A delta-sigma analog-to-digital converter (ΔΣ ADC) has a delta-sigma modulator, a decimation filter and an error suppression circuit. The delta-sigma modulator receives an analog input, and converts the analog input into a first digital output. The decimation filter is coupled to the delta-sigma modulator, and generates a second digital output according to the first digital output. The error suppression circuit is coupled to the decimation filter, and receives an error input and injects an error output into the second digital output according to the error input.