In modern industrial control and automotive electronic systems, CAN-bus has become the preferred communication protocol because of its high reliability and real-time performance. However, many engineers often neglect a key link in actual deployment - the physical medium selection of bus wiring.
Have you ever experienced communication interruptions, signal errors, or poor system stability? There is an easily overlooked factor behind it: the type and layout of cables.
In fact, the performance of the CAN bus is highly dependent on the correct use of twisted pairs. We will deeply discuss the irreplaceability of twisted pair in CAN network, from basic principle to practical application, and step by step reveal how it becomes the "guardian" of communication stability in high-speed and high-interference environments.
What is Twisted Pair?
Twisted pair refers to a kind of universal wiring made of two mutually insulated wires twisted together according to certain specifications. The main function of twisted pair is to prevent external electromagnetic interference and reduce the external interference of its own signal.
The principle is that two insulated wires are twisted together, and the interference signal acting on the two wires twisted together is consistent (this interference signal is called common-mode signal). The common-mode signal can be eliminated in the differential circuit receiving the signal, so as to extract the useful signal (differential-mode signal).
Why Does the CAN Bus Have to be Twisted Pair?
Ninety percent of CAN-bus failures are due to physical layer design flaws - when your control system has frequent signal errors or communication interruptions, the problem may be hiding in a neglected cable layout.
In the field of automotive electronics and industrial control, CAN-bus has become the core communication protocol by virtue of its real-time and multi-master architecture (single node failure does not affect the overall network).
Common Twisted Pair and Its Advantages
Common twisted-pair cables are Category 3, Category 5 and Category 5e, as well as the latest Category 6. The former has a thin diameter and the latter has a thick diameter.
- Category 5 cable: This type of cable increases the winding density and is coated with a high-quality insulating material. The transmission rate is 100MHz.
- Category 5e cable: Category 5e line has small attenuation, less crosstalk, higher ACR and Structural Return Loss, and smaller time delay error.
- Category 6 cable: The transmission frequency of this type of cable is 1MHz ~ 250MHz, and provides twice the bandwidth of Category 5e.
Twisted Pair Types
Twisted pair is currently divided into unshielded twisted pair (UTP) and shielded twisted pair (STP). Shielded twisted-pair cables are wrapped in aluminum and platinum to reduce radiation, but they do not completely eliminate radiation.
Combination of CAN and Twisted Pair
Controller Area Network (CAN) is a serial communication protocol bus used in real-time applications, and it is one of the most widely used field buses in the world.
When CAN is applied to new energy vehicles, it means that it has to work in a serious electromagnetic environment, so how to resist interference is the most concerned topic for engineers. When the CAN bus uses twisted pair, it can solve these interference problems very well.
The CAN interface uses differential signal transmission mode. Differential signaling is a method of transferring information using two complementary electrical signals. Taking high-speed CAN as an example, different logic States are transmitted through CANH and CANL signal lines, and the receiving circuit only identifies the signal difference between the two signal lines.
Twisted Pair: A Gene-Level Solution for Electromagnetic Compatibility
1. Analysis of Triple Anti-jamming Mechanism
- Differential signal enhancement: Two insulated conductors are twisted around each other at a precise pitch to form a natural electromagnetic cancellation structure
- Common-mode noise suppression: External interference generates equal-amplitude noise on both lines, which is automatically cancelled by the differential circuit
- Radiation self-suppression: The twisted structure reduces the crosstalk between cables
2. Automotive Electronic Cable Selection Guide
| Type | Transmission Frequency | Maximum Speed | Applicable Scenarios | Anti-interference Level |
|---|---|---|---|---|
| CAT5e UTP | 100MHz | 1Gbps | Body comfort system (LIN subnet) | ★★☆ |
| CAT6 STP | 250MHz | 10Gbps | Power CAN for new energy vehicles (recommended) | ★★★★ |
| CAT7 SF/FTP | >600MHz | 40Gbps | Autopilot domain controller | ★★★★★ |
Future Evolution: Twisted Pair Technology in the Gigabit Era
A new generation of solutions is emerging as the volume of intelligent driving data explodes (LIDAR generates 2GB of data per second):
- Composite shielding structure: Star twist + aluminum-magnesium alloy mesh (anti-bending fatigue)
- Adaptive lay length: AI dynamically adjusts lay length to compensate for temperature distortion
- Fiber CAN: CAN FD over Fiber breaks the 200 m distance limit
We can clearly see that twisted pair is much more than "two wires twisted together" - it is the cornerstone of CAN bus to maintain stable communication in high interference environment.
From resisting common-mode noise to enhancing signal integrity, from the choice of category to the design of shielding, every detail directly affects the reliability of the whole system. Especially in high-standard applications such as automotive electronics and industrial automation, the correct selection and arrangement of twisted pair is often the key to distinguish robust operation from frequent failures.
Optimize Your CAN Bus System Today
Learn how to implement the most reliable twisted pair solutions for your automotive or industrial control systems. Download our comprehensive guide to CAN bus wiring best practices.
Get Free GuideFrequently Asked Questions
Electric vehicles have complex electromagnetic environments with high-power components like motors and inverters. Twisted pair cables provide essential noise immunity through differential signaling and common-mode noise rejection, ensuring reliable communication between critical vehicle systems.
Shielded twisted pair (STP) has an additional conductive layer that provides extra protection against electromagnetic interference. Unshielded twisted pair (UTP) is less expensive and easier to install but offers less protection. For high-interference EV environments, STP is generally recommended.
The twist length (or pitch) determines how effectively the cable rejects electromagnetic interference. Smaller pitch (tighter twists) provides better noise immunity but increases cable capacitance. Optimal twist length balances interference rejection with signal integrity requirements for the specific application.
Yes, standard CAT5e or CAT6 Ethernet cables can be used for CAN bus since they are twisted pair cables. However, for automotive applications, you should use cables rated for automotive environments with proper temperature, vibration, and chemical resistance specifications.