A single OpAmp 2nd-Order ΔΣ ADC with a double integrating quantizer

Time-to-digital converters are an attractive topology for quantization because they rely on mostly digital blocks that benefit from scaling of transistors. Time-to-digital converters inherently need a time-domain input, but the input to analog-to-digital converters is primarily in the voltage-domain. Therefore, a voltage-to-time converter is necessary to use time-to-digital converters in analog-to-digital converters. Previously, circuit modifications have allowed voltage-to-time converters to provide an extra order of quantization noise shaping when used within a delta-sigma analog-to-digital converter. This work proposes another method that allows the voltage-to-time converter to function as an integrator. When combined with previous methods, this allows for an extra two orders of noise shaping to result from the quantizer.