GENERAL DESCRIPTION

　　The ADS1204 is a four-channel， second-order，CMOS device with four delta-sigma （ΔΣ） modulators，designed for medium- to high-resolution A/D signal conversions from dc to 39kHz （filter response –3dB） if an oversampling ratio （OSR） of 64 is chosen. The output of the converter （OUTX） provides a stream of digital ones and zeros. The time average of this serial output is proportional to the analog input voltage

　　The modulator shifts the quantization noise to high frequencies. A low-pass digital filter should be used at the output of the ΔΣ modulator. The filter serves two functions. First， it filters out high-frequency noise.Second， the filter converts the 1-bit data stream at a high sampling rate into a higher-bit data word at a lower rate （decimation）