Users Manual
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The common mode inductor should be close to the USB connector side.
It is required to control the 90 ohm differential impedance with an error of ±10%.
The differential line length error is controlled within 6mm.
If the USB has a charging function, please note that the VBUS cable is as wide as possible.
If there is a test point, try to avoid the split line and put the test point on the path of the trace.
Table 5.1:
Pin Signal Length(mm) Length Error
P-N
14 USB_DP 26.2
0.2mm
13 USB_DM 26.5
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The module supports 3 analog audio signals. Analog signals are susceptible to interference from high speed digital
signals. So stay away from high-speed digital signal lines. The module supports the WCDMA/LTE system, and the
WCDMA/LTE signal can interfere with the audio by coupling and conduction.
The users should pay attention to keeping the audio trace away from the WCDMA/LTE antenna and VBAT during
PCB layout and routing. The filter capacitor of the audio is preferably placed close to the module end and placed
next to the interface end. The audio output should be routed according to the differential signal rules.
The conducted interference is mainly caused by the voltage drop of VBAT. If the Audio PA is directly powered by
VBAT, it is easier to hear the fzizig sound at the SPK output. Therefore, it is better to connect in parallel with the
input of the Audio PA in the schematic design. Some large capacitance capacitors and series magnetic beads.
FDD and GND also have a great relationship. If GND is not handled well, many high-frequency interference
signals will interfere with MIC and Speaker through devices such as bypass capacitors, so users should
ensure good performance of GND during PCB design.
The serial port interface of the module should also be kept as short as possible. It is best to walk in a
group when routing, and do not distract the wires.
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