N58 Hardware User Guide
Chapter 5 Application Interfaces
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5.4 Audio Interfaces
The N58 module provides analog audio input and output interfaces (MIC and SPK).
5.4.1 Analog Audio Input Interfaces
Pin Name
Pin No.
I/O
Function
Remarks
MIC_P
18
AI
MIC input positive
Internal built-in bias voltage.
MIC_N
19
AI
MIC input negative
N58 supports one differential MIC input, with internal built-in bias voltage. The following figure shows
the reference design of differential MIC input.
Figure 5-28 Reference design of differential MIC input
B 1
B 2
DNI
DNI
DNI
MIC_ P
MIC_ N
C 2
C 3
C 4
D 1
D 2
MIC
Schematic design guidelines:
D1 and D2 are TVS diodes to prevent ESD introduced at MIC from damaging the module.
C2, C3, and C4 are mainly used to filter out interference signals. Adjust parameters based on the
actual debugging conditions.
B1 and B2 are ferrite beads used to filter out high-frequency noise. It is recommended that the
ferrite beads should have an impedance of 1800 Ω or higher at 100 MHz and a DC resistance
lower than 1.5 Ω. It is recommended to use ferrite beads specifically for audio.
It is recommended to use an electret microphone that embeds RF filter dual capacitors (such as
10 pF and 33 pF) to filter out RF interference from interference sources, helping reduce TDD
coupling noise.
