TOBY-L4 series - System Integration Manual
UBX-16024839 - R04
Design-in
Page 86 of 143
2.6
Data communication interfaces
2.6.1
USB interface
2.6.1.1
Guidelines for USB circuit design
Different application circuits can be implemented for the USB interface according to specific use-case:
USB 2.0 interface, with the module acting as USB device, as illustrated in Figure 41 and Table 32
USB 2.0 interface, with the module acting as USB host, as illustrated in Figure 42 and Table 33
USB 3.0 interface, with the module acting as USB device, as illustrated in Figure 43 and Table 34
USB pull-up or pull-down resistors and external series resistors on the
USB_D+
and
USB_D–
lines as required by
the
USB 2.0 specification
are part of the module USB pins driver and do not need to be externally provided.
Series DC decoupling capacitors are internally provided on the
U
and
USB_SSTX–
lines as required by
the
USB 3.0 specification
[4] and do not need to be externally provided.
The
U
/
USB_SSTX–
USB Super-Speed differential transmitter data output lines of the module must be
connected to the USB Super-Speed differential receiver data input lines of the external USB 3.0 host.
The
U
/
USB_SSRX–
USB Super-Speed differential receiver data input lines of the module must be
connected to the USB Super-Speed differential transmitter data output lines of the external USB 3.0 host, with
series DC decoupling capacitors being provided on the host side as per the
USB 3.0 specification
Routing the USB pins to a connector, they will be externally accessible on the application device. According to
the EMC/ESD requirements of the application, an additional ESD protection device with very low capacitance
should be provided close to the accessible point on the line connected to this pin.
The USB interface pins ESD sensitivity rating is 1 kV (Human Body Model according to JESD22-A114F).
A higher protection level could be required if the lines are externally accessible and it can be achieved by
mounting a very low capacitance (i.e. less or equal to 1 pF) ESD protection (e.g. Tyco Electronics
PESD0402-140 ESD protection device) on the lines connected to these pins, close to the accessible points.
The USB pins of the modules can be directly connected to the USB host application processor without additional
ESD protections if they are not externally accessible or according to EMC/ESD requirements.
D+
D–
GND
28
USB_D+
27
USB_D–
GND
USB 2.0 DEVICE
CONNECTOR
VBUS
D+
D–
GND
USB 2.0 HOST
PROCESSOR
TOBY-L4 series
VBUS
4
VUSB_DET
D1
D2
D3
C1
C1
28
USB_D+
27
USB_D–
GND
TOBY-L4 series
4
VUSB_DET
168
USB_ID
168
USB_ID
170
U
171
USB_SSRX–
175
U
176
USB_SSTX–
170
U
171
USB_SSRX–
175
U
176
USB_SSTX–
Figure 41: USB 2.0 interface application circuits, with TOBY-L4 series module acting as a USB device
Reference
Description
Part Number - Manufacturer
C1
100 nF Capacitor Ceramic X7R 0402 10% 16 V
GRM155R61A104KA01 - Murata
D1, D2, D3
Very Low Capacitance ESD Protection
PESD0402-140 - Tyco Electronics
Table 32: Component for USB 2.0 interface application circuits, with TOBY-L4 series module acting as a USB device