TCAN1042-Q1 Datasheet, PDF (21/32 Pages) Texas Instruments – Automotive Fault Protected CAN Tranceiver

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10 Application and Implementation
TCAN1042-Q1, TCAN1042V-Q1, TCAN1042H-Q1
TCAN1042HV-Q1, TCAN1042G-Q1, TCAN1042GV-Q1
TCAN1042HG-Q1, TCAN1042HGV-Q1
SLLSES9 – FEBRUARY 2016
NOTE
Information in the following applications sections is not part of the TI component
specification, and TI does not warrant its accuracy or completeness. TI’s customers are
responsible for determining suitability of components for their purposes. Customers should
validate and test their design implementation to confirm system functionality.
10.1 Application Information
These CAN transceivers are typically used in applications with a host microprocessor or FPGA that includes the
data link layer portion of the CAN protocol. Below are typical application configurations for both 5 V and 3.3 V
microprocessor applications. The bus termination is shown for illustrative purposes.
10.2 Typical Applicationspurposes. Typical
Node 1
MCU or DSP
CAN
Controller
CAN
Transceiver
Node 2
MCU or DSP
CAN
Controller
CAN
Transceiver
Node 3
MCU or DSP
CAN
Controller
CAN
Transceiver
Node n
(with termination)
MCU or DSP
CAN
Controller
CAN
Transceiver
R_TERM
R_TERM
Figure 16. Typical 5 V Application
10.2.1 Design Requirements
10.2.1.1 Bus Loading, Length and Number of Nodes
The ISO11898 Standard specifies a maximum bus length of 40m and maximum stub length of 0.3m. However,
with careful design, users can have longer cables, longer stub lengths, and many more nodes to a bus. A large
number of nodes requires transceivers with high input impedance such as the TCAN1042 family of transceivers.
Many CAN organizations and standards have scaled the use of CAN for applications outside the original
ISO11898. They have made system level trade offs for data rate, cable length, and parasitic loading of the bus.
Examples of some of these specifications are ARINC825, CANopen, DeviceNet and NMEA2000.
A CAN network design is a series of tradeoffs, but these devices operate over wide common-mode range. In
ISO11898-2 the driver differential output is specified with a 60 Ω load (the two 120 Ω termination resistors in
parallel) and the differential output must be greater than 1.5 V. The TCAN1042 family is specified to meet the 1.5
V requirement with a 50Ω load incorporating the worst case including parallel transceivers. The differential input
resistance of the TCAN1042 family is a minimum of 30 kΩ. If 100 TCAN1042 family transceivers are in parallel
on a bus, this is equivalent to a 300Ω differential load worst case. That transceiver load of 300 Ω in parallel with
the 60Ω gives an equivalent loading of 50 Ω. Therefore, the TCAN1042 family theoretically supports up to 100
transceivers on a single bus segment with margin to the 1.2 V minimum differential input at each node. However
for CAN network design, margin must be given for signal loss across the system and cabling, parasitic loadings,
network imbalances, ground offsets and signal integrity thus a practical maximum number of nodes is typically
much lower. Bus length may also be extended beyond the original ISO11898 standard of 40m by careful system
design and datarate tradeoffs. For example CANopen network design guidelines allow the network to be up to
1km with changes in the termination resistance, cabling, less than 64 nodes and significantly lowered data rate.
This flexibility in CAN network design is one of the key strengths of the various extensions and additional
standards that have been built on the original ISO11898 CAN standard. In using this flexibility comes the
responsibility of good network design and balancing these tradeoffs.
Copyright © 2016, Texas Instruments Incorporated
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Product Folder Links: TCAN1042-Q1 TCAN1042V-Q1 TCAN1042H-Q1 TCAN1042HV-Q1 TCAN1042G-Q1
TCAN1042GV-Q1 TCAN1042HG-Q1 TCAN1042HGV-Q1