A survey of high-speed high-resolution current steering DACs

Digital to analog converters(DAC)play an important role as a bridge connecting the analog world and the digital world.With the rapid development of wireless communication,wideband digital radar,and other emerging technologies,better performing high-speed high-resolution DACs are required.In those applications,signal bandwidth and high-frequency linearity often limited by data converters are the bottleneck of the system.This article reviews the state-of-the-art technologies of high-speed and high-resolution DACs reported in recent years.Comparisons are made between different architectures,circuit implementations and calibration techniques along with the figure of merit(FoM)results.

A 12-bit current steering DAC with 2-dimensional gradient-error tolerant switching scheme

A 12-bit intrinsic accuracy digital-to-analog converter integrated into standard digital 0.18μm CMOS technology is proposed. It is based on a current steering segmented 6＋6 architecture and requires no calibration. By dividing one most significant bit unary source into 16 elements located in 16 separated regions of the array, the linear gradient errors and quadratic errors can be averaged and eliminated effectively. A novel static performance testing method is proposed. The measured differential nonlinearity and integral nonlinearity are 0.42 and 0.39 least significant bit, respectively. For 12-bit resolution, the converter reaches an update rate of 100 MS/s. The chip operates from a single 1.8 V voltage supply, and the core die area is 0.28 mm^2.

A 10bit 2GHz CMOS D/A Converter for High-Speed System Applications

This paper presents a 2GS/s 10bit CMOS digital-to-analog converter （DAC） that consists of two unit current-cell matrixes for 6MSBs and 4LSBs, respectively, trading off between the precision and size of the chip. Current mode logic （CML） is used to ensure high speed,and a double centro-symmetric current matrix is designed by the Q^2 random walk strategy in order to ensure the linearity of the DAC. The DAC occupies 2.2mm × 2.2mm of die area and consumes 790mW with a single 3.3V power supply.

A direct digital frequency synthesizer with high-speed current-steering DAC

A high-speed SiGe BiCMOS direct digital frequency synthesizer（DDS）is presented.The design integrates a high-speed digital DDS core,a high-speed differential current-steering mode 10-bit D/A converter,a serial/parallel interface,and clock control logic.The DDS design is processed in 0.35μm SiGe BiCMOS standard process technology and worked at 1 GHz system frequency.The measured results show that the DDS is capable of generating a frequency-agile analog output sine wave up to 400＋MHz.

AN ANALYSIS OF RECURVATURE AND DECAY OF THE TROPICAL CYCLONE ‘MADI’(2013) OVER THE BAY OF BENGAL

The track of tropical cyclone‘Madi’showed almost 180° turn around,while immediately after recurvature it decayed rapidly in the following 24 hours.Sea surface temperature(SST)analyses rule out confrontation with low SST as cause of weakening.At 0000 UTC of 9 December 2013 diabatic heating(DH),potential vorticity(PV)and vertical wind shear(VWS)were favourable for intensification.However,a dry area close to the system centre at mid-troposphere subsequently engulfed the middle strata and the mid-tropospheric relative humidity(MTH)drastically reduced on 0000 UTC of 10 December 2013.The MTH further reduced on 0000 UTC of 11 December 2013.Lack of moisture in mid-troposphere apparently caused a mutation within the structure causing a sudden decrease in elevation.As the system dried up,reduction in convection above 400 h Pa hindered latent heat release.PV above 400 h Pa decreased significantly.Eventually,there was a spurt of VWS at 1200 UTC of the 10December 2013.The opposite wind flow between lower level and upper level whisked away the top of the system to northeast.Under the influence of the net northeasterly flow in lower to middle troposphere,the miniature vortex recurved southwestward and the vertical distortion due to shear weakened the system into a depression.