VCO-based analog-to-digital conversion
This dissertation presents a novel [delta sigma] analog-to-digital converter architecture which replaces the operational amplifier-based integrator with a pair of tunable oscillators. A switched-capacitor V-I converter is used to combine the input voltage with a feedback DAC output and convert it into a current for two pseudo-differential current-controlled oscillators. The oscillator outputs are counted with a digital counter, and a digital back-end [delta sigma] modulator is used to truncate the high-resolution counter outputs for the feedback DAC path. This architecture has compelling advantages in deep sub-micron and emerging technologies where supply voltages are decreasing to a point that traditional analog architectures are no longer feasible. Additionally, this architecture takes advantage of the increased speed in these short-channel technologies. Measured results on a 6.08mW prototype in TSMC 0.18um achieving 63.5dB in a 2MHz bandwidth are presented.