LTE Module Series
EM05 Hardware Design
EM05_Hardware_Design Confidential / Released 32 / 59
3.9. USB Interface
The following table shows the pin definition of USB interface.
Table 10: Pin Definition of USB Interface
EM05 is compliant with USB 2.0 specification. It can only be used as a slave device. Meanwhile, it
supports high speed (480Mbps) and full speed (12Mbps) mode. The USB interface is used for AT
command communication, data transmission, GNSS NMEA output, software debugging and firmware
upgrade. The following figure shows the reference circuit of USB interface.
USB_DP
USB_DM
GND
USB_DP
USB_DM
GND
R1
R2
Close to Module
R3
R4
Test Points
ESD Array
NM_0R
NM_0R
0R
0R
Minimize these stubs
Module
MCU
Figure 19: Reference Circuit of USB Interface
In order to ensure the integrity of USB data line signal, R1, R2, R3 and R4 components must be placed
close to the module, and also these resistors should be placed close to each other. The extra stubs of
trace must be as short as possible.
In order to ensure the USB interface design corresponding with the USB 2.0 specification, please comply
with the following principles:
It is important to route the USB signal traces as differential pairs with total grounding. The impedance
of USB differential trace is 90Ω.
USB differential data bus (+)
Require differential impedance of 90Ω
USB differential data bus (-)
Require differential impedance of 90Ω
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