DocID023777 Rev 2

7/19

AN4184

Schematic hints

19

3

Schematic hints

Digital microphones frequently operate in an environment where a codec provides the

suitable clock and consequently accepts the digital data of the microphone. Figure 7 below

depicts the two typical connections, part (a) shows the usage of the microphone in mono

mode, and part (b) shows the stereo mode.

Figure 7. Typical microphone application

Concerning the stereo configuration, the LR pins of the involved digital microphones must

be respectively set to Vdd and gnd. This setting will produce the output signals depicted in

Figure 8 below. The succession of data valid and Hi-Z allows shortening the digital outputs

between each other to share the same data line.

Figure 8. Output data timing in stereo configuration

Concerning the schematic, the project must follow the recommended connections of

Figure 7 according to the desired configuration. Additionally, two capacitors (C1 and C2)

can be considered to ensure suitable supply decoupling. Generally, ST recommends two

different values, C2 = 10 µF working at low frequency and C1 = 100 nF working in the higher

frequency domain. These capacitors are the recommended values when the application