Power efficient high-speed DAC for wideband communication applications

This paper demonstrates a power efficient design of high-speed Digital-to-Analog Converters (DACs) for wideband communication systems. For Wireless personal area network applications with a 250 MHz signal bandwidth, a 6 bit DAC capable of two times the Nyquist rate sampling is implemented in a current steering segmented 2 + 4 architecture optimized for power efficiency. Along with a proposed master-slave deglitch circuit, several circuit techniques are investigated to improve dynamic performances such as linearity. Implemented in a 0.18 um CMOS process, our DAC achieved a superior conversion performance over the state-of-the-arts, exhibiting integral nonlinearity of less than 0.27 LSB and differential nonlinearity of less than 0.15 LSB. Measured spurious free dynamic range for 251 MHz output signal is 40.92 dB, with total power consumption at 1 GS/s of 6mW, yielding a figure-of-merits of 78.3 pJ/(conversion step*W).     

A 1-V CMOS D/A converter with multi-input floating-gate MOSFET

A low-voltage D/A converter using multi-input floating-gate MOSFET within a matrix current cell architecture is described in this paper. The two-input floating-gate p-channel MOSFET of each current cell performs the combined functions of current source and current switch. The double-gate-driven MOSFET circuit technique was employed in the digital circuitry to facilitate low supply voltage operation. A 6-bit and 8-bit digital-to-analog converter (DAC) have been fabricated in standard double-poly double-metal 1.2 μm CMOS technology. Measurements show a supply voltage as low as 0.9 and 1.0 V is sufficient to operate the 6-bit and 8-bit DAC, respectively, with a 5 Msamples/s conversion rate     

A 1.8-V 3.1 mW successive approximation ADC in system-on-chip

This paper describes a 10-bit 2.5 Msample/s successive approximation analog-to-digital converter (ADC) for SoC system. Based on conventional successive approximation ADC architecture a new and faster solution is used. The new solution consists of bootstrap switch, capacitors for sample-hold (S/H) circuit and DAC, using an offset cancellation method and there is no need for any active element. Together with an added bit and an offset compensation comparator the speed and accuracy is increased. The ADC exhibits higher 9 effective number of bits (ENOB) for sample rate to 2.5 Ms/s. The ADC consumes 3.1 mW from a 1.8 V supply and occupies about 0.25 mm². The measured SNR is 56.05 dB.     

An 8 bit, 100 kS/s,switch-capacitor DAC SAR ADC for RFID applications

An 8 bit switch-capacitor DAC successive approximation analog to digital converter (SAR-ADC) for sensor-RFID application is presented in this paper. To achieve minimum chip area, maximum simplicity is imposed on capacitive DAC; replacing capacitor bank with only a one switch-capacitor circuit. The regulated dynamic current mirror (RDCM) design is introduced to provide stabilized current. This invariable current from RDCM, charging or discharging the only capacitor in circuit is controlled by pulse width modulated signal to realize switch capacitor DAC. The switch control scheme is built using basic AND gates to generate the control signals for RDCM. Only one capacitor and reduced transistor count in digital part reduces the silicon area occupied by the ADC to only 0.0098 mm². The converter, designed in GPDK 90 nm CMOS, exhibits maximum sampling frequency of 100 kHz & consumes 6.75 µW at 1 V supply. Calculated signal to noise and distortion ratio (SNDR) at 1 V supply and 100 kS/s is 48.68 dB which relates to ENOB of 7.79 bits. The peak values of differential and integral nonlinearity are found to be +0.70/−0.89 LSB and +1.40/−0.10 LSB respectively. Evaluated figure of merit (FOM) is 3.87×10²⁰, which show that the proposed ADC acquires minimal silicon area and has sufficiently low power consumption compared to its counterparts in RFID applications.     

A 12-bit 0.35 μm CMOS area optimized current-steering hybrid DAC

In this paper a 12-bit current-steering hybrid DAC is implemented using AMS 0.35 μm CMOS process technology. The architecture and design methodology used for the implementation of the DAC offer advantages like design speed up, easiness in design and a small active area. The proposed hybrid DAC consists of four 3-bit parallel matched current-steering subDACs and resistive networks that properly weight the current output of each subDAC to obtain the overall voltage-mode output of the 12-bit hybrid DAC. The performance of the hybrid DAC is validated through static and dynamic performance metrics. Simulations indicate that the DAC has an accuracy of 12-bit and a SFDR higher than 66 dB in whole Nyquist frequency band. The simulated INL is better than 1 LSB, while simulated DNL is better than 0.25 LSB. At an update rate of 250 MS/s the SFDR for signals up to 10 MHz is higher than 66 dB. The Figure of Merit (FoM) of the implemented hybrid DAC is better than recently presented DACs with 12-bit resolutions and implemented using various process technologies. The proposed hybrid DAC supporting high update rates with good dynamic performance can be used as an alternative in various applications in industry including video, digital TV, cable modems etc.     

A low-Voltage 10-bit CMOS DAC in 0.01-mm/sup 2/ die area

A low-voltage 10-bit digital-to-analog converter (DAC) for static/dc operation is fabricated in a standard 0.18-/spl mu/m CMOS process. The DAC is optimized for large integrated circuit systems where possibly dozens of such DAC would be employed for the purpose of digitally controlled analog circuit calibration. The DAC occupies 110 /spl mu/m/spl times/94 /spl mu/m die area. A segmented R-2R architecture is used for the DAC core in order to maximize matching accuracy for a minimal use of die area. A pseudocommon centroid layout is introduced to overcome the layout restrictions of conventional common centroid techniques. A linear current mirror is proposed in order to achieve linear output current with reduced voltage headroom. The measured differential nonlinearity by integral nonlinearity (DNL/INL) is better than 0.7/0.75 LSB and 0.8/2 LSB for 1.8-V and 1.4-V power supplies, respectively. The DAC remains monotonic (|DNL|<1 LSB) as INL reaches 4 LSB down to 1.3-V operation. The DAC consumes 2.2 mA of current at all supply voltage settings.     

An ultra low noise readout integrated circuit for uncooled microbolometers

A low noise readout architecture for uncooled microbolometer focal plane arrays is described. The on-chip readout circuit contains an integration circuit in which the bolometer current is directed injected into a capacitor, and exhibits extremely low noise with no decrease in signal by using an ultra low noise capacitive transimpedance amplifier (CTIA). The simple configuration of the integration circuit makes it possible to operate more circuits in parallel, and increases the integration time and number of pixels. A 40 × 30 uncooled microbolometer focal plane array based on the low noise ROIC was implemented on silicon using a 0.5 μm CMOS technology. The total output noise voltage is 260 μV RMS. A noise at this level is so low that can loosen required TCR in the bolometer material. Experimental values of voltage responsivities of 3.98 × 10⁵ V/W on average at 1 Hz modulation frequency have been achieved.     

A 10-bit 200-MHz CMOS video DAC for HDTV applications

This paper describes a 10-bit 200-MHz CMOS current steering digital-to-analog converter (DAC) for HDTV applications. The proposed 10-bit DAC is composed of a unit decoded matrix for 6 MSBs and a binary weighted array for 4 LSB’s, considering linearity, power consumption, routing area, and glitch energy. A new switching scheme for the unit decoded matrix is developed to improve linearity further. Cascade current sources and differential switches with deglitch latch improve dynamic performance. The measured differential nonlinearity (DNL) and integral nonlinearity (INL) are 0.3 LSB and 0.2 LSB, respectively. The converter achieves a spurious-free dynamic range (SFDR) of above 55 dB over a100-MHz bandwidth and low glitch energy of 1.5 pVs. The circuit is fabricated in a 0.25 μm CMOS process and occupies 0.91 mm². When operating at 200 M Sample/s, it dissipates 82 mW from a 3.3 V power supply.     

A low power low area capacitor array based Digital to Analog Converter architecture

This paper presents a capacitor based Digital to Analog Converter architecture, which gives comparable performance with the conventional architecture with approximately half the total capacitance. The proposed architecture reduces the area and power dissipation in comparison with the conventional scheme. Further to these advantages, the proposed DAC architecture does not demand an additional reference voltage or an additional switching circuit. Closed form formulas to estimate the standard deviation of INL, DNL and the power consumption are derived. A comparison is also made between the standard architectures and the proposed architecture for the same unit capacitor, in addition to analyzing the capacitor parasitics and mismatches. These analytical comparisons are validated by simulating the proposed architecture and all the other conventional architectures for 10 bits with UMC 180 nm CMOS technology.     

An IEEE 802.11 and 802.16 WLAN Wireless Transmitter Baseband Architecture with a 1.2-V, 600-MS/s, 2.4-mW DAC

In this paper, we propose a transmitter baseband architecture for the present and up-coming WLAN applications (IEEE 802.11a/g, 802.11n, 802.16), based on a 600-MS/s current-steering DAC with a passive output load, to perform the baseband signal processing, avoiding the use of any active analog reconstruction filter. The DAC, fabricated in a 0.13-μm CMOS technology, consumes 2.4 mW from a 1.2-V single supply voltage. The DAC exhibits 68 dB of SFDR at full-scale for a 12-MHz input signal frequency and 9.7 bits of full-scale dynamic range in the bandwith from dc to 10 MHz.     

A 10-bit 300-MS/s asynchronous SAR ADC with strategy of optimizing settling time for capacitive DAC in 65 nm CMOS

A 10-bit 300-MS/s asynchronous SAR ADC in 65 nm CMOS is presented in this paper. To achieve low power, binary-weighed capacitive DAC is employed without any digital correction or calibration. Consequently, settling time for the capacitive DAC would be a dominant limiting factor for the ADC operating speed. A novel architecture is proposed to optimize the settling time for the capacitive DAC, which depends merely on the on-resistance of switches and the capacitance of unit capacitor and irrelevant to the resolution. Therefore, high-speed high-resolution SAR ADC is possible. What is deserved to highlight is that the architecture improves the ADC performance at a fraction of the cost, with only some capacitors and control logic added. Post-layout simulation has been made for the SAR ADC. At a 1.2-V supply voltage and a sampling rate of 300 MS/s, it consumes 1.27 mW and achieves an SNDR of 60 dB, an SFDR of 67.5 dB, with the Nyquist input. The SAR ADC occupies a core area of 450×380 μm².     

4-bit adder-accumulator at 41-GHz clock frequency in InP DHBT technology

A 41-GHz 4-b adder-accumulator test circuit implemented in InP double heterojunction bipolar transistor (DHBT) technology using 624 transistors is reported. High clock rates are obtained by combining the logic functions into pipelined latches. The adder-accumulator contains a single-level parallel-gated carry circuit that is used as a step toward reduced power consumption. The carry circuit has a maximum clock frequency of 55 GHz. The accumulator architecture employs modular, pipelined 2-b adders and is cascadable to 2 N-bits. The test circuit includes a 4-b digital to analog converter (DAC) that facilitates demonstration of high-speed operation.     

Spanning tree based algorithms for low latency and energy efficient data aggregation enhanced convergecast (DAC) in wireless sensor networks

Many wireless sensor networks (WSNs) employ battery-powered sensor nodes. Communication in such networks is very taxing on its scarce energy resources. Convergecast – process of routing data from many sources to a sink – is commonly performed operation in WSNs. Data aggregation is a frequently used energy-conversing technique in WSNs. The rationale is to reduce volume of communicated data by using in-network processing capability at sensor nodes. In this paper, we address the problem of performing the operation of data aggregation enhanced convergecast (DAC) in an energy and latency efficient manner. We assume that all the nodes in the network have a data item and there is an a priori known application dependent data compression factor (or compression factor), γ, that approximates the useful fraction of the total data collected.The paper first presents two DAC tree construction algorithms. One is a variant of the Minimum Spanning Tree (MST) algorithm and the other is a variant of the Single Source Shortest Path Spanning Tree (SPT) algorithm. These two algorithms serve as a motivation for our Combined algorithm (COM) which generalized the SPT and MST based algorithm. The COM algorithm tries to construct an energy optimal DAC tree for any fixed value of α (= 1 − γ), the data growth factor. The nodes of these trees are scheduled for collision-free communication using a channel allocation algorithm. To achieve low latency, these algorithms use the β-constraint, which puts a soft limit on the maximum number of children a node can have in a DAC tree. The DAC tree obtained from energy minimizing phase of tree construction algorithms is re-structured using the β-constraint (in the latency minimizing phase) to reduce latency (at the expense of increasing energy cost). The effectiveness of these algorithms is evaluated by using energy efficiency, latency and network lifetime as metrics. With these metrics, the algorithms’ performance is compared with an existing data aggregation technique. From the experimental results, for a given network density and data compression factor γ at intermediate nodes, one can choose an appropriate algorithm depending upon whether the primary goal is to minimize the latency or the energy consumption.     

分段式电流舵 D/A转换器抗di/dt噪声设计

设计了一个8位50MHzD/A转换器(DAC),采用5+3分段式电流舵差分输出结构,其中高5位采用温度计码方式译码,低3位采用二进制译码方式;从各电路模块设计结构上提高DAC抗di/dt噪声的能力;设计了一个低交叉点开关驱动电路,有效地降低了输出毛刺,减小了数字电路di/dt噪声的影响。采用VIS0.35μmCMOS工艺进行仿真,结果表明,微分非线性(DNL)和积分非线性(INL)均小于0.15LSB。     

A fully integrated low power PAM multi-channel UWB transmitter

A new transmitter for ultra-wideband (UWB) impulse radio is described in this paper. The new UWB transmitter implements a low power Gaussian shaping filter to reduce the side-lobe in the frequency domain. A simple pulse amplitude modulation (PAM) circuit is used to keep the power consumption low. The proposed architecture features the simple design, low-power operation, and enables the pulse-shape generation for a multi-channel UWB. The core layout size is only 0.2 mm². The simulation results show that the generated signals satisfy the FCC spectrum mask, and the average power consumption is <1.97 mW for the 1.8 V supply voltage. Pulses are transmitted at a PRF (pulse repetition frequency) of 40.5 MHz in 500 MHz bandwidth channels equally spaced within the 3.1–10.6 GHz UWB. This transmitter is designed and fabricated in a 0.18-μm CMOS process.     

基于微环谐振器的光学数模转换器

提出并实现了一种基于微环谐振器的2位光学数模转换器,该器件由2个微环谐振器和2个1×2光学分束器构成,该结构可以将一个2位电学数字信号转换成一个光学模拟信号。在SOI晶圆上制备出该光学数模转换器,采用热光效应调制微环谐振器。在输出端口得到光学模拟信号。通过静态光谱测试,确定微环谐振器的驱动电压和工作波长,最终展示了50ksamples/s的动态数模转换结果。     

1GS/s pipelined delta sigma modulator ADC using residue averaging technique

A two stage pipelined delta sigma modulator (PDSM) ADC is presented for broadband, high-resolution applications, which incorporate a first, order delta sigma modulator in each stage and combines the most significant bits of the first stage with the second stage output. A key feature of the PDSM ADC architecture is a SINC filter residue averaging technique, which results in mitigating the effect of track/hold and analog, subtract circuit errors, DAC non-linearity, and component mismatch. The input bandwidth of 62.5 MHz and the sampling frequency of 1 GHz result in an over sampling ratio of 8 for the first order modulators. MATLAB simulations for the two stage ADC show 13–15 bit resolution. A transistor level design in 0.18 um CMOS for the two stage ADC was captured with Cadence tools and simulations show 12 bit resolution with a 50 MHz input.     

An 8-bit low power DAC with re-used distributed binary cells architecture for reconfigurable transmitters

In this work an 8-bit DAC is presented which uses a new segmented architecture, where distributed binary cells are re-used in thermometric manner to realize the MSB unit cells. The DAC has been fabricated in 0.18 μm five-metal CMOS n-well process to be embedded in multi-standard reconfigurable wireless transmitters for low-speed applications. The proposed architecture has an inherent ability to reduce midcode glitch like the unary architecture, and the simulated midcode glitch is only 0.01 pV s. Simulation results show that the proposed DAC performs with an integral nonlinearity (INL) of 0.33 LSB and a differential nonlinearity (DNL) of 0.14 LSB. The DAC can achieve a maximum measured SFDR of 65.19 dB for 97.50 kHz signal at a sampling rate of 100 MSPS, without using any calibration or dynamic element matching (DEM) technique. For 1.07 MHz signal the measured SFDR is 56.84 dB at 100 MSPS sampling rate. At 50 MSPS sampling frequency and 146 kHz signal the SFDR of the DAC is 65.90 dB. The measured SFDR at 538 kHz signal is 63.62 dB for a sampling rate of 50 MSPS. Measured third order intermodulation distortion of the DAC is 58.55 dB, for a dual tone test with 1.03 MHz and 1.51 MHz signals at 50 MSPS sampling rate. Low power is also an important aspect in portable wireless devices. For 10.06 MHz signal and 100 MSPS sampling frequency, the power dissipation of the DAC is 20.74 mW with 1.8 V supply.     

An 8-bit, 10 kHz, 5.1 μW, 0.18 μm CMOS SAR ADC for RFID applications with sensing capabilities

An 5.1 μW, 1.8 V, 8-bit, successive approximation (SAR) analog-to-digital converter (ADC) using 10 kHz clock was designed and fabricated in a 0.18 μm CMOS technology for passive UHF radio frequency identification (RFID) applications. The ADC utilises a resistive digital to analog converter (DAC). The ADC can operate with low power consumption. The proposed comparator with cascode active load can offer large gain and can operate at a low supply voltage. The measured total power consumption is 5.1 μW at a 10 kHz input clock with a 1.8 V single supply, and 0.5 μW with 970 mV supply.     

Passive reference-sharing SAR ADC

Charge-redistribution successive approximation register (SAR) analog-to-digital converters (ADCs) are widely used for their simple architecture, inherent low-power consumption and small footprint. Several techniques aiming to reduce the power consumption, to increase the speed, and to reduce the capacitance spread have been developed, such as splitting the digital-to-analog converter (DAC) capacitor array, and charging and discharging the DAC capacitors in multiple steps. In this paper, a fully differential, low-power, passive reference voltage sharing SAR ADC architecture is presented, along with its theoretical analysis and test results. In this architecture, suitable for low sampling rate and low-resolution applications, the reference voltage is scaled down by successively connecting equally sized capacitors in parallel, allowing the use of small capacitor for its implementation. The implemented 6-bit ADC is one of the smallest ADCs reported in a 180-nm technology, and features a FoM between 30.8 and 39.3 fJ per conversion step without considering the clock generator power consumption.