The AD9957 is one example of an Analog Devices DDS that incorporates an integrated digital inverse sinc filter. The plots shown here are from the AD9957 datasheet. The upper plot shows the sinc response (dashed line) and the frequency response of the inverse sinc filter. The lower trace shows the combined response of the inverse sinc filter and the DAC. Note the inclusion of the inverse sinc filter results in plus or minus 0.05dB flatness at the DAC output over the frequency band that extends from DC to 40% of the system clock frequency.