Volkswagen VW TL 823 66 Combined Interference in Sensor Cables

The VW TL 823 66 standard, developed by the Volkswagen automotive company , defines a test method for determining the combined noise level in sensor wiring found in vehicles.

Essentially, there are three different levels of electromagnetic compatibility (EMC) in vehicles:

• Vehicle level. This is mostly not about chip development.
• Electronic control unit (ECU) level. Partially relevant for chip development.
• Component/chip level. This is the most important part for chip designers. Further measurements are required to ensure electromagnetic compatibility.

Unwanted electromagnetic connection is troublesome. It can cause electromagnetic interference, both external and internal interference and interference in electronic circuits. In an interference electromagnetic connection, source components transmit or emit electromagnetic signals to interfere with components in the same circuit or neighboring circuit. In low frequency circuits, the effects of unintentional electromagnetic coupling are comparatively less than in microwave and radio frequency circuits.

Electromagnetic interference can be from a radiated signal or from a transmitted signal, depending on the coupling. Before designing reduction or protection methods, it is necessary to know the electromagnetic coupling types:

• Radiated coupling: In the radiating coupling, the source and receiver or victim are separated by a distance. The source and victim are more like radio antennas. The electromagnetic signal emitted by the source is received by the victim and interferes with the normal operation of the victim and the circuit in which it is placed.
• Conducted coupling: Conducted coupling and interference occur when there is a path for unintentional electromagnetic signals to travel between the source and the victim. Transmission lines are the main transmission paths in electronic circuits.
• Capacitive coupling: The coupling capacitance between source and victim is the reason behind capacitive coupling. Electromagnetic disturbances depend on coupling capacitance and voltage variations.
• Inductive coupling: When components of a circuit are magnetically coupled, it is a form of inductive coupling. Parasitic inductance plays an important role in the inference caused by inductive coupling.

With the test method described in the VW TL 823 66 standard, the combined interference level in the sensor cables in the vehicles is determined.

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