Single-ended and differential signaling: Two options for in-vehicle networking IVN applications
In-vehicle networking (IVN) is experiencing strong growth due to the increase of complex capabilities in next-generation transportation applications and the rapid advancement of technology. What’s linking all these advanced systems are the signaling cables, namely single-ended signaling and differential signaling.
There are many pros and cons to single-ended and differential signaling technologies, each has different strengths for specific applications. A few questions to consider early in the design process:
- How does each solution maintain signal integrity (SI)?
- What precautions need to be made for electromagnetic interference (EMI) and electromagnetic compatibility (EMC)?
- What reasonable performance parameters can be expected from an assembly of each category (single-ended (coax cable terminated with coax connectors on both ends of the cable) and differential (shielded-twisted pair or shielded-parallel pair with fully shielded differential connectors on both ends of the cable)?
Definition of terms: Single-ended and differential signaling
Single-ended signaling: Is the simplest and most commonly used method of transmitting electrical signals over wires. One wire carries a varying voltage, representing the signal, while the other wire is connected to a reference voltage, known as the ground.
Differential signaling: Is a method for electrically transmitting information using two complementary signals. This technique sends the same electrical signal as a differential pair of signals, each in its own conductor. The pair of conductors can be wires in a twisted-pair, a ribbon cable or traces on a printed circuit board (PCB).
Pros and cons of single-ended and differential signaling
Increasing demand and legislation requiring greater vehicle functionality and advanced driver assistance systems (ADAS) is multiplying complex electronics in vehicles because of electronic control units (ECUs). The latest automotive in-vehicle networks contain more devices and components than ever before to produce, transmit and receive data at higher rates. With this growth and broad array of applications to support from the channel perspective, the primary question remains, which is better single-ended solutions or differential solutions?
Pros of Single-ended technology:
- Relative lower cost
- Easier to install
- Good EMI shielding
Cons of Single-ended technology
- Noise rejection
- Higher voltages required to reduce signal-to-noise ratio (SNR)
Pros of Differential technology
- Good common noise reduction
- Lower signaling voltages, more stable signals
- Longer distances vs. noise, better performance over long distances
Cons of Differential technology:
- Symmetrical electrical signal is critical, unbalance system can create EMI
- Two pins
- Relative higher cost
Use Cases
Common transportation applications and recommend signaling technology:
| Applications/Use cases | Single-ended | Differential |
|---|---|---|
| Cameras (100M/1G) | X | |
| Video displays (16Gbps) | X | |
| Ethernet (100M/1G/2.5G/5G/10G/10G+) | X | |
| Sensors - lidar/radar (100M - 2.5G) | X | |
| Antennas (up to 20Gbps) | X |
Conclusion
Learning the pros and cons of each signaling technology will allow for the delivery of optimal solutions in terms of relative cost, performance, and ease of implementation. Both technologies deliver solid benefits depending on the application.
“Picking the right technology for your application should be based on what is critical in terms of the application characteristics of the channel, including EMI/EMC performance, link length, common mode noise rejection, and communication technology.”
Harsh Patel, signal integrity engineering supervisor, Molex.
Avnet’s own Jason Struble, transportation supplier manager, and guest technology partner, Harsh Patel, signal integrity engineering supervisor from Molex, recently held an in-depth discussion of single-ended and differential signaling. Their recorded webinar compared and contrasted the two competing technologies along with a broad range of related topics. Gain further insights by watching the webinar: Watch the complete webinar by Avnet and Molex.
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