Smart Module Series
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4.18.4. Reference Circuit Design for Loudspeaker Interface
EN
GPIO_100
C2
D1
D2
NC
+IN
-IN
VO2
GND
VDD
VO1
F2
F1
C1
R2
R3
R1
C3
C4
C5
C7
C6
Audio PA
LINE_OUT_P
LINE_OUT_M
VPH_PWR
10
μ
F
10
μ
F
82 K
82 K
10 K
22
μ
F
1
μ
F
33 pF 33 pF
100 pF
Figure 28: Reference Circuit Design for Loudspeaker Interface
4.18.5. Audio Interfaces Design Considerations
To decrease radio or other signal interference, RF antennas should be placed away from audio
interfaces and audio traces. Additionally, keep power traces far away from the audio traces and do not
route them in parallel.
The differential audio traces must be routed according to the differential signal layout rule.
4.19. Emergency Download Interface
USB_BOOT is an emergency download interface. Pull up to LDO9_1V8 during power-up will force the
module to enter emergency download mode. There is an emergency option when start-up failures or
operational abnormalities occur. For firmware upgrade and debugging in the future, please reverse the
following reference circuit design.
LDO9_1V8
S1
Module
USB_BOOT
R1
10K
Figure 29: Reference Circuit Design for Emergency Download Interface
