A conversion circuit that performs analog-to-digital conversion is described. During operation, the conversion circuit receives an input signal. Then, the conversion circuit performs analog-to-digital conversion and provides a quantized output corresponding to the input signal based at least in part on a first power-supply voltage and a second power-supply voltage of the conversion circuit. For example, the quantized output may be based at least in part on a comparison of the input signal to the first power-supply voltage and the second power-supply voltage. Moreover, the first power-supply voltage and the second power-supply voltage may specify a full-scale range of the conversion circuit. When the full-scale range exceeds a second full-scale range associated with reference voltages that are other than the first power-supply voltage and the second power-supply voltage, the quantized output may correspond to a larger number of bits than when the full-scale range equals the second full-scale range.