Hello, my name is Taro.
This time, I would like to write about LVDS (Low voltage differential signaling).
Outline of LVDS
LVDS is a type of differential signal interface.
There are various standards for differential signaling, each with different amplitude values and termination methods.
The advantages of differential signals include the following
・ Low power consumption due to small voltage swing on the wiring
・ Low EMI due to low field emission on the differential wiring
・ Low amplitude allows for higher speeds
・ Noise immunity because it sees the difference between two signals
The disadvantages are that two wires, one positive and one negative, are required and that the lengths of these two wires must be equal.
Two Differential Signal Amplitude Measurement Methods
There are two methods for measuring the amplitude of differential signals: Single-Ended and Differential.
Single-Ended indicates the difference in voltage between the two signals actually output. In datasheets, it is sometimes referred to as Vpp.
Differential, on the other hand, is the voltage value of the Positive signal minus the voltage value of the Negative signal. In datasheets, it is sometimes written as Vdiff.
The difference between Single-Ended and Differential is not clear from the words alone (laugh).
Below is a diagram of the difference between Single-Ended and Differential.
As you can see, the amplitude of a differential signal differs depending on the measurement method.
Note on Differential Signal Amplitude
As shown in the figure above, we now know that the values differ between the two amplitude measurement methods, but when should we be careful?
It is necessary to pay attention when reading the datasheet.
For example, when we look at the electrical characteristics of the differential input voltage of a device, we must pay attention to which value is indicated.
In some cases, the electrical characteristics may not be met.
Also, for Slew Rate, you must be careful about whether Single-Ended or Differential measurement method is described in the datasheet.
In some cases, it may not be possible to observe timing constraints.
You need to be careful about many things, but that's when our technical support comes in!
Once again, thank you for your continued support.
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