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N720 OpenLinux
Hardware User Guide
Copyright © Neoway Technology Co., Ltd
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commissioning. The module can be used as USB Device. It is an option for customers. The
recommended USB circuit is shown in Figure 3-13.
Figure 3-13 USB connection
ESD1
C2
ESD2
ESD3
Power
Switch
MCU_EN
USB_ID
USB_DP
USB_DM
USB_VBUS
N720 module
USB_VBUS
USB_DM
USB_DP
USB_ID
GND
USB Connector
C1
1uF
22pF
Figure 3-14 Reference design of USB OTG function
ESD1
C1
C2
ESD2
ESD3
1uF
22pF
USB_VBUS
USB_DM
USB_DP
USB_ID
USB Device
USB_ID
USB_DP
USB_DM
USB_VBUS
N720 module
ESD4
C4
C5
5V
DC-DC
VCC
IN
EN
OTG_5V_EN
OUT
Schematic Design Recommendations
Connect a 1μF and a 22pF filter capacitors in parallel to the USB_VBUS pin. An ESD component
is required for the USB_VBUS line.
The junction capacitance of the ESD protection diodes for USB_DP and USB_DM should be
lower than 1pF if possible.
To enter sleep mode, shut down USB_VBUS. Add a switch to USB_VBUS to control it by MCU.
See Figure 3-14. For the switch circuit, see Figure 3-3.
USB_ID is used for the OTG function. Pull USB_ID to low level, and the module will work in host
mode. To use the OTG function, supply a voltage to USB_VBUS. See Figure 3-14.