N27 Hardware User Guide
Chapter 4 Application Interfaces
Copyright © Neoway Technology Co., Ltd. All rights reserved.
27
Figure 4-6 shows the recommended USB connection.
Figure 4-6 USB connection
ESD1
USB_DP
_
N27 module
GND
USB Connector
R1
C2
DNI
1uF
ESD2
ESD3
USB_DM
USB_VBUS
USB_DP
USB_ID
USB_VBUS
USB DM
USB_ID
GND
TP1
TP2
TP3
Schematic guidelines
Parallel a 1
μF filter capacitor 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.
Connect common-mode inductors to USB_DP and USB_DM in series to prevent the EMI
jamming generated by USB.
PCB layout guidelines:
Place filer capacitors on the USB_VBUS line as close to the pin of the module as possible and
the ESD triode as close to the USB connector as possible.
Place the ESD triodes on USB_DP and USB_DM lines as close to the USB connector as
possible.
USB data lines adopt differential trace design, in which the differential impedance is limited to
90Ω. Isolate the traces from other signal traces by surrounding them with ground.
Keep the trace of USB_VBUS wider than 0.3 mm.
4.3.2 UART
Signal
Pin
I/O
Function
Remarks
UART0_TXD
1
48
DO
Data TX
Software (open) version: used as
UART1_TXD.
UART0_RXD
1
49
DI
Data RX
Software (open) version: used as
