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L816-AM Hardware User Manual
Page 26 of 42
3.4
USB Interface
The L816-AM module supports USB 2.0 which is compatible with USB High-Speed (480 Mbit/s) and USB
Full-Speed (12 Mbit/s). For the USB timing and electrical specification of L816-AM module, please refer to
“
Universal Serial Bus Specification 2.0
”
.
3.4.1 USB Interface Definition
Pin
Pin Name
I/O
Reset Value
Pin Description
Type
15
VBUS
PI
USB power supply
2.0---5.25V
14
USB_DN
IO
T
USB Data Negative
0.3---3V
13
USB_DP
IO
T
USB Data Positive
0.3---3V
The VBUS power supply is used as the detection of the USB port; after VBUS is powered on, the USB
function of the module will be enabled and the enumeration will begin. The VBUS pin is only used for the
detection of USB port, and the supply current is about 1mA. When USB_DN & USB_DP are disconnected,
the module will not enter sleep mode for the case if VBUS power is supplied.
The USB driver will map 3 COM ports and 4 NCM ports, which are described as follows:
2 COM ports are used to send AT Commands.
1 COM port is used to capture LOG information with debugging softwares.
4 NCM ports are virtual network ports, which are used to initiate the data service.
Note:
One COM port can be used as the Modem COM port to initiate the data service. Since the speed
of the Modem COM port is not sufficient for the 150 Mbps peak downlink speed requirement for
LTE, so it is not recommended to be used.
3.4.2 USB Interface Application
The reference circuit is shown in Figure 3-10:
Figure 3-10 Reference Circuit for USB Interface
