LTE Standard Module Series
EG915U-EU_Hardware_Design 41 / 81
Pin definition of the USB interface is here as follows:
Table 13: Pin Definition of USB Interface
For more details about the USB 2.0 specifications, please visit http://www.usb.org/home.
It is recommended to reserve test points for debugging and firmware upgrade in customers’ designs. The
following figure shows a reference circuit of USB interface.
It is recommended to reserve test points for debugging
and firmware upgrading in customers’ designs.
USB_DP
USB_DM
GND
USB_DP
USB_DM
GND
L1
Close to Module
R3
R4
Test Points
ESD Array
NM_0R
NM_0R
Minimize these stubs
Module
MCU
USB_VBUS
USB_VBUS
Figure 18:
Reference Circuit of USB Application
A common mode choke L1 is recommended to be added in series between the module and customer
’s
MCU in order to suppress EMI spurious transmission. Meanwhile, the 0
Ω resistors (R3 and R4) should
be added in series between the module and the test points so as to facilitate debugging, and the resistors
are not mounted by default. In order to ensure the integrity of USB data line signal, L1, R3 and R4
components must be placed close to the module, and also resistors R3 and R4 should be placed close to
each other. The extra stubs of trace must be as short as possible.
Voice over USB
N
Pin Name
Pin No.
I/O
Description
Comment
USB_VBUS
8
AI
USB connection detect
Typical 5.0 V
Minimum 3.5 V
USB_DP
9
AIO
USB differential data (+)
USB 2.0 compliant.
Require differential
impedance of 90 Ω.
If unused, keep it open.
USB_DM
10
AIO
USB differential data (-)