Doc Title Wireless smart audio module
Number
WMB20150921
Document No.: WMB20150921 Page 14 of 21
Figure 2-5 USB host interface
Please follows the following design rule to populate the USB host interface:
Item Parameter
Signal Group USB
Topology Differential Pair Point-to-Point
Reference Plane Ground Referenced
Characteristic Trace Impedance (Zo) 90 Ω ±10%
Trace Width 4 mils
Serpentine Spacing(center to center) 8.5 mils
Minimum Isolation Spacing to Clock Signals 50 mils
Minimum Isolation Spacing to Low-Speed Signals 20 mils
Minimum Isolation Spacing to other USB Pair 20 mils
Total Length (with package length) Max = 8000 mils
Maximum Recommended Via Count 2 (per side)
DM to DP Length Matching(with package length) Match total length to within ±10 mils
Table 2-6 LinkPlay WiFi Audio A31 USB design rule
2.7. Power supply
A31 module can be powered with single power supply with voltage between 3.5V and 5.5V. The peak current is
around 300mA, the normal working current is 170mA. In sleep mode (when Wi-Fi is off), the current is 20mA.
The power supply is important for system stability and Wi-Fi performance. It is recommended to use 100uF and
10uF decoupling capacitor in parallel to reduce the ripple of power supply.
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