Effective number of bits

About: Effective number of bits is a research topic. Over the lifetime, 3776 publications have been published within this topic receiving 46130 citations.

A 20-mW 640-MHz CMOS continuous-time ΣΔ ADC with 20-MHz signal bandwidth, 80-dB dynamic range and 12-bit ENOB

Abstract: A wide bandwidth continuous-time sigma-delta ADC, operating between 20 and 40 MS/s output data rate, is imple- mented in 130-nm CMOS. The circuit is targeted for applications that demand high bandwidth, high resolution, and low power, such as wireless and wireline communications, medical imaging, video, and instrumentation. The third-order continuous-time mod- ulator comprises a third-order RC operational-amplifier-based loop filter and 4-bit internal quantizer operating at 640 MHz. A 400-fs rms jitter LC PLL with 450-kHz bandwidth is integrated, generating the low-jitter clock for the jitter-sensitive contin- uous-time ADC from a single-ended input clock between 13.5 and 40 MHz. To reduce clock jitter sensitivity, nonreturn-to-zero (NRZ) DAC pulse shaping is used. The excess loop delay is set to half the sampling period of the quantizer and the degradation of modulator stability due to excess loop delay is avoided with a new architecture. The ADC achieves 76-dB SNR, 78-dB THD, and a 74-dB SNDR or 12 ENOB over a 20-MHz signal band at an OSR of 16. The power consumption of the CT modulator itself is 20 mW and in total the ADC dissipates 58 mW from the 1.2-V supply. Index Terms—Analog-to-digital conversion, CMOS analog inte- grated circuits, continuous-time modulation, continuous-time filters, delta-sigma modulation, low-pass filter, low power design, low-voltage design, multibit internal quantization, sigma-delta modulation.

States encoding in multi-bit flash cells for optimizing error rate

Abstract: To store N bits of M≧2 logical pages, the bits are interleaved and the interleaved bits are programmed to ┌N/M┐ memory cells, M bits per cell. Preferably, the interleaving puts the same number of bits from each logical page into each bit-page of the ┌N/M┐ cells. When the bits are read from the cells, the bits are de-interleaved. The interleaving may be deterministic or random, and may be effected by software or by dedicated hardware.

A new class of asynchronous A/D converters based on time quantization

Abstract: This work is a contribution to a drastic change in standard signal processing chains. The main objective is to reduce the power consumption by one or two orders of magnitude. Integrated Smart Devices and Communicating Objects are application domains targeted by this work. In this context, we present a new class of Analog-to-Digital Converters (ADCs), based on an irregular sampling of the analog signal, and an asynchronous design. Because they are not conventional, a complete design methodology is presented. It determines their characteristics given the required effective number of bits and the analog signal properties. it is shown that our approach leads to a significant reduction in terms of hardware complexity and power consumption. A prototype has been designed for speech applications, using the STMicroelectronics 0.18-/spl mu/m CMOS technology. Electrical simulations prove that the factor of merit is increased by more than one order of magnitude compared to synchronous Nyquist ADCs.

A 0.16pJ/Conversion-Step 2.5mW 1.25GS/s 4b ADC in a 90nm Digital CMOS Process

Abstract: A high-speed 4b flash ADC in 90nm digital CMOS is presented that uses a dynamic offset-compensation scheme in its comparators. It achieves a sampling rate of 1.25GS/s with 3.7 ENOB (23.8dB SNDR) from dc to Nyquist while consuming 2.5mW. It has an energy per conversion step of 0.16pJ

Hybrid Architectures With Few-Bit ADC Receivers: Achievable Rates and Energy-Rate Tradeoffs

Abstract: Hybrid analog/digital architectures and receivers with low-resolution analog-to-digital converters (ADCs) are two low power solutions for wireless systems with large antenna arrays, such as millimeter wave and massive multiple-input multiple-output systems. Most prior work represents two extreme cases in which either a small number of radio frequency (RF) chains with full-resolution ADCs, or low-resolution ADC with a number of RF chains equal to the number of antennas is assumed. In this paper, a generalized hybrid architecture with a small number of RF chains and a finite number of ADC bits is proposed. For this architecture, achievable rates with channel inversion and singular value decomposition-based transmission methods are derived. Results show that the achievable rate is comparable to that obtained by full-precision ADC receivers at low and medium SNRs. A trade-off between the achievable rate and power consumption for the different numbers of bits and RF chains is devised. This enables us to draw some conclusions on the number of ADC bits needed to maximize the system energy efficiency. Numerical simulations show that coarse ADC quantization is optimal under various system configurations. This means that hybrid combining with coarse quantization achieves better energy-rate trade-off compared with both hybrid combining with full-resolutions ADCs and 1-bit ADC combining.