Designing Time-to-Digital Converter for Asynchronous ADCs

Time-to-digital converter designing and analysis for asynchronous ADCs is discussed in the paper. The proposed ADC utilizes two-level conversion scheme consisting in duty-cycle modulation and subsequent time-to-digital conversion (TDC). Three concepts of the asynchronous ADC digital serial output interface are presented. The comparison of minimum transmission rates of the serial output port(s) for each concept is carried out. Finally, the procedure of the evaluation of key ADC design parameters for the speech signal supporting a possible original input signal recovery is exemplified.