Confidential
MANUAL
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3.1.6 Analog Audio Signals Recommended Circuitry
3.1.6.1 ATMS path
An application using the analog audio interface must re-reference the signal from its own internal BIAS to AGND
received from the module.
The figure below shows an example of a microphone implementation.
Microphone solution:
The microphone should preferably be connected to its pre-amplifier differentially, which will minimize noise picked
up along the way from the microphone to its amplifier. If the impedance is the same on both microphone lines, and
the lines are run in parallel, the same amount of noise is picked up on both lines. This noise is then removed in the
differential amplifier stage.
Figure 23: ATMS Microphone Recommendation
Differential Line-level solution:
The differential codec signal is input between L+ and L-. Using the same power supply for the differential amplifier
as for the codec assures that the DC-level (BIAS) is half of the supply voltage.
Figure 24: ATMS Differential Recommendation
