Reference Circuit Design For Loudspeaker Interface; Audio Interfaces Design Considerations; Emergency Download Interface - Quectel SC690A Series Hardware Design

4.18.4. Reference Circuit Design for Loudspeaker Interface

GPIO_100
C1
LINE_OUT_P
C2
LINE_OUT_M
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.
Figure 29: Reference Circuit Design for Emergency Download Interface
SC690A_Series_Hardware_Design
Audio PA
EN
R1
NC
10 K
10 μF R2 82 K
+IN
R3
10 μ F
82 K
-IN
USB_BOOT
Module
VPH_PWR
VO2
C6
GND
100 pF
VDD
VO1
C4
C3
22 μ F
1 μ F
LDO9_1V8
S1
R1
10K
Smart Module Series
F1
F2
D1 D2
C5 C7
33 pF 33 pF
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