采用双R-2R电阻网络结构的12位电压型D/A转换器

介绍了采用双R-2R电阻网络结构实现12位电压输出型D/A转换器的设计及激光修调方案.重点分析了运放失调电压对双R-2R电阻网络结构D/A转换器线性误差的影响,并与其他常见的实现双极性电压输出的R-2R电阻网络结构进行比较,给出了理论估计和仿真结果.采用双R-2R电阻网络实现的12位D/A转换器芯片(不包括运放)在带CrSi电阻的8μm CMOS工艺上流片和修调测试.电阻网络芯片和运放芯片采用厚膜混合工艺组装,实现电压输出D/A转换器功能.测试结果显示,设计的电路达到了预期目标.     

一种新颖的R-2R电阻网络

设计了一种新颖的“5+7”分段式结构的R-2R电阻网络。与典型12位R-2R电阻型D/A转换器相比,采用该电阻网络的12位D/A转换器所需并联的MOS开关管数量大为减少,约为前者的1/8,提高了MOS开关管的匹配性。基于2 μm SOI CMOS工艺,采用该R-2R电阻网络结构设计了一款±15 V电压供电、双基准、12位四通道的D/A转换器,修调后,该D/A转换器DNL和INL典型值分别为0.15 LSB和0.27 LSB。     

16位逐次逼近A/D转换器熔丝误差修调技术

提出了一种提高16位逐次逼近(SAR)A/D转换器精度的熔丝误差修调技术。该技术用于提高A/D转换器内部核心模块—16位DAC的精度,从而达到提高整个A/D转换器精度的目的。电路采用标准CMOS工艺流片。测试结果显示,熔丝误差修调后,常温下,电路的INL为2.5 LSB,SNR为88.8 dB,零点误差EZ为1.1 LSB;修调后,A/D转换器有效位数ENOB从12.56位提高到14.46位。     

采用熔丝修调技术的高精度电流舵D/A转换器

高精度D/A转换器的实际精度往往低于理论上的精度。针对这个长期困扰的难题,在设计16位D/A转换器的过程中,提出了一种熔丝修调技术,即通过修调电流源输出端的电流,有效地减小电流源失配和有限输出阻抗对D/A转换器的DNL和INL的影响,大幅度提高D/A转换器的精度。基于0.18 μm CMOS 工艺的测试结果表明:在采用熔丝修调技术前,该电路的DNL和INL分别为－0.72~9.07 LSB和－5.55~18.1 LSB;在采用熔丝修调技术后,该电路的DNL和INL分别为－3.95~0.70 LSB和1.94~8.06 LSB。当输入信号频率为102 MHz、采样频率为500 MHz时,SFDR达到82.16 dBc,完全满足D/A转换器高精度的要求。     

一种带双极性基准的双R-2R电阻网络结构

介绍了一种带双极性基准(±10 V)的双R-2R电阻网络结构。该结构充分利用双极性基准的优势,减少了双极性输出所需运算放大器的数量,提高了D/A转换器的精度;同时又降低了电路对工艺绝对精度的要求。经过理论推算和电路模拟仿真,在相同工艺精度条件下,采用该结构的12位D/A转换器,其精度优于其他两种采用常规双极性输出结构的D/A转换器。     

一种电流型10位D／A转换器

本文介绍了１０位Ｄ／Ａ转换器ＳＤＡ１００的电路结构和工作原理，重点叙述了工艺制作技术以及电路中ＣｒＳｉ薄膜电阻的激光修调技术，并介绍了一些实际制作经验，为以后的设计提供参考。     

ROS高精度Cr-Si薄膜电阻网络及其应用

硅上高精度薄膜电阻(ROS)不仅是一种新型的混合集成电路电阻元件,而且,由于其工艺能与双极型和CMOS工艺相兼容,因而也是单片集成电路中高精度电阻网络制作的理想技术.本文介绍了ROS工艺及其在12位硅栅CMOS D/A转换器中的应用.     

激光修调对CrSi薄膜电阻稳定性的影响

该文分析了激光修调对CrSi薄膜电阻稳定性的影响,获得了对CrSi薄膜电阻进行激光修调的优化方法.实验结果表明,150 ℃储存48 h,可完全消除激光修调带来的影响,使CrSi薄膜电阻温度系数降到了20×10-6/℃,提高了CrSi薄膜电阻网络的稳定性,从而为研制高性能模拟集成电路打下坚实的基础.     

电压型R-2R梯形网络DAC线性误差分析方法

根据节点电阻模型和分析方法,设计了一个12位电压型R-2R梯形网络D/A转换器(DAC)。仿真结果表明,该D/A转换器的积分线性误差(INL)可低至0.21 LSB;该模型和分析方法能够有效地估计和用于减小由R-2R梯形网络各电阻之间的差值导致的DAC线性误差。     

一种12位D/A转换器的技术研究

介绍了一种12位带内基准的电压输出型D/A转换器的电路实现原理、线路设计及其制作工艺特点.通过采用优化设计的R-2R电阻开关网络、温度补偿齐纳基准源和带JFET输入级的输出运算放大器等模拟电路单元,基于一种P阱5 μm LC2MOS工艺,研制出该12位D/A转换器.它具有转换精度高、线性及微分误差小、功耗低、转换速度快、使用方便等优点.     

An inherently monotonic 12 bit DAC

Describes a 12 bit DAC which uses diffused resistors and requires no trimming to guarantee monotonicity for all grades over the temperature range. The segmented ladder design, departing from the traditional R-2R approach used in virtually all high-speed high resolution converters, provides inherent monotonicity and differential linearity as high as 13 bits. Also afforded is a more uniform step size over the temperature range than the trimmed 12 bit converters. The only critical resistor matching occurs at the major carries or midpoints of each of the eight segments and the tolerances are equivalent to that of a 9 bit DAC, or eight times lower than the R-2H approach. In essence, the problem has been divided into eight separate problems, each with tolerances eight times lower than that of a 12 bit DAC. The converter has been found to be immune to variations in temperature, time, process, and mechanical stress. The circuit also features differential high compliance current outputs, wide supply range, and a multiplying input.     

A no-trimming SLIC two-chip set with coin telephone signalingfacilities

A subscriber line interface circuit (SLIC) two-chip set that eliminates off-chip functional trimming and integrates coin telephone set facilities as well as BORSCHT functions is described. The LSI chip set consists of (a) a subscriber interface IC fabricated using a 320-V dielectrically isolated bipolar process with on-chip thin-film resistors and double-layer metal, and (b) a subscriber processor IC with oversampling A-D/D-A converters and a microprogrammable digital signal processor (DSP), using a 1.6-μm CMOS process. Chip sizes are 5.5 mm×6.06 mm and 6.0 mm×5.7 mm, respectively. Using the two-chip set, an SLIC for a coin telephone set can be designed without using high-precision filter components or hybrid ICs with functional trimming     

Calculation of the resistance value of laser-trimmable planar resistors in an interactive mask-layout design system

The calculation method is especially suited for diffused resistors in integration processes and metal-film resistors in thin-film processes which can be adjusted by laser trimming. The method is based on a special application of Green's boundary formula. By modeling the resistor in a special way, the potential problem is reduced to a single-boundary problem. As a consequence, the calculation time and the necessary computer memory are reduced while the accuracy reduction remains small in practical cases. Therefore, the calculation can be carried out on a small computer, making interactive computer design of laser-trimmable resistors on IC layouts more feasible and less expensive. The computing time typically amounts to a few seconds. The method is illustrated by practical examples.     

Stability of miniaturized non-trimmed thick- and thin-film resistors

This paper is focused on reliability tests of non-trimmed miniaturized thin-film and thick-film resistors. Thick-film resistors are screen printed by polymer paste on LTCC (Low Temperature Co-fired Ceramic) substrate by two different approaches. Nonstandard precise screen printing process provide tolerance of resistivity less than 5% and thus further trimming is not necessary. OhmegaPly material with Nickel Phosphorous (NiP) metal alloy is used for thin-film resistors fabricated by subtractive process. Miniaturized resistors have dimensions 0.5 × 0.5 mm, and thus 1 square, with thickness 1 μm for thin-film and 20 μm for thick-film resistors. Stability of miniaturized resistors were tested by humidity test, thermal shocks, long-term thermal ageing, direct current stress, current pulses and simulation of soldering process using VPS (Vapour Phase Soldering). Resistivity of resistors is measured by four wire method before and after each set of test and relative change of resistivity is plotted in graphs. Influence of every test on each type of resistor is analysed.     

一种四象限14位乘法型D/A转换器设计

设计了一种14位乘法型D/A转换器。采用高3位温度计编码、低11位二进制编码的分段电流模R-2R电阻网络结构,规避了高分辨率二进制电流模R-2R电阻网络开关尺寸大、版图匹配难度大的缺点。基于混合信号CMOS工艺进行了流片,实测DNL在±0.5 LSB以内,INL在±0.8 LSB以内。该D/A转换器适用于工业控制、仪器仪表等领域。     

A finite-mesh technique for laser trimming of thin-film resistors

A laser trimming technique in which a finite number of links are cut in a regular mesh of identical-valued resistors is described. The method eliminates long-term resistance drift due to slow annealing in the `heat-affected-zone' adjacent to the laser kerf. It is shown that the precision and resolution can be comparable to those achieved with conventional methods, and that quite wide ranges (up to 4:1) of absolute values can be obtained with small meshes. A computational method for constructing a lookup table of resistor values for different cut patterns is described     

Polysilicon resistor trimming by laser link making

A technique for laser trimming of polysilicon resistors has been developed. In this scheme an undoped polysilicon film is patterned lithographically, and then photoresist patterns are used to prevent doping of certain narrow areas of each resistor during the impurity implant; thus, the protected areas remain insulating after wafer processing. Subsequent laser scanning of the undoped regions can produce precise reductions in resistance by lateral diffusion of dopant impurities. Trimming can be accomplished by changing either the laser power or the position. Q-switched Nd:YAG (1.06-μm wavelength) and second-harmonic (0.53-μm wavelength) radiations have produced successful results. The process was applied to passivated resistors with negligible (perhaps zero) post-trim drift, and the temperature coefficients of resistivity (TCRs) of trimmed resistors can be matched to the TCRs of untrimmed resistors in the same film     

Reducing photoelectric response when functionally trimming with lasers

A laser processing technology has been developed that dramatically reduces, or virtually eliminates, laser-induced performance shift of a device during functional trimming. While functional laser trimming of monolithic integrated circuits and thick-film hybrid circuits has been used for over 20 years to improve yields and device performance, photoelectric response in the silicon itself to the conventional wavelengths created long delays in processing and even circuit latch-up. The answer to these problems turned out to be an alternative laser wavelength which is absorbed well by both thin-film and thick-film resistor materials but is "invisible" to silicon-based structures. This paper describes the results obtained by using the 1.3-/spl mu/m wavelength of a diode-pumped Nd:YLF laser for trimming deposited, thin-film-on-silicon integrated circuits and the 1.3-/spl mu/m wavelength of Nd:YAG laser for screen-printed, thick-film hybrid circuits. The trimming, or "tuning" of thin-film-on-silicon circuits with a low-power version of the alternative wavelength has permitted both the shrinking of resistor geometries and the expansion of the types of circuits that can be functionally tuned. Secondly, the advent of higher laser power output of the same wavelength has eliminated the photoelectric response problems associated with functionally laser trimming hybrid and multichip module circuits that incorporate silicon devices in their construction. Results are given from actual production devices.     

A complete high-speed voltage output 16-bit monolithic DAC

A new single-chip 16-bit monolithic digital/analog converter (DAC) with on-chip voltage reference and operational amplifiers has achieved /spl plusmn/0.0015% linearity, 10 ppm//spl deg/C gain drift, and 4-/spl mu/s settling time. Novel elements of the 16-bit DAC include: the fast settling open-loop reference with a buried Zener, a fast-settling output operational amplifier without the use of feedforward compensation, and a modified R-2R ladder network. Thermal considerations played a significant role in the design. The DAC is fabricated using a 20-V process to reduce device sizes and therefore die size. All laser trimming including temperature drift compensation is performed at the wafer level. The converter does not require external components for operation.