Some embodiments include apparatus and methods using an integrator in a loop filter of a sigma-delta analog-to-digital converter (ADC), a digital-to-analog converter (DAC) located on a feedback path of the ADC, the DAC including output nodes coupled to input nodes of the integrator, and a comparator including input nodes to receive signals from output nodes of the integrator, and an output node to provide information during calibration of the DAC.