Abstract: An electric-power meter device includes a sensor which detects an electric energy and which outputs an analog signal with 50 Hz to 60 Hz, and a microcomputer which includes an analog-to-digital converter which, based on a delta-sigma modulation scheme, converts the input analog signal provided from the sensor to a digital signal based on a required sampling rate to output the digital signal, a central processing unit that performs data processing based on the digital signal converted by the analog-to-digital converter, and a timer unit that outputs a trigger signal in a cycle corresponding to the required sampling rate. The analog-to-digital converter includes a delta-sigma modulator and a decimation filter.

Abstract: To variably change the filter characteristic of a decimation filter in accordance with a sampling rate. A decimation filter 13 in a semiconductor device 1 sequentially inputs a signal sampled at a predetermined sampling rate fos, and calculates, for each input signal that is input within a predetermined period (a period for M+2N), a filter coefficient Cj for performing predetermined filtering processing in response to a trigger signal TR continuously applied, and furthermore sequentially multiplies the input signal by the calculated filter coefficient, accumulates a multiplication value within the predetermined period, and sequentially outputs the result. The predetermined period is made variable in accordance with a time interval at which the trigger signal is applied.

Abstract: To variably change the filter characteristic of a decimation filter in accordance with a sampling rate. A decimation filter 13 in a semiconductor device 1 sequentially inputs a signal sampled at a predetermined sampling rate fos, and calculates, for each input signal that is input within a predetermined period (a period for M+2N), a filter coefficient Cj for performing predetermined filtering processing in response to a trigger signal TR continuously applied, and furthermore sequentially multiplies the input signal by the calculated filter coefficient, accumulates a multiplication value within the predetermined period, and sequentially outputs the result. The predetermined period is made variable in accordance with a time interval at which the trigger signal is applied.