SLLA636 June   2024 TCAN3403-Q1 , TCAN3404-Q1

 

  1.   1
  2.   Abstract
  3.   Trademarks
  4. 1Introduction
  5. 25V CAN Transceiver
  6. 3TI's TCAN3403-Q1, TCAN3404-Q1 3.3V CAN FD Transceivers
  7. 4 Interoperability (IOPT) of TCAN340x-Q1
  8. 5 EMC of TCAN340x-Q1
  9. 6 Benefits of TCAN340x-Q1 over competition 3.3V CAN offerings
  10. 7 Conclusion

1 Introduction

With the electrification of vehicles happening at a rapid pace, multiple ECU’s are deployed all through the vehicle. These sub-systems talk to each other via CAN network.

Figure 1-1 shows a CAN network.

Typical CAN Network 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 embedded CAN protocol controller and power device (DC-DC converter or Linear regulator) that converts automotive battery voltage to 5V. Additionally, in case the MCU/MPU I/O voltage is 3.3V, separate 3.3V power device is used on ECU PCB. Figure 1-2 shows a simplified schematic.

Application Schematic of a 5V CAN Transceiver Figure 1-2 Application Schematic of a 5V CAN Transceiver

Typical CAN bus signals consist of dominant and recessive phases. CAN driver produces differential signal of at least 1.5V across a 60Ω load during the dominant phase, whereas the driver weakly biases the bus to common mode 2.5V level during the recessive phase. This signaling is designed for bitwise arbitration and device with highest priority ID (CAN frame Identification field with most dominant bits) takes control of the bus since dominant (strong drive) is able to overcome recessive (weak biasing). The receiving nodes monitor CANH-CANL differential signal and are able to decode the CAN message, as long as the signal is above 900mV (dominant threshold) or below 500mV (recessive threshold).

CAN Signaling, Diver and Receiver Representation Figure 1-3 CAN Signaling, Diver and Receiver Representation

VD = VCANH – VCANL

For driver: VOD(DOM) ≥ 1.5V @ 60 Ω load

For receiver: VID(DOM) ≥ 900mV, VID(rec) ≤ 500mV

CAN wiring harness is spread throughout the vehicle. Any common mode disturbance generated by CAN transceiver can result in emissions that can impact functionality of other automotive sub-systems. Similarly, the harness is susceptible to pick-up electromagnetic interference from other modules. Thus, electromagnetic compliance is a key requirement for any automotive CAN transceiver. Additionally, different sub-systems can have CAN transceivers from different semiconductor vendors, and hence interoperability is another strict requirement needed for any CAN transceiver to be used in mainstream vehicle network.