line is attached to a conventional DLL to fully utilize the frequency range of the voltage-controlled delay line. The proposed DLL keeps the same benefits of conventional DLLs such as good jitter performance and multiphase clock generation. The DLL incorporates dynamic phase detectors and triply controlled delay cells with cell-level duty-cycle correction capability to generate equally spaced eight-phase clocks. The chip has been fabricated using a 0.35-μm CMOS process. The peak-to peak jitter is less than 30 ps over the operating frequency range of 62.5-250 MHz, At 250 MHz, its jitter supply sensitivity is 0.11 ps/mV. It occupies smaller area (0.2 mm²) and dissipates less power (42 mW) than other wide-range DLL's [2]-[7]     

Resynchronising delay-locked loop

The delay-locked loop (DLL) is a device that is often used for PN-code tracking to synchronise direct sequence spread spectrum (DS-SS) systems. A DLL with resynchronising capability, which is more robust against loss of lock, is presented. The new scheme has two modes: a normal tracking mode and a resynchronising mode. The structure of the new loop and its function are described     

A power-efficient wide-range phase-locked loop

This work presents a phase-locked loop for clock generation that consists of a phase/frequency detector, charge pump, loop filter, range-programmable voltage-controlled ring oscillator, and programmable divider. The phase/frequency detector and charge pump are designed to reduce the dead zone and charge sharing for enhancing the locking performance, respectively. In the design of the range-programmable voltage-controlled oscillator, the original inverter ring of a delay line is divided into several smaller ones, and then they are recombined in parallel to each other. Programming the number of paralleled inverter rings allows us to generate the wide-range clock frequencies. This design shuts off some inverters that are not in use to reduce power consumption. To allow the phase-locked loop to shut off inverters, the feasibility of using controllable inverters by the output-switch and power-switch schemes is explored. Theoretical analyses indicate that power consumption of the voltage-controlled oscillator depends on transistors' sizes rather than operating frequencies. By applying the TSMC 0.35-μm CMOS technology, the proposed phase-locked loop that uses the power-switch scheme can yield clock signals ranging from 103 MHz to 1.02 GHz at a supply voltage of 1.8 V. Moreover, power dissipation that is proportional to the number of paralleled inverter rings is measured with 1.32 to 4.59 mW. The phase-locked loop proposed herein can be used in various digital systems, providing power-efficient and wide-range clock signals for task-oriented computations     

Multifrequency zero-jitter delay-locked loop

The approach of an all-digital phase locked loop is used in this delay-locked loop circuit. This design is designated to a system with two processing units, a master CPU and a slave system chip, that share the same bus. It allows maximum utilization of the bus, as the minimal skew between the clocks of the two components significantly reduces idle periods, and also set-up and hold times. Changes in the operating frequency are possible, without falling out of synchronization. Due to the special lead-lag phase detector, the jitter of the clock is zero, when the loop is locked, under any working conditions     

Reduced complexity delay-locked loop

In spread spectrum synchronisation the delay-locked loop (DLL) is widely used for PN-code tracking. A new DLL configuration using only one correlator to generate the timing error signal is presented. This reduces the hardware complexity of the code synchronisation. The structure of the new loop is described and performance results are shown     

A single-path pulsewidth control loop with a built-in delay-locked loop

A 1-1.27-GHz single-path pulse width control loop with a built-in delay-locked loop is presented. Based on the proposed circuit, not only can the 50% duty cycle of the output clock be assured but the phase alignment between the reference and output clocks can also be achieved. Moreover, the requirement of the reference clock with 50% duty cycle can be eliminated. By the single-to-complementary circuit and the switched charge pump, the duty cycle error can be reduced. Moreover, the duty cycle of the output clock can be adjusted for applications such as time-interleaved analog-to-digital converters, switched-capacitor circuits, and dc-dc converters. The proposed circuit has been fabricated in a 0.35-/spl mu/m CMOS process. The power consumption is 150 mW and the die area of the core circuit is 0.47/spl times/0.3 mm/sup 2/. The duty cycle of the output clock can be adjusted from 35% to 70% in steps of 5%.     

A differentially coherent delay-locked loop for spread-spectrumtracking receivers

A novel differentially coherent delay-locked loop (DCDLL) for accurate code tracking is proposed for direct sequence spread-spectrum systems. Due to the use of the differential decoder and exactly one correlator, the proposed scheme avoids the problems of gain imbalance. The tracking error variance is derived by linear analysis. When the proposed DCDLL scheme is applied in ranging with additive white Gaussian noise (AWGN) channel, the performance of the proposed DCDLL scheme is about 1.4 dB better than that of one-correlator tau-dither loop (TDL), and near that of the noncoherent DLL     

A dual-loop delay-locked loop using multiple voltage-controlleddelay lines

This paper describes a dual-loop delay-locked loop (DLL) which overcomes the problem of a limited delay range by using multiple voltage-controlled delay lines (VCDLs). A reference loop generates quadrature clocks, which are then delayed with controllable amounts by four VCDLs and multiplexed to generate the output clock in a main loop. This architecture enables the DLL to emulate the infinite-length VCDL with multiple finite-length VCDLs. The DLL incorporates a replica biasing circuit for low-jitter characteristics and a duty cycle corrector immune to prevalent process mismatches. A test chip has been fabricated using a 0.25-μm CMOS process. At 400 MHz, the peak-to-peak jitter with a quiet 2.5-V supply is 54 ps, and the supply-noise sensitivity is 0.32 ps/mV     

A fast locking and low jitter delay-locked loop using DHDL

A fast-locking and low-jitter delay-locked loop (DLL) using the digital-controlled half-replica delay line (DHDL) is presented. The DHDL can provide stable bias voltage for the charge-pump circuit to achieve low-jitter performances; meanwhile, the property of bandwidth tracking can still be preserved. It can also provide a larger pumping current to reduce the lock time in the initialization state and provide a smaller current to improve jitter performance in the locked state. For comparisons, both the proposed DLL and the self-biased DLL have been fabricated in a 0.35-/spl mu/m one-poly four-metal CMOS process. From the measurement results, the proposed DLL has a shorter lock time and a better jitter performance than the self-biased DLL. The root-mean-squared jitter and peak-to-peak jitter are less than 4.2 and 30 ps, respectively, occurring at 75 MHz, over an operating frequency range of 50-150 MHz.     

A high-resolution multi-phase delay-locked loop with offset locking technique

In this work, we propose a new type of high-resolution delay-locked loop (DLL) which achieves the performance of high-resolution output by offset locking techniques without restrictions of intrinsic delay in the delay cell. Compared to traditional multi-phase clock generator, this architecture has the features of small size, low jitters, low-power consumption and high resolution. This DLL has been fabricated in 0.35 μm complementary metal-oxide-semiconductor (CMOS) process. The measured root-mean-square and peak-to-peak jitters are 2.89 ps and 31.1 ps at 250 MHz, respectively. The power dissipation is 68 mW for a supply voltage of 3.3 V. The maximum resolution of this work is 144 p and the intrinsic delay of 0.35 μm CMOS process is 220 ps. Comparing with intrinsic delay, the improvement of maximum resolution is 34.5%.