Topic: VCO-based Quantizers: Has Their Time Arrived? 

VCO-based quantizers take advantage of the steadily increasing speed of modern CMOS processes by quantizing time rather than amplitude. Their implementation leads to highly digital architectures that benefit directly from Moore's law, and offer intriguing benefits such as inherent shaping of their quantization noise. In this talk, we examine their potential for achieving high resolution analog-to-digital conversion (ADC), and identify key shortcomings such as nonlinearity of the voltage-to-frequency characteristic and its impact on SNDR. Circuit techniques are then presented to overcome such shortcomings, along with recent results verifying their effectiveness. In particular, we show that using phase rather than frequency within a continuous-time Sigma-Delta ADC topology enables 78dB SNDR performance within 20MHz bandwidth with a power efficiency of 330 fJ/conversion step. Finally, we conclude by generalizing the VCO-based quantizer as an efficient combination of a voltage-to-time converter and a time-to-digital converter, and discuss its advantages compared to other recent approaches which combine these components.