How a $20 Cable Cost Us $100K—and What You Can Learn from It
A few years ago, I was deeply involved in environmental testing for a new product. The setup was straightforward: a 100-meter cable connected our test board—placed near a radiation source—to a control system in a safe room. We ran initial checks. Everything looked perfect. Then we started the test. Boom! Catastrophic failure. The board was toast. We replaced it. Reran the test—another failure.
Five boards and a painful amount of money later, we finally found the culprit: a tiny fray in the 100-meter cable. Every time we moved the setup, the cable shifted just enough to cause an intermittent short between the data and power lines. That $20 cable? It cost us $100,000 in damages and wasted test time.
The lesson? Faults like this are more common than you think—and they’re almost always preventable.
The Sources of a Networking Fault
RS-485 and CAN transceivers have been the backbone of industrial communication for decades. As these systems are deployed in increasingly harsh environments, the risk of faults grows. High-voltage power lines often share conduits with data cables, and even minor physical damage can lead to major failures. Figure 1 shows just a few of the things that a network cable might be subjected to during its operation.
Figure 1: Potential Faults in Common Networking Environments
A “fault” occurs when a high voltage unintentionally comes in contact with one or both of the cable data lines in an RS-485 or CAN network. Without special protection, these faults would damage the communication transceivers, leaving the channel inoperable and requiring the replacement of not only the cable but the nodes connected to it as well.
- PCB Defect: Even with a well-designed PCB, defects can occur, and if that defect is a solder mask error that shorts the receiver inputs to the supply, then a fault could occur.
- Solder Bridge: During board assembly, solder bridge errors can occur. An example could be a solder bridge causing a short on the cable connector itself, which could cause a high-voltage fault.
- Lightning Strike/Surge: A nearby or direct lightning strike can cause a power surge to traverse the cable, which will damage any unprotected circuitry.
- Crushed Cable: Heavy equipment can damage cables sheathing causing wire shorts if set on top of the cable.
- Kinked Cable: If a cable is bent past its minimum radius, then damage can occur, resulting in a high voltage short.
- Jacket Fray: Cables that see repetitive motion can degrade to the point of shorting wires inside the jacket as the jacket frays.
- Miswiring: Human error during installation can connect high voltage to sensitive data lines.
The Case for Built-In Fault Protection
You can add discrete protection—transient voltage suppression (TVS) diodes, current limiters, and clamps—to your board. But that takes up space, adds cost, and still might not be enough for sustained faults.
That’s why Analog Devices (ADI) has developed RS-485 and CAN transceivers with integrated fault protection. These devices are designed to survive real-world abuse—without external components.
The following transceiver products bring best in class integrated fault protection all in one small package:
- MAX13448E: Full-Duplex, 5 V, ±80 V Fault-Protected RS-485 Transceiver
- MAX14775E/MAX14776E: Half-Duplex, 3.3 V to 5 V, ±65 V Fault-Protected RS-485 Transceiver
- MAX3050/MAX3057: –5 V, 2 Mbps ±80 V Fault-Protected CAN Transceiver
- LTC2875: 3.3 V or 5 V, 4 Mbps ±65 V Fault-Protected CAN Transceiver
These parts don’t just survive faults—they manage them intelligently.
What Happens During a Fault?
Take the MAX14776E as an example. When a fault is detected—say, 65 V hits the A pin—the transceiver disables its A/B pins to prevent damage. After a 300 ms timeout, it checks again. If the fault is gone, it resumes normal operation. If not, it stays in high-impedance mode and retries every 300 ms.
In lab tests, this part handled repeated faults without a scratch. A clock signal was applied to DIN (dark blue trace), and the RO pin was monitored (cyan trace) in a loopback setup. Even with 65 V applied to the data line (pink trace), the transceiver protected itself and kept the system running.
Figure 2: Fault Protection Demonstrated with the MAX14776E
Don’t Let a Fault Take Down Your System
Faults are inevitable. But failure doesn’t have to be. With robust, fault-protected transceivers from ADI, you can design systems that survive the unexpected—whether it’s a frayed cable, a lightning strike, or a miswired connector. Don’t let a $20 mistake cost you $100K. Build smarter. Protect your network. ADI has your back.
See the blogs in the TranscendingConventionalFieldBus series.