SENSORS

ACOUSTICInterfacing WM72xxDigital MicrophonesProduct OverviewWolfson’s WM72xx DMIC (Digital Microphone) offers bestin-class,low noise performance with PDM (Pulse DensityModulation) output. As the digital interface provides directconnection to the CODECs digital domain, the DMIC requiresless external components and PCB area. This provides asimplified interface connection and gives a higher robustnessto system noise interference compared to an analogmicrophone interface.Stereo Digital Microphone InterfaceThe output characteristic of the DMIC enables the outputof two microphones to be connected together in a stereoconfiguration (as shown below). The data from onemicrophone is interleaved with the data from the other.ACOUSTICWolfson provides a wide range of audio CODECs with singleor multiple DMIC input interfaces. Connectivity is achievedusing a simple 2 wire CLK and DATA interface. As eachDMIC interface supports up to 2 microphones, the DMICinterface is more flexible and makes it easier to implementadditional microphones to support stereo recording, ambientnoise cancellation, microphone array or beam formingfeatures into single DMIC voice recording applications.Further information on system solutions with Wolfson’sCODECs and Microphones is available in WAN_0225.16Mono Digital Microphone InterfaceMono Digital Microphone Interface shows the mono DMICinterface connection to the CODEC. The PDM DAT (Data)outputs data on the rising or falling edges of the incomingCLK (Clock) signal based on the LRSEL pin. The DAT outputis high impedance when not outputting data at the otheredges. Therefore it is recommended to turn on the selectedADC channel according to LRSEL pin to avoid the CODECsampling at the high impedance output.The left channel is transmitted following the rising CLKedge when LRSEL = 1. Therefore the left channel should besampled by the CODEC on the falling edge. Similarly whenLRSEL = 0, the DMIC is set as right channel. In this case, theright channel DMIC is sampled by the CODEC on the risingCLK edge. The output data on the stereo DMIC configurationis summarized in the above figure on Output Data on StereoDMIC Configuration.The DMIC interface offers seamless integration with WolfsonCODECs. With the design consideration as discussedhere, the system designer can take full advantage of theWolfson DMIC to meet the most demanding acoustic designchallenges in the system application.www.FutureElectronics.com/Sensors