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Technical White Paper

How automotive-qualified electromagnetic-compliant 3.3V
CAN FD transceivers improve ECU performance

Vikas Kumar Thawani, Deep Banerjee, Lokesh Kumar Gupta, Sachin Jadhav, Vinay Agarwal
ABSTRACT
Modern-day automotive systems provide a plethora of functions to help improve vehicle safety, performanceand comfort. Design engineers create powertrains for advanced driver assistance systems, body electronics
and lighting, infotainment and safety systems that include a large number of electronic control units (ECUs) toperform various electromechanical functions. ECUs exchange control and data-log information through in-vehicle
network buses. Among network protocols such as Controller Area Network (CAN), Local Interconnect Network(LIN), FlexRay and Ethernet, the CAN bus remains the most popular choice given its ease of use, goodcommon-mode noise rejection, priority-based messaging, bitwise arbitration to handle bus contention, and error
detection and recovery features.
Until now, a majority of CAN transceivers deployed in vehicles have been based on a 5V driver andreceiver supply. This is because the CAN physical layer (International Organization for Standardization[ISO] 11898-2:2024) and CAN component-level electromagnetic compliance (EMC) standard (International
Electrotechnical Commission [IEC] 62228-3) provide specifications and pass/fail limits only for 5V-supplied CAN
transceivers. There are subsystems that need a 5V power rail only for the CAN transceiver. A 3.3V-supplied
CAN transceiver can simplify the power-stage designs of ECUs by eliminating the required 5V rail, while being
fully interoperable with 5V CAN transceivers on the same network bus and meeting strict automotive EMC
requirements. This white paper introduces TI’s TCAN3403-Q1 and TCAN3404-Q1 automotive-qualified and
EMC-certified 3.3V CAN Flexible Data Rate (FD) transceivers.

Table of Contents
1 Introduction.............................................................................................................................................................................2
2 5V CAN Transceiver................................................................................................................................................................4
3 TI's TCAN3403-Q1, TCAN3404-Q1 CAN FD Transceivers................................................................................................... 5
4 Interoperability (IOPT) of TCAN340x-Q1...............................................................................................................................6
5 EMC of TCAN340x-Q1 ............................................................................................................................................................8
6 Benefits of TCAN340x-Q1 over competition 3.3V CAN offerings ......................................................................................8
7 Conclusion.............................................................................................................................................................................. 88 Revision History......................................................................................................................................................................8

List of Figures
Figure 1-1. Typical CAN Network................................................................................................................................................ 2
Figure 1-2. Application Schematic of a 5V CAN Transceiver...................................................................................................... 2
Figure 1-3. CAN Signaling, Diver and Receiver Representation................................................................................................. 3
Figure 2-1. CAN Transceiver Block Diagram...............................................................................................................................4
Figure 3-1. Application Schematic of a 3.3V CAN Transceiver................................................................................................... 5
Figure 3-2. Waveform Comparison of a 5V CAN and 3.3V CAN Transceiver............................................................................. 6
Figure 4-1. 5V Homogeneous Network CAN FD Frame Waveform............................................................................................ 7
Figure 4-2. 3.3V and 5V Heterogeneous Network CAN FD Frame Waveform............................................................................7

List of Tables
Table 2-1. 5V CAN Transceiver Specifications............................................................................................................................ 4
Table 3-1. TCAN340x-Q1 Family of Devices............................................................................................................................... 5
Table 3-2. 3.3V CAN Transceiver Specifications......................................................................................................................... 5

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Trademarks

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Table 6-1. Feature Comparison of TCAN340x-Q1 Against Competition 3.3V CAN Devices.......................................................8

Trademarks
All trademarks are the property of their respective owners.

1 Introduction
With the electrification of vehicles happening at a rapid pace, multiple ECUs are deployed all through the vehicle.
These subsystems talk to each other through a CAN network.
Figure 1-1 shows a CAN network.
Node 1

Node 2

Node 3

Node n(with termination)

MCU or DSP

MCU or DSP

MCU or DSP

MCU or DSP

CANController

CAN
Controller

CAN
Controller

CAN
Controller

CAN
Transceiver

CAN
Transceiver

CAN
Transceiver

CAN
Transceiver
RTERM

RTERM

Figure 1-1. Typical CAN Network
Each CAN node consists of at least three components: a CAN transceiver, a microcontroller (MCU) or
microprocessor (MPU), with an embedded CAN protocol controller and a power device (a DC/DC converteror linear regulator) that converts the automotive battery voltage to 5V. Additionally, in case the MCU or MPU’s
input/output (I/O) voltage is 3.3V, a separate 3.3V power device is used on the ECU’s printed circuit board(PCB). Figure 1-2 shows a simplified schematic.
VBAT

VOUT

VIN

5-V Voltage
Regulator

3
VCC

VDD
Port x

8

CANH
STB

MCU
VIN

RXD
CAN FD
Controller
TXD

3.3-V Voltage
Regulator

7

5-V CAN
4
RXD
1
TXD

VIO

GND

CANL

6

5

VOUT

Optional:
Terminating Node

Figure 1-2. Application Schematic of a 5V CAN Transceiver2

How automotive-qualified electromagnetic-compliant 3.3V CAN FD
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Introduction

Typical CAN bus signals consist of dominant and recessive phases. A CAN driver produces a differential signalof at least 1.5V across a 60Ω load during the dominant phase, whereas the driver weakly biases the bus to acommon-mode 2.5V level during the recessive phase. This signaling is designed for bitwise arbitration, and thedevice with the highest priority ID (the CAN frame identification field with the most dominant bits) takes controlof the bus, since the dominant (strong) drive is able to overcome recessive (weak) biasing. The receiving nodesmonitor CAN high and CAN low differential signals and can decode the CAN message as long as the signal is
above 900mV (the dominant threshold) or below 500mV (the recessive threshold).

Figure 1-3. CAN Signaling, Diver and Receiver Representation
VD = VCANH – VCANLFor driver: VOD(DOM) ≥ 1.5V @ 60 Ω load
For receiver: VID(DOM) ≥ 900mV, VID(rec) ≤ 500mVA CAN wiring harness is spread throughout the vehicle. Any common-mode disturbance generated by the
CAN transceiver can result in emissions that can impact the functionality of other automotive subsystems.
Similarly, the harness is susceptible to electromagnetic interference from other modules. Thus, electromagnetic
compliance is an important requirement for any automotive CAN transceiver. Different subsystems can have
CAN transceivers from different semiconductor vendors; thus, interoperability is another requirement for any
CAN transceiver to be used in a mainstream vehicle network.

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2 5V CAN Transceiver
As shown in Figure 2-1, for the driver to produce a minimum differential voltage of 1.5V across the CAN high and
CAN low terminals, high- and low-side transistors (highlighted in the dotted-red rectangle in Figure 2-1) must be
sized appropriately so that the maximum drop across them is 3V when operating from a 4.5V supply (since themain 5V supply can vary by ±10%).
VIO

VCC
5

3

VIO

7
TSD

TXD

1

CANH

Dominant
time-out
6

CANL

VIO

STB

8

Mode Select

UVP

VIO

RXD

4

Logic Output

MUX
WUP Monitor
Low Power Receiver
2
GND

Figure 2-1. CAN Transceiver Block Diagram
The CAN bus transceiver may be the only 5V component in the subsystem. With the modern MCU’s I/O supply
going down to 3.3V, it is possible to eliminate the 5V rail altogether, resulting in power-stage simplification andcost savings by reducing the bill of materials and PCB space. A high bus-fault-tolerant CAN bus transceiver thatis footprint-compatible to standard 5V CAN transceivers, and that operates from a single 3.3V supply, can help
simplify designs and reduce cost by eliminating the need for a dedicated 5V supply.
Table 2-1. 5V CAN Transceiver Specifications
Parameter

Conditions

Min (V)

VCANH

Dominant output, Bus load 50 Ω
≤ RL ≤ 65 Ω

2.75

4.5

0.5

2.25

VCANL

4

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TI's TCAN3403-Q1, TCAN3404-Q1 CAN FD Transceivers

3 TI's TCAN3403-Q1, TCAN3404-Q1 CAN FD Transceivers
TI has released two automotive-qualified and EMC-certified 3.3V CAN FD transceivers. Table 3-1 shows thedifferences between the TCAN3403-Q1 and TCAN3404-Q1.
Table 3-1. TCAN340x-Q1 Family of Devices
Part Number

Pin 5

Pin 8

TCAN3403-Q1

Ultra-low power shutdown mode

TCAN3404-Q1

Low voltage I/O support

Low power standby mode with remote
wakeupA few more things to note:•••

Even with 3V minimum supply (since 3.3V main supply can vary by ±10%), the devices are designed fora minimum 1.5V of differential output voltage with a 50Ω bus load. This maintains compliance to the VOD
specification in ISO 11898-2(2024).
Receiver thresholds are exactly same as standard 5V CAN transceivers and maintains compliance toISO11898-2 (2024).
Single-ended specifications are listed in Table 3-2, which is a slight deviation from CAN physical layer
standard ISO 11898-2(2024).
Table 3-2. 3.3V CAN Transceiver Specifications

Parameter

Conditions

Min (V)Max (V)

VCANH

Dominant output, Bus load 50 Ω
≤ RL ≤ 65 Ω

2.25

VCC

VCANL
VCANH, VCANL

0.5

1.25

Recessive

1.9 V (typical)

Driver transistors (highlighted in dotted red rectangle in Figure 2-1) have to be sized so that the drop acrossthe high and low sides is a combined 1.5V maximum at a 3V operating bus supply. This reduction in theminimum operating supply mandates device recessive biasing to be positioned at 1.9V, as opposed to 2.5V for
standard 5V CAN transceivers. Because CAN is a differential interface, single-ended voltages in the dominant
and recessive states are not crucial for proper operation or communication. This means that the devices arecompatible with ISO 11898-2 (2024).
Figure 3-1 is an application diagram with TCAN3404-Q1 demonstrating single 3.3V supply regulator to run the
MCU and the CAN transceiver, thereby eliminating the 5V regulator that standard 5V CAN transceivers need.
VIN

VIN

VOUT

3.3 V Voltage
Regulator

3
VCC
VDD
Port x

8
5

CANH

SHDN
TCAN3404MCURXDCAN FD
Controller
TXD

7

STB

4
RXD
1
TXD

GND

CANL

6

Optional:
Terminating Node

Optional: Filtering,Transient and ESD

Figure 3-1. Application Schematic of a 3.3V CAN Transceiver

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Figure 3-2 compares single device level waveforms between TCAN340x-Q1 and standard 5V CAN.

Figure 3-2. Waveform Comparison of a 5V CAN and 3.3V CAN Transceiver
When combining the TCAN3403-Q1 and TCAN3404-Q1 with 5V CAN transceivers on the same bus network,a slight recessive bias mismatch can have an impact on emissions. But proprietary design techniques
implemented in both devices maintain EMC compliance per IEC 62228-3 in both homogeneous (both nodes
in network, as in the TCAN340x-Q1) and heterogeneous (one node is the TCAN340x-Q1, the other node isstandard 5V CAN) network conditions.
Other features of the TCAN3403-Q1 and TCAN3404-Q1 are:••••A high bus-fault tolerance up to ±58V that maintains no device damage in the event of miswiring faults for
12V and 24V battery applications.
An extended common-mode operating voltage range of ±30V ensures the receiver continues to receive data
without disruption, even in the presence of a large ground potential difference or voltage interference.
Footprint compatibility to standard 5V CAN transceivers, while also having a shutdown feature that reduces
supply current consumption to <5µA, enabling seamless upgradability.
Package options offered in leaded small-outline integrated circuit (SOIC)-8, leadless very small-outline nolead (VSON)-8 with wettable flanks, and ultrasmall leaded small-outline transistor (SOT)-23.

Many 3.3V CAN transceivers were already available in the market, but none met both auto-qualification and
EMC certification requirements. The TCAN340x-Q1 is an option for automotive designers looking for a fullyinteroperable 3.3V CAN transceiver that overcomes EMC challenges in heterogeneous networks.

4 Interoperability (IOPT) of TCAN340x-Q1
As stated in the previous section, the TCAN340x-Q1 recessive biasing of CAN high and CAN low terminals
is 1.9V. This minor shift in common-mode voltage (compared to 2.5V for standard 5V CAN transceivers) falls
within the common-mode voltage range of −12V to +12V specified in ISO 11898-2 (2024). Also, this minor
shift in recessive bias level is inconsequential to the extended ±30V common-mode voltage range of theTCAN340x-Q1 when operating at 3.3V, allowing the TCAN340x-Q1 to communicate seamlessly with any otherISO 11898-2-compliant transceivers. The TCAN340x-Q1 is fully interoperable with other transceivers on thesame bus powered by a 5V supply.
TI’s TCAN340x-Q1 3.3V CAN transceiver family has been successfully tested by the internationally recognizedthird-party communications and systems group to the interoperability test specification for a high-speed CAN
transceiver. The TCAN340x-Q1 devices successfully passed homogeneous and heterogeneous network testing,and certificates are available upon request.

6

How automotive-qualified electromagnetic-compliant 3.3V CAN FD
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Interoperability (IOPT) of TCAN340x-Q1

In the C&S IOPT tests, TCAN340x-Q1 was tested in a 16-node linear homogenous network with all nodes at
2Mbps, and the device was tested in an 8-node homogeneous linear network at 5Mbps. Additionally, it waswith a 16-node 2Mbps network testing under heterogeneous condition (specifically four nodes being TCAN340xQ1 and 12 nodes being golden reference 5V CAN transceivers). Similarly, an 8-node 5Mbps network wastested in heterogeneous condition (two nodes being TCAN340x-Q1 and 6 nodes as golden reference 5V CAN
transceivers). Under all network conditions, failures such as CAN bus short to GND, CAN short to battery,ground shift between nodes and disconnection of nodes were intentionally introduced in the network on startup,
then failure was removed and communication integrity was checked. Additionally, TI performed internal testingfor various different networks (multi-node complex star topologies) with and without arbitration, and TCAN340xQ1 passed IOPT under all network conditions. Below are two waveforms during arbitration for homogeneous (all5V nodes) and heterogeneous (three TCAN340x-Q1 and 8 standard 5V CAN nodes) 11-node complex triple star
network tested at 2Mbps data rate (with 500kbps arbitration). Waveforms clearly demonstrated RXD without any
errors. Even though bus common mode VCM movement occurred during the frame for heterogeneous condition,differential bus and RXD waveforms remained undisturbed and comparable to all 5V homogeneous network
conditions.
Below are two waveforms during arbitration for homogeneous (all 5V nodes) and heterogeneous (three
TCAN340x-Q1 and 8 standard 5V CAN nodes) 11-node complex triple star network tested at 2Mbps data rate(with 500kbps arbitration). Waveforms clearly demonstrate RXD is received without any errors. Even though bus
common mode VCM movement happens during the frame for heterogeneous condition, differential bus and RXD
waveforms remain undisturbed and comparable to all 5V homogeneous network condition.

Figure 4-1. 5V Homogeneous Network CAN FD Frame Waveform

Figure 4-2. 3.3V and 5V Heterogeneous Network CAN FD Frame Waveform

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5 EMC of TCAN340x-Q1
As stated in previous sections, meeting component level EMC is a strict requirement to get CAN transceiverqualified at major car makers. One standard that is used to test and qualify CAN transceivers for EMC is
IEC62228-3:2019. This standard tests CAN transceivers for conducted emissions and conducted immunity in a
two-node setup, and for ISO10605 ESD and pulse transients.
CAN being a differential interface, electromagnetic energy due to differential signals largely gets canceled
out, but any common mode mismatch can show up on cable harnesses and result in significant system levelemissions. To meet EMC, significant design effort has been made in TCAN340x-Q1 to keep switching symmetry
between CANH and CANL during rising and falling bus transitions. Additionally, proprietary design techniques
are implemented in TCAN340x-Q1 that dynamically adjusts the bus common mode while driving and receiving
CAN data to meet emissions specifically in heterogeneous networks. Emissions in homogeneous network(where all nodes on CAN bus are 3.3V) is easier to meet compared to the stricter heterogeneous network (mix of
3.3V and 5V CAN node on same bus) because of the movement of common mode during recessive condition.
TCAN340x-Q1 meets strict EMC requirements per IEC 62228-3:2019 under both homogeneous andheterogeneous network conditions and passing reports are available upon request.

6 Benefits of TCAN340x-Q1 over competition 3.3V CAN offerings
Table 6-1. Feature Comparison of TCAN340x-Q1 Against Competition 3.3V CAN Devices
Parameter

Competition A

Competition B

Competition C

TCAN340x-Q1

No

No

No

Yes

Only TI is automotive qualified

Automotive qualified

System Implication

EMC certified

No

No

No

Yes

Only TI is automotive EMC certified

CAN bus standoff

±36V

±40V

±60V

±58V

TI is able to work for 12V and 24V
automotive battery sub-systems

Receiver common
mode voltage range

±25V

±25V

±36V

±30V

TI has extended operating common
mode range

Maximum data rate

1Mbps

5Mbps

4Mbps

8Mbps

Operation guaranteed to CAN FD
data rates and beyond

Supply current
standby mode

600μA

60μA

NA

17μA

Lower standby current consumption
reduces battery voltage drain

7 Conclusion
TI’s EMC-certified 3.3V CAN transceiver TCAN340x-Q1 offers a compelling alternate to automotive designers
against a standard 5V CAN transceiver. It is footprint compatible, and fully interoperable with 5V CAN
transceivers while being compatible with physical layer ISO11898-2:2024 specifications. TCAN340x-Q1 helps
reduce CAN solution cost by 25% (eliminates automotive 5V LDO) and PCB space by 70%. TCAN340x-Q1
marks the beginning of a new era in 3.3V CAN FD transceivers helping to remove the 5V supply rail traditionallyneeded in an application only for the 5V CAN transceiver and reducing the BOM cost and PCB size.

8 Revision History
NOTE: Page numbers for previous revisions may differ from page numbers in the current version.
Changes from Revision * (June 2024) to Revision A (July 2024)
Page• Updated Section Abstract...................................................................................................................................1• Updated Section 1.............................................................................................................................................. 2• Updated Section 2.............................................................................................................................................. 4• Updated Section 3.............................................................................................................................................. 5• Updated Section 4.............................................................................................................................................. 6• Updated Section 7.............................................................................................................................................. 88

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