In terms of this property, the differential signal's anti-interference ability can reduce ground bounce noise and power plane sliding.ĭue to the existence of the power wire and the ground wire, when multiple digital signals on the PCB are switched synchronously (such as the CPU data bus, address bus, and so on), transient load current flows from the power supply into the circuit or from the circuit into the ground wire. As a result, both ground reference plane disturbance and signal path interference are equally essential. The logic gate responds to the input pin and the designated reference pin, and we don't know which one is which (for TTL, it's usually a negative power supply for ECL, it's usually a positive power supply, but not all of them). The difference between the incoming signal and its logical ground reference plane triggers the single-point termination circuit. The logic gate responds to the difference between the input signal and the reference pin, rather than the absolute input signal. The frequency of the signal is proportional to the frequency of the noise. The signal frequency is equal to the noise frequency created by the current flowing through the copper-clad plane.
A closed-loop is formed by the current on the signal line. There is always a return current in the opposite direction when current starts from the signal driver, flows through the signal line and is injected into the signal receiving end: starting from the ground pin of the load, passing through the copper plane, flowing to the signal source, and flowing through the signal receiving end. Select the path with the lowest impedance for low-frequency signal return and the path with the lowest inductance for high-frequency signal return. High-frequency frequencies and low-frequency signals have various return routes. Ground and power planes are typically used to complete the reflow in digital circuits. It is actually a method of charging the dielectric capacitor sandwiched between the transmission line and the DC layer for high-frequency signal transmission.
As a result, current flows in the loop at all times, and any signal in the circuit exists as a closed-loop. The fact that electrons never stay in one place and must return no matter where the current runs are one of the properties of electron flow. In actuality, the signal is conveyed by current, specifically the movement of electrons, according to basic circuit theory.
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As a result, many digital engineers believe the loop path is unrelated.Īfter all, both the driver and the receiver are voltage-mode devices, so why take current into account? It appears to be flowing in only one way. The signal is sent over a wire from the output to the receiving end. A digital signal propagates from one logic gate to the next in the schematic layout of a digital circuit.
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