TOBY-L2 and MPCI-L2 series - System Integration Manual
UBX-13004618 - R07
Advance Information
Design-in
Page 105 of 158
2.6
Data communication interfaces
2.6.1
Universal Serial Bus (USB)
2.6.1.1
Guidelines for USB circuit design
The
USB_D+
and
USB_D-
lines carry the USB serial data and signaling. The lines are used in single ended mode
for full speed signaling handshake, as well as in differential mode for high speed signaling and data transfer.
USB pull-up or pull-down resistors and external series resistors on
USB_D+
and
USB_D-
lines as required by the
USB 2.0 specification
are part of the module USB pin driver and do not need to be externally provided.
The additional
VUSB_DET
input is available as optional feature to sense the host VBUS voltage (5.0 V typical).
The
VUSB_DET
functionality is not supported by TOBY-L2 “00”, “01”, and “50” product versions: the
pin should be left unconnected or it should not be driven high (for more details, see section 1.9.1.1).
The
VUSB_DET
pin is not available on MPCI-L2 series modules.
Routing the USB pins to a connector, they will be externally accessible on the application device. According to
EMC/ESD requirements of the application, an additional ESD protection device with very low capacitance should
be provided close to accessible point on the line connected to this pin, as described in Figure 53 and Table 33.
The USB interface pins ESD sensitivity rating is 1 kV (Human Body Model according to JESD22-A114F).
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 accessible points.
The
USB_D+
and
USB_D-
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 DEVICE
CONNECTOR
VBUS
D+
D-
GND
28
USB_D+
27
USB_D-
GND
USB HOST
PROCESSOR
D+
D-
GND
38
USB_D+
36
USB_D-
GND
USB DEVICE
CONNECTOR
VBUS
TOBY-L2 series
TOBY-L2 series
MPCI-L2 series
MPCI-L2 series
D+
D-
GND
38
USB_D+
36
USB_D-
GND
USB HOST
PROCESSOR
VBUS
4
VUSB_DET
4
VUSB_DET
D1
D2
D1
D2
VBUS
Figure 53: USB Interface application circuits
Reference
Description
Part Number - Manufacturer
D1, D2
Very Low Capacitance ESD Protection
PESD0402-140 - Tyco Electronics
Table 33: Component for USB application circuits