VCO-based quantizers take advantage of the steadily increasing speedof modern CMOS processes by quantizing time rather than amplitude.Their implementation leads to highly digital architectures thatbenefit directly from Moore's law, and offer intriguing benefits suchas inherent shaping of their quantization noise. In this talk, weexamine their potential for achieving high resolutionanalog-to-digital conversion (ADC), and identify key shortcomings suchas nonlinearity of the voltage-to-frequency characteristic and itsimpact on SNDR. Circuit techniques are then presented to overcome suchshortcomings, along with recent results verifying their effectiveness.In particular, we show that using phase rather than frequency within acontinuous-time Sigma-Delta ADC topology enables 78dB SNDR performancewithin 20MHz bandwidth with a power efficiency of 330 fJ/conversionstep. Finally, we conclude by generalizing the VCO-based quantizer asan efficient combination of a voltage-to-time converter and atime-to-digital converter, and discuss its advantages compared toother recent approaches which combine these components.
Wednesday, October 10, 2012
Free and open to the public