Highly linear VCO for use in VCO‐ADCs

Babaie-Fishani, Amir; Rombouts, Pieter

doi:10.1049/el.2015.3807

Cited by 69 publications

(78 citation statements)

References 7 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…This triggered an evolution from voltage-to time-domain based conversion techniques. A development in this evolution is the voltagecontrolled oscillator (VCO)-based A/D converter [1][2][3]. An important limitation of this VCO-based A/D conversion is the poor VCO linearity.…”

mentioning

confidence: 99%

See 1 more Smart Citation

Enhanced circuit for linear ring VCO‐ADCs

Borgmans

Rombouts

2019

Electron. lett.

Self Cite

View full text Add to dashboard Cite

Recently an extremely linear voltage-controlled ring-oscillator for use in VCO-ADCs was proposed by Babaie-Fishani and Rombouts. In this current Letter, a circuit-level technique to improve the bandwidth and noise performance of such a linear VCO is proposed. The key element is the modified delay cell, where the traditional cross-coupled inverters are modified into 'feed-forward' coupling inverters that pre-charge the subsequent elements in the ring. The resulting circuit maintains the excellent linearity, but has greatly enhanced bandwidth (up to 3 times higher) and considerably reduced power for the same circuit noise level (up to 2.5 times lower).

show abstract

mentioning

confidence: 99%

“…An important limitation of this VCO-based A/D conversion is the poor VCO linearity. In [1] a substantial improvement regarding this linearity issue was made by using a circuit-level optimisation approach. In this work, we propose a further improvement over this prior work in terms of power efficiency and speed.…”

mentioning

confidence: 99%

Enhanced circuit for linear ring VCO‐ADCs

Borgmans

Rombouts

2019

Electron. lett.

Self Cite

View full text Add to dashboard Cite

show abstract

“…We evaluate the performance with a fixed number of bit, OBG and OSR. As mentioned earlier, the non-linearity curve is estimated from the VCO reported in [13]. Fig.…”

Section: Example Designmentioning

confidence: 99%

Design challenges for a new mostly digital VCO‐based delta‐sigma modulator

Jamshidi

Maymandi-Nejad

2019

IET Circuits, Devices & Systems

View full text Add to dashboard Cite

This study presents an architecture and study of closed-loop continuous time delta-sigma modulation utilising only voltage-controlled oscillators (VCOs) and digital elements. It incorporates a VCO-based integrator in which the offset due to the carrier frequency (f c) is digitally subtracted. Unlike some prior structures, an extra VCO for reference signal generation is not necessary which can lead to a reduction in power consumption, area and noise. In addition, in comparison to a recently reported structure, the VCO is placed inside the feedback loop, so the input signal swing of the VCO is decreased and the linearity is improved. However, the proposed structure suffers from two noise folding effects at low frequencies which degrade the dynamic range of the modulator. These two noise folding effects will be analysed and it will be shown that these problems can be tackled by the right choice of f c and appropriate design. Behavioural simulations are done for the proposed structure to confirm the structure's performance.

show abstract

“…Introduction: VCO based analogue to digital conversion allows easy implementation of noise shaping A/D conversion [1][2][3][4][5][6]. However, in such a VCO ADC, the overall linearity will be limited by that of the VCO, which typically will not be good enough.…”

mentioning

confidence: 99%

Design of a low‐voltage op‐amp‐less ASDM to linearise VCO‐ADC

Babaie-Fishani

Rombouts

2016

Electron. lett.

Self Cite

View full text Add to dashboard Cite

The actual version was published as [1]. REFERENCES[1] A. Babaie-Fishani and P. Rombouts, "Design of a low-voltage op-amp-less ASDM to linearise VCO-ADC," Electron. Lett., vol. 52, no. 11, pp. 911-913, 2016. Design of a low-voltage op-amp-less ASDM to linearise VCO-ADCAmir Babaie-Fishani, and Pieter Rombouts,We present a very simple ASDM design for linearization of VCO ADC's. The circuit only consists of a passive feedback filter and a schmitt trigger. By proper sizing, the nonlinearity error can be reduced to well below 0.12% for input signals that go almost rail-to-rail. The design has been manufactured in the low power version of TSMC 65nm technology and was measured at a 1V power supply.Introduction: VCO based Analog to Digital conversion allows easy implementation of noise shaping A/D conversion [1][2][3][4][5][6]. However, in a straightforward implementation of such a VCO ADC, the overall linearity will be limited by the linearity of the VCO, which typically will not be good enough. A potential solution is to convert the input voltage into a two-level signal where the information is stored in the duty cycle of the resulting square-wave using an Asynchronous Sigma Delta Modulator (ASDM) or a Pulse Width Modulator (PWM). This method is known as . Untill now all reported implementations either require an op-amp, a highly linear ramp source, or a linear gm cell [5][6][7]. In practice such high-performance analog circuits are difficult to implement at today's low supply voltages (of the order of 1 Volt) and hence are to be avoided. An alternative would be an ASDM with a passive RC loop filter [4,8,9]. However, it is not obvious how such a passive ASDM should be designed as to achieve simultaneously high bandwidth and good good linearity. For this reason, untill now, such a circuit has not yet been demonstrated in practice. In this letter, we explain how such a passive ASDM linearization of a VCO can be designed to achieve good overall performance. The validity is confirmed by measurements on a protoype implemented in a 65nm technology.

show abstract

Highly linear VCO for use in VCO‐ADCs

Cited by 69 publications

References 7 publications

Enhanced circuit for linear ring VCO‐ADCs

Enhanced circuit for linear ring VCO‐ADCs

Design challenges for a new mostly digital VCO‐based delta‐sigma modulator

Design of a low‐voltage op‐amp‐less ASDM to linearise VCO‐ADC

Contact Info

Product

Resources

About