Termination resistor

・In Japanese

■What is a terminating resistor?

A termination resistor is used to reduce the signal reflected at the end of a communication cable, mainly when performing digital communication that handles high frequencies. The following is an example of using a terminating resistor in a CAN(Controller Area Network) communication system. A termination resistor is attached to the ECU(Electronic Control Unit) connected by the main bus.

■Reflection of communication signal

Reflection is a phenomenon in which when the end of a transmission line is open, the open end acts like a reflector and reflects a signal. When detecting a signal, this reflection becomes noise and it becomes impossible to detect correct information. Adding a resistor to this end suppresses reflections as the resistor is responsible for consuming energy.



The image of the waveform when reflection is occurring is as follows. What was originally a square wave signal is vibrating due to the influence of reflection. This vibration waveform is called ringing.

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