
PN6280_Hardware Design
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USB bus is mainly used for data transmission, software upgrade, module program testing. Working in
the USB mode of the high-speed line, if you need ESD design, ESD protection devices must meet the
junction capacitance value of less than 3pF, otherwise the larger junction capacitance will cause
waveform distortion, and affect the bus communication. The differential impedance of differential data
lines should be controlled at 90ohm
±10%, and lines should be protected up and down, and can’t be
crossed with other lines. USB connection circuit is as follows.
Figure 3-6 USB Circuit
Note: If you use the serial port communication, the DM/DP reserved test points
respectively in order to download software. If DM/DP is used to communicate with the
MCU, the position of the DM / DP signal near the module needs to reserve a test point and
the DM/DP requires a series 0R resistor. The resistor is placed near the module and the
test point is placed between module and resistor.