Low Power Flash ADC Research Articles

Design of Wallace Tree Encoder for Flash ADC

Analog to digital converter plays a very important role in today’s digitized world as they have wide range of applications. Wallace tree encoder is an effective hardware implementation in VLSI circuits that is utilized for the analogue to digital conversion process. The Wallace tree encoder transforms thermometer code into binary code in an ADC. The suggested flash digital to analogue converter confirmed the energy, and speed. The proposed technique provides Less Delay, Less Power Consumption, and a lesser number of transistors compared to existing techniques. In this project, the proposed transmission gate full adder technique provide Less Delay, Less Power Consumption, Better Power Delay Product and a lesser number of transistors. The proposed encoder is made to count the 1s available to the logic gates for designing ROM encoders and fat tree conversion. The power may be conserved by building a low power, high performance Wallace tree encoder implementing transmission gate logic and modified full adders since Wallace tree encoder uses more power. The proposed system focuses at lowering the transistor count to improve power efficiency and delay comparator, and it is effective in minimizing the bubble errors. The Wallace tree encoder is designed by using transmission gate based full adder circuits. The proposed designs are designed and simulated using LTspice Tool with 45nm CMOS technology. The power consumption of the encoder circuit must be decreased in order to create a low power Flash ADC. The power consumption of this encoder changes noticeably when the internal full adder circuit is modified

Order Statistics Based Low-Power Flash ADC with On-Chip Comparator Selection

High-speed flash ADCs are useful in high-speed applications such as communication receivers. Due to offset voltage variation in the sub-micron processes, the power consumption and the area increase significantly to suppress variation. As an alternative to suppressing the variation, we have developed a flash ADC architecture that selects the comparators based on offset voltage ranking for reference generation. Specifically, with the order statistics as a basis, our method selects the minimum number of comparators to obtain equally spaced reference values. Because the proposed ADC utilizes offset voltages as references, no resistor ladder is required. We also developed a time-domain sorting mechanism for the offset voltages to achieve on-chip comparator selection. We first perform a detailed analysis of the order statistics based selection method and then design a 4-bit ADC in a commercial 65-nm process and perform transistor-level simulation. When using 127 comparators, INLs of 20 virtual chips are in the range of -0.34LSB/+0.29LSB to -0.83LSB/+0.74LSB, and DNLs are in the range of -0.33LSB/+0.24LSB to -0.77LSB/+1.18LSB at 1-GS/s operation. Our ADC achieves the SNDR of 20.9dB at Nyquist-frequency input and the power consumption of 0.84mW.

Mixed-mode Method Used for Pt100 Static Transfer Function Linearization

Abstract Pt100 is a resistance temperature detector characterized by a relatively linear resistance/temperature relationship in a narrow temperature range. However, the Pt100 sensor shows a certain degree of static transfer function nonlinearity of 4.42 % in the range between −200 °C and 850 °C, which is unacceptable for some applications. As a solution to this problem, a mixed-mode linearization method based on a special dual-stage piecewise linear ADC design is proposed in this paper. The first stage of the proposed dual-stage piecewise linear ADC is performed with a low-complex and low-power flash ADC of a novel sequential design. The novelty of the proposed sequential design is reflected in the fact that the number of employed comparators is equal to the flash ADC resolution. The second stage is performed with a delta-sigma ADC with a differential input and differential reference. Using the 6-bit flash ADC of novel design and the 24-bit delta-sigma ADC, the nonlinearity error is reduced to 2.6·10−3 %, in the range between −200 °C and 850 °C. Two more ranges are examined, and the following results are obtained: in the range between 0 °C and 500 °C, the nonlinearity error is reduced from 1.99 % to 5·10−4 %, while in the range between −50 °C and 150 °C, the nonlinearity error is reduced from 0.755 % to 2.15·10−4 %.

English

English

A Novel CNFET Technology Based 3 Bit Flash ADC for Low-Voltage High Speed SoC Application

The continuous scaling down of metal-oxide-semiconductor field effect transistors (MOSFETs) led to the considerable impact in the analog-digital mixed signal integrated circuit design for system-on-chips (SoCs) application. SoCs trends force ADCs to be integrated on the chip with other digital circuits. These trends present new challenges in ADC circuit design based on existing CMOS technology. In this paper, we have designed and analyzed a 3-bit high speed, low-voltage and low-power flash ADC at 32nm CNFET technology for SoC applications. The proposed ADC utilizes the Threshold Inverter Quantization (TIQ) technique that uses two cascaded carbon nanotube field effect transistor (CNFET) inverters as a comparator. The TIQ technique proposed has been developed for better implementation in SoC applications. The performance of the proposed ADC is studied using two different types of encoders such as ROM and Fat tree encoders. The proposed ADCs circuits are simulated using Synopsys HSPICE with standard 32nm CNFET model at 0.9 input supply voltage. The simulation results show that the proposed 3 bit TIQ technique based flash ADC with fat tree encoder operates up to 8 giga samples per second (GSPS) with 35.88µW power consumption. From the simulation results, we observed that the proposed TIQ flash ADC achieves high speed, small size, low power consumption, and low voltage operation compared to other low power CMOS technology based flash ADCs. The proposed method is sensitive to process, temperature and power supply voltage variations and their impact on the ADC performance is also investigated.

High-efficiency Low-power Flash ADC for High-speed Transceivers

High-efficiency Low-power Flash ADC for High-speed Transceivers