Time-domain approach for analog circuits in deep sub-micron LSI

Abstract

As the scaling of LSI is going to extremely fine regions toward the ultimate feature size, one of difficulties faced in analog circuit design is reduction of the dynamic range (DR) due to the supply voltage reduction. Unlike digital circuits, where the noise margin for logic operation is the key criterion, analog circuits need an enough DR. The reduced supply voltage directly results in DR degradation of the conventional analog circuits in the voltage-domain. Especially in mixed-signal LSIs, supply voltage instability, caused by logic operation, tends to degrade DR further. In this paper, we will first discuss potential capability of a new paradigm of time-domain circuits by comparing with the conventional voltage/current-domain circuits in terms of DR and power consumption. Next, as basic circuit components for the time-domain approach, current status of TDA (Time-Difference Amplifier) and TDC (Time-to-Digital Converter) will be reviewed. Finally, some application examples of the time-domain circuits are introduced to demonstrate the feasibility of the time-domain approach.

A Successive Approximation Time-to-Digital Converter with Single Set of Delay Lines for Time Interval Measurements

“…Time-to-digital converters are devices that convert time domain information into a digital representation [ 1 , 2 , 3 , 4 , 10 , 11 , 12 , 13 ], so they act as analog-to-digital converters for time-mode signal processing systems. Thus, TDCs are an enabler for the time-domain digital processing of continuous signals.…”

“…The TDCs have been originally developed for precise time interval measurements in space science and high-energy physics in the 80 s [ 13 , 14 ]. With the improved time resolution TDCs have been widely used in time-of-flight measurement applications [ 15 , 16 , 17 , 18 , 19 , 20 ], for example in laser range finders [ 1 , 2 , 12 ].…”

“…Nowadays, the time-to-digital converters find a broad spectrum of applications such as digital storage oscillators, laser-based vehicle navigation systems, medical imaging and instrumentation, infinite and finite impulse response filters, all digital phase-locked loops, clock data recovery, and channel select filters for software-defined radio [ 1 , 2 , 10 , 12 , 13 ]. In consumer electronics, the first common application of TDC was its use as a phase detector in ADPLLs [ 3 , 9 , 11 ].…”

“…In consumer electronics, the first common application of TDC was its use as a phase detector in ADPLLs [ 3 , 9 , 11 ]. This application has triggered extensive research on TDCs, especially in the field of on-chip frequency synthesizers, and resulted in a development of new conversion algorithms, architectures, and implementations to improve their performance in terms of time resolution, conversion speed, and power [ 12 ]. Various types of TDC architectures have been proposed to address these objectives.…”

“…By analogy to analog-to-digital converters, they can be classified into Nyquist-rate TDCs and oversampled TDCs [ 16 ]. Nyquist-rate TDCs include counter TDCs, delay line and Vernier line TDCs [ 10 , 12 , 21 ], TDCs with interpolation, pulse-shrinking or pulsestretching, successive approximation TDCs [ 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 , 36 , 37 ], flash and pipelined TDCs [ 1 , 2 ]. Noise-shaping TDCs are aimed to suppress the quantization noise using system-level techniques such as Sigma-Delta modulation by moving most of in-band quantization noise outside the signal band in order to achieve a large signal-to-noise ratio (SNR) and improve effective TDC resolution.…”