Usb Interface - Quectel EC21 Series Hardware Design

3.10. USB Interface

EC21 series contains one integrated Universal Serial Bus (USB) interface which complies with the USB
2.0 specification and supports high-speed (480 Mbps) and full-speed (12 Mbps) modes. The USB
interface can only serve as a slave device.
EC21 series module can be used for AT command communication, data transmission, GNSS NMEA
sentences output, software debugging, firmware upgrade and voice over USB.
The following table shows the pin definition of USB interface.
Table 11: Pin Description of USB Interface
Pin Name Pin No.
USB_DP 69
USB_DM 70
USB_VBUS 71
GND 72
For more details about the USB 2.0 specifications, visit http://www.usb.org/home.
The USB interface is recommended to be reserved for firmware upgrade in customers' designs. The
following figure shows a reference circuit of USB interface.
EC21_Series_Hardware_Design
I/O Description
AIO USB differential data (+)
AIO USB differential data (-)
DI USB connection detect
- Ground
Figure 19: Reference Circuit of USB Application
LTE Standard Module Series
Comment
USB 2.0 Compliant.
Require differential impedance of 90 Ω.
If unused, keep them open.
Typical 5.0 V
-
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