The present disclosure provides a converting module formed in a first die. The first die is coupled to a bus having a bus bit width. The converting module includes an analog-to-digital converter, configured to generate a first digital signal having a first bit width different from the bus bit width; and a sigma-delta modulator, coupled to the analog-to-digital converter, and configured to generate a second digital signal according to the first digital signal. The second digital signal has a bit width equal to the bus bit width. The sigma-delta modulator includes a filter and a quantizer. The number of bits outputted by the quantizer is equal to the bus bit width.