Ultra Low-Power Clocking Scheme Using Energy Recovery and Clock Gating

A significant fraction of the total power in highly synchronous systems is dissipated over clock networks. Hence, low-power clocking schemes are promising approaches for low-power design. We propose four novel energy recovery clocked flip-flops that enable energy recovery from the clock network, resulting in significant energy savings. The proposed flip-flops operate with a single-phase sinusoidal clock, which can be generated with high efficiency. In the TSMC 0.25-$mu$m CMOS technology, we implemented 1024 proposed energy recovery clocked flip-flops through an H-tree clock network driven by a resonant clock-generator to generate a sinusoidal clock. Simulation results show a power reduction of 90% on the clock-tree and total power savings of up to 83% as compared to the same implementation using the conventional square-wave clocking scheme and flip-flops. Using a sinusoidal clock signal for energy recovery prevents application of existing clock gating solutions. In this paper, we also propose clock gating solutions for energy recovery clocking. Applying our clock gating to the energy recovery clocked flip-flops reduces their power by more than 1000 $times$ in the idle mode with negligible power and delay overhead in the active mode. Finally, a test chip containing two pipelined multipliers one designed with conventional square wave clocked flip-flops and the other one with the proposed energy recovery clocked flip-flops is fabricated and measured. Based on measurement results, the energy recovery clocking scheme and flip-flops show a power reduction of 71% on the clock-tree and 39% on flip-flops, resulting in an overall power savings of 25% for the multiplier chip.      

A Low-Power Programmable DLL-Based Clock Generator With Wide-Range Antiharmonic Lock

A delay-locked-loop (DLL)-based clock generator for dynamic frequency scaling has been developed in a 0.13-${rm mu}hbox{m}$ CMOS technology. The proposed clock generator can generate a wide range of the multiplied clock signals ranging from 125 MHz to 2 GHz. In addition, owing to the proposed antiharmonic-lock block, the clock generator can change the frequency dynamically in one cycle time of the reference clock. The proposed DLL-based clock generator occupies 0.019 $hbox{mm}^{2}$ and consumes 21 mW at 2 GHz. The ratio of power consumption to frequency of the proposed clock generator is smaller than those of conventional ones.      

CMOS Differential Logic Family With Conditional Operation for Low-Power Application

In this paper, a set of CMOS differential logic circuits are introduced for use in low-power application. They perform a conditional operation for statistical power reduction during logic operation. The self-precharged version of the logic family provides additional power saving by allowing the use of a small-swing clock. Synchronous counters and bidirectional shift registers were designed in a 0.18-mum CMOS process technology to assess the performance of the proposed technique. The measurement results indicate that the counter with the proposed logic family achieves 50% power reduction compared with that of the conventional logic family. They also indicate that the shift registers with the proposed technique achieve 44%-63% power reduction at a typical switching activity of 0.25.     

Low-Power Successive Approximation Converter With 0.5 V Supply in 90 nm CMOS

We report on the design and characterization of an ultralow-power converter, designed for use in baseband digitization in wireless sensor network radio receivers. The converter uses a successive approximation architecture and operates robustly with a supply voltage as low as 450 mV, overcoming charge leakage limitations. Implemented in a 90 nm CMOS process, this design achieves a figure of merit of 0.14 pJ/Conv.Step for the converter core and shows the integration of a complete data-conversion subsystem, including reference generation, from a 0.5 V supply.     

Transmission Gates Combined With Level-Restoring CMOS Gates Reduce Glitches in Low-Power Low-Frequency Multipliers

Various 16-bit multiplier architectures are compared in terms of dissipated energy, propagation delay, energy-delay product (EDP), and area occupation, in view of low-power low-voltage signal processing for low-frequency applications. A novel practical approach has been set up to investigate and graphically represent the mechanisms of glitch generation and propagation. It is found that spurious activity is a major cause of energy dissipation in multipliers. Measurements point out that, because of its shorter full-adder chains, the Wallace multiplier dissipates less energy than other traditional array multipliers (8.2 mu W/MHz versus 9.6 mu W/MHz for 0.18mum CMOS technology at 0.75 V). The benefits of transistor sizing are also evaluated (Wallace including minimum-size transistors dissipates 6.2 muW/MHz). By combining transmission gates with static CMOS in a Wallace architecture, a new approach is proposed to improve the energy-efficiency further (4.7 muW/MHz), beyond recently published low-power architectures. The innovation consists in suppressing glitches via resistance-capacitance low-pass filtering, while preserving unaltered driving capabilities. The reduced number of V _dd-to-ground paths also contributes to a significant decrease of static consumption.     

Analysis and Design of Two Low-Power Ultra-Wideband CMOS Low-Noise Amplifiers With Out-Band Rejection

Two 3–5-GHz low-power ultra-wideband (UWB) low-noise amplifiers (LNAs) with out-band rejection function using 0.18- $mu{hbox{m}}$ CMOS technology are presented. Due to the Federal Communications Commission's stringent power-emission limitation at the transmitter, the received signal power in the UWB system is smaller than those of the close narrowband interferers such as the IEEE 802.11 a/b/g wireless local area network, and the 1.8-GHz digital cellular service/global system for mobile communications. Therefore, we proposed a wideband input network with out-band rejection capability to suppress the out-band properties for our first UWB LNA. Moreover, a feedback structure and dual-band notch filter with low-power active inductors will further attenuate the out-band interferers without deteriorating the input matching bandwidth in the second UWB LNA. The 55/48/45 dB maximum rejections at 1.8/2.4/5.2 GHz, a power gain of 15 dB, and 3.5-dB minimum noise figure can be measured while consuming a dc power of only 5 mW.      

The Design and Analysis of a CMOS Low-Power Large-Neighborhood CNN With Propagating Connections

The design of a large-neighborhood cellular nonlinear network (LN-CNN) with propagating connections is proposed. The propagating connections are utilized to achieve large-neighborhood templates in the shape of diamonds. Based on the propagating connections, each LN-CNN cell can only be connected to neighboring cells without interconnections to farther cells. Thus, it is suitable for very large scale integration implementation. The LN-CNN functions of diffusion, deblurring, and MÜller-Lyer illusion are successfully verified. Meanwhile, the functions of erosion and dilation are expanded with the diamond-shaped LN templates. Furthermore, the simple N- and P-type synapses stop all the static current paths so that the dc power dissipation can be reduced to only 0.7 mW on standby and 18 mW in operation. An experimental LN-CNN chip with a 20 $times$ 20 array has been fabricated using 0.18-$mu{rm m}$ CMOS technology. With the proposed LN-CNN chip, more applications and LN-CNN templates can be studied further.      

A Low-Power CMOS Linear-in-Decibel Variable Gain Amplifier With Programmable Bandwidth and Stable Group Delay

This brief presents a new circuit architecture for linear-in-decibel, constant-bandwidth variable gain amplifier (VGA). To obtain high linearity under low-voltage operation, this VGA is a closed-loop structure. In loop amplifier design, two techniques are applied: first, the loop amplifier is given finite input impedance. This arrangement keeps the VGA bandwidth constant under different gain setting. Second, a current-buffered compensation is applied for loop stability. Compared to the Miller compensation, this method achieves wider bandwidth. The prototype chip using 0.18-mum CMOS technology demonstrates that -10- to 20-dB gain and 0.5- to 30-MHz bandwidth can be programmed independently. The group delay difference within 30-dB gain control range is smaller than 1%. The total circuit dissipates 1.35 mA from a 1.8-V supply     

Embedded Measurement of GHz Digital Signals With Time Amplification in CMOS

This paper examines an embedded low-power technique for the single-shot measurement of GHz digital signals. Two circuits will be demonstrated; the first is a rise time measurement core, while the second represents an embedded technique for the characterization of narrow pulses. Both circuits can be seen as general tools to increase the low-end time dynamic range measurements of digital events in CMOS. The circuits rely on a new fast voltage-crossing detector to convert the input information and condition it into same polarity edges, separated by the timing information to be measured. Those edges are then in turn stretched further using time amplification, making them easily detectable with low-resolution time-to-digital converters. Dynamic current generation techniques are used in the front-end detector to greatly reduce the power consumption. The proposed circuits are compact and introduce only a few tens of femtofarads capacitive loading. The circuits were implemented in a standard 0.18-$mu$m CMOS process. Experimental results show the feasibility of the proposed approach. Rise times of 1 ns and pulses as narrow as 78 ps were successfully captured in a single-shot measurement approach, with total power dissipation not exceeding a few milliwatts, in each of the two cases.      

A Low-Power Fully Monolithic Subthreshold CMOS Receiver With Integrated LO Generation for 2.4 GHz Wireless PAN Applications

This paper reports a fully monolithic subthreshold CMOS receiver with integrated subthreshold quadrature LO chain for 2.4 GHz WPAN applications. Subthreshold operation, passive voltage boosting, and various low-power circuit techniques such as current reuse, stacking, and differential cross coupling have been combined to lower the total power consumption. The subthreshold receiver, consisting of the switched-gain low noise amplifier, the quadrature mixers, and the variable gain amplifiers, consumes only 1.4 mW of power and has a gain of 43 dB and a noise figure of 5 dB. The entire quadrature LO chain, including a stacked quadrature VCO and differential cross-coupled buffers, also operates in the subthreshold region and consumes a total power of 1.2 mW. The subthreshold receiver with integrated LO generation is implemented in a 0.18 mum CMOS process. The receiver has a 3-dB IF bandwidth of 95 MHz.     

CMOS Charge Pump With Transfer Blocking Technique for No Reversion Loss and Relaxed Clock Timing Restriction

A CMOS charge pump based on a transfer blocking technique and a modified precharge scheme is proposed for avoiding reversion loss and relaxing the timing restrictions imposed on input clocks. Comparison results in an 80-nm CMOS process indicate that, with no loading current, the output voltage of the proposed charge pump reaches almost 98% of the ideal boosting level with switching ripple reduced by up to 97%. They also indicate that output voltage deviations due to temperature and process variations are reduced by 24%–98% and 81%–95%, respectively.      

A 40 Gb/s CMOS Serial-Link Receiver With Adaptive Equalization and Clock/Data Recovery

This paper presents a 40 Gb/s serial-link receiver including an adaptive equalizer and a CDR circuit. A parallel-path equalizing filter is used to compensate the high-frequency loss in copper cables. The adaptation is performed by only varying the gain in the high-pass path, which allows a single loop for proper control and completely removes the RC filters used for separately extracting the high- and low-frequency contents of the signal. A full-rate bang-bang phase detector with only five latches is proposed in the following CDR circuit. Minimizing the number of latches saves the power consumption and the area occupied by inductors. The performance is also improved by avoiding complicated routing of high-frequency signals. The receiver is able to recover 40 Gb/s data passing through a 4 m cable with 10 dB loss at 20 GHz. For an input PRBS of 2 $^{7}-$1, the recovered clock jitter is 0.3 ps$_{rm rms}$ and 4.3 ps$_{rm pp}$. The retimed data exhibits 500 mV $_{rm pp}$ output swing and 9.6 ps$_{rm pp}$ jitter with ${hbox{BER}}≪ 10^{-12}$ . Fabricated in 90 nm CMOS technology, the receiver consumes 115 mW , of which 58 mW is dissipated in the equalizer and 57 mW in the CDR.      

A 45-nm Bulk CMOS Embedded SRAM With Improved Immunity Against Process and Temperature Variations

The variation tolerant assist circuits of an SRAM against process and temperature are proposed. Passive resistances are introduced to the read assist circuit with replica memory transistors to lower the wordline voltage accurately reflecting the process and temperature variations. For the sake of not only enlarging the write margin but also reducing power consumption and speed overhead, the divided dynamic power-line scheme based on a charge sharing is adopted. Test chips of 512-Kb SRAM macros and isolated memory cell TEGs are fabricated using 45-nm bulk CMOS technology. Two types of 6-T SRAM cells, whose sizes were 0.245 mum² and 0.327 mum² were designed and evaluated. From the measurement results, we achieved over 100-mV improvement for static noise margin, and 35 mV for write margin for both SRAM cells at 1.0-V worst condition by using assist circuitry. It enables the wordline level to keep higher voltage at the slowest condition than the typical process condition, which results in 83% improvement of the cell current compared with the conventional assist circuit. Furthermore, the minimum operating voltage in the worst case condition was improved by 170 mV, confirming a high immunity against process and temperature variations with less than 10% area overhead.     

A Highly Linear SAW-Less CMOS Receiver Using a Mixer With Embedded Tx Filtering for CDMA

An embedded filtering passive (EFP) mixer is used to overcome transmitter power leakage in a receiver without the use of a SAW filter. The receiver IC exhibits more than ${+}$ 60 dBm of Rx IIP$_{2}$ , 2.4 dB Rx noise figure, and ${+}$77 dB of Triple Beat (TB) with 45 MHz offset transmit leakage at 900 MHz Rx frequency while consuming only 18 mA from a 2.1 V supply. Thanks to the embedded filtering passive mixer, the proposed receiver IC shows an additional 15 dB Tx rejection compared to a conventional receiver. The additional Tx rejection improved the IIP $_{2}$ by 10 dB and TB by 30 dB. The complete receiver consists of a differential LNA employing an active post-distortion (APD), I/Q embedded filtering passive mixer, two TIAs for I/Q outputs. The fabricated receiver IC occupies 2.25 mm$^{2}$ including bonding pads, ESD devices, local oscillator (LO) input buffer, frequency divider, and mixer drivers. The receiver is fabricated using a 0.18 $mu$m CMOS process with 5 metal and 1 poly (5M1P) layer.      

A 90-nm CMOS Low-Power GSM/EDGE Multimedia-Enhanced Baseband Processor With 380-MHz ARM926 Core and Mixed-Signal Extensions

To meet the widely varying speed and power requirements of multifunctional mobile devices, an appropriate combination of technology features, circuit-level low-power techniques, and system architecture is implemented in a GSM/Edge baseband processor with multimedia and mixed-signal extensions. Power reduction techniques and performance requirements are derived from an analysis of relevant use cases and applications. The 44 mm² baseband processor is fabricated in a 90-nm low-power CMOS technology with triple-well option and dual-gate oxide core devices. The ARM926 core achieves a maximum clock frequency of 380 MHz at 1.4-V supply due to the usage of thin oxide (1.6 nm) devices. Power dissipation can be adapted to the performance requirements by means of combined voltage and frequency scaling to reduce active power consumption in medium-performance mode by 68%. To reduce leakage currents during standby mode, large SRAM blocks, nFET sleep transistors, and circuit components with relaxed performance requirements are implemented using devices with 2.2-nm gate oxide thickness     

A 1 MB Cache Subsystem Prototype With 1.8 ns Embedded DRAMs in 45 nm SOI CMOS

We describe a single voltage supply, 1 MB cache subsystem prototype that integrates 2 GHz embedded DRAM (eDRAM) macros with on-chip word-line voltage supply generation , a 4 Kb one-time-programmable read-only memory ( OTPROM ) for redundancy and repair control, on-chip OTPROM programming voltage generation, clock generation and distribution, array built-in self-test circuitry (ABIST), user logic and pervasive logic. The eDRAM employs a programmable pipeline, achieving 1.8 ns latency, and features concurrent refresh capability.      

A DLL-Based Programmable Clock Multiplier in 0.18-μ m CMOS With −70 dBc Reference Spur

This paper describes a 150-400 MHz programmable clock multiplier which uses a recirculating DLL. The clock multiplier uses a sampling phase detector and employs chopping, autozeroing and various other circuit techniques to reduce static phase offset and crosstalk between the reference and the output clock. The DLL is implemented in 0.18-mum CMOS, consumes 16 mW of power, and achieves 1-5 ps RMS jitter and -70 dBc reference spur level.     

A 1.25–5 GHz Clock Generator With High-Bandwidth Supply-Rejection Using a Regulated-Replica Regulator in 45-nm CMOS

A clock generator for high-speed chip-to-chip link receivers was implemented in a 45-nm CMOS SOI technology. A low sensitivity to supply voltage noise was achieved by means of a low-dropout voltage regulator using a replica feedback in the regulation loop, where the replica resistance is regulated by a second loop. We show that by adjusting the replica load the necessary matching of the $gm/gds$ ratio of the current sources can be achieved. A power supply rejection of $>,$22 dB was measured up to 1 GHz for a circuit operating from a 1 V supply with 80$~$ pF decoupling capacitance and a load current of 18.5 mA. The maximum supply sensitivity of the clock generation circuit (DLL plus phase rotators) was 4.5 ps/100 mV supply noise over the entire noise frequency range at clock frequencies from 1.25–5 GHz. The phase rotator achieves a wide range of operating frequencies by providing programmable rise/fall times in its selection stage. In addition, low voltage operation of the circuit was demonstrated at supply voltages down to 0.7$~$V and a clock frequency of 1.6 GHz.      

A Low-Power Single-Weight-Combiner 802.11abg SoC in 0.13 µm CMOS for Embedded Applications Utilizing An Area and Power Efficient Cartesian Phase Shifter and Mixer Circuit

A low-power 802.11abg SoC which achieves the best reported sensitivity as well as lowest reported power consumption and utilizes an extensive array of auto calibrations is reported. This SoC utilizes a two-antenna array receiver to build a single weight combiner (SWC) system. A new signal-path Cartesian phase generation and combination technique is proposed that shifts the RF signal in 22.5deg phase steps. A 3 dB improvement in received SNR is achieved in comparison to the single path receiver. The radio and AFE occupy 10 mm² of area in a digital 0.13 mum CMOS process of which 0.29 mm² is occupied by the SWC RF receiver. The radio+AFE consume 85 mW of power in active Rx mode of which 30 mW is utilized by the SWC RF front-end.