The WM8974 is a low power, mono codec with integrated support for a differential or single ended mic, and includes drivers for speakers or headphone, as well as the mono line output. Separate microphone and headphone amplifiers are not required, and advanced Delta-Sigma converters are used along with digital decimation and interpolation filters to give high quality audio at sample rates from 8 to 48 ks/s. Additional digital filtering options are available in the ADC path to provide application filtering such as 'wind noise reduction'. An advanced mixed-signal ALC function with noise gate also is provided. An on-chip PLL is provided to generate the required Master Clock from an external reference clock. The PLL clock can also be output if required elsewhere in the system. Different sections of the chip can also be powered down under software control by way of the selectable two or three wire control interface.