An asynchronous analog-to-digital converter (AADC) and a method of using the AADC are shown. The AADC includes a digital-to analog-converter (DAC), a continuous-time comparator that provides an output including a digital value of the DAC and a time value, and a first and a second continuous-time summer, each connected to receive an analog differential input on a first input, to receive a differential output of the DAC on a second input, and to provide a difference between the analog input and the output of the DAC to the continuous-time comparator and to an error estimator. The continuous-time comparator provides the output responsive to the difference between the analog input and the output of the DAC being zero.