Novatel OEM6, User Manual

Page: 133 / 175

OEM6 Family Installation and Operation User Manual Rev 7 133
Figure 65: OEM628 CAN Transceiver Implementation Schematic
Only use a 120 Ω termination resistor when the CAN device is used at one end of the CAN bus. Multiple
terminations along the length of the CAN bus will degrade performance for all CAN devices on that bus.
The slew rate adjustment resistor (R101) value in Figure 65 on page 133 sets the slew rate for
applications for SAE J1939 agricultural applications. Other applications may require a different slew rate.
Refer to the transceiver data sheet for more information.
Table 26: CAN Critical Components
C.1.4 USB Interface
The OEM628 includes one USB 2.0 full speed (12 Mbps) / low speed (1.5 Mbps) interface.
For signal integrity and EMI reasons, route differential data traces as a 90 Ω differential pair. A small
value common mode choke (as shown in the figure below) may improve the radiated emissions
performance. Small ferrite beads are shown on VBUS and UID lines as a contingency against radiated
emissions.
As long as the 90 Ω impedance is maintained while routing the USB D+/D- signals, no matching resistors
are required. The pull resistors for mode selection are part of the USB PHY on the receiver card (no
external pull resistors are required on the data lines to set host or device modes).
There is an ESD protection device on the receiver card for the USB differential pair. An additional device
may be added near the USB connector but care should be taken not to cause a mismatch on the
differential pair—stubs or large capacitance ESD protection should be avoided.
The OEM628_VBUS trace should be capable of handling at least 100 mA. The traces for VBUS and UID
should be routed away from any high current switching nets and high frequency signals. The common
mode choke, ferrite beads and bypass capacitor should be placed as close as possible to the USB
connector.
When the USB interface is used as a device, the UID (pin 14) may be omitted (left as a no connect) and
a standard USB Type-B connector used.
CAN1+
CAN1-
OEM628_CAN1RX
P1502, pin 10
OEM628_CAN1TX
P1502, pin 11
U100
TI SN65HVD231
3V3
R100
5.1K-1%
C100
0.1µF
R101
22.1K-1%
C102
22pF
R102
120
C101
22pF
120 ohm termination only
required if unit is on the
end of the CAN bus
(not all CAN devices
require termination)
FB100
FB101
U101
PLC03-6
IO1
GND1
GND2
IO2 IO4
GND4
GND3
IO3
1
2
3
4
8
7
6
5
D
D
D D
D
D
D
1
4
8
2
3
5
7
6
D
R
RS
GND
VCC
VREF
CANH
CANL
Designator Manufacturer Manufacturer Part Number
FB100, FB101 TDK MMZ1005B800C
U100 Texas Instruments SN74LVC1G86DCK
U101 Semtech
Bourns
OnSemi
LC03-6.TBT
CDNBS08-PLC03-6
LC03-6R2G
C101, C102 various (22 pF 5% 50V COG 0603)