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# Some basic concepts of signal integrity in high speed circuit design

Posted:03:44 PM November 05, 2018 writer: G

2. Transmission Line: A connection line consisting of two conductors of a certain length, which we call a transmission line, sometimes called a delay line.

3. Lumped circuit: In general circuit analysis, all parameters of the circuit, such as impedance, capacitive reactance, and inductive reactance, are concentrated at various points in space. On each component, the signal between each point is Instantly delivered, this idealized circuit model is called a lumped circuit.

4.Distributed System: The actual circuit situation is that various parameters are distributed throughout the space where the circuit is located. When the signal delay time caused by this dispersion is not negligible compared with the change time of the signal itself, Hou, the entire signal channel is a complex network with resistors, capacitors, and inductors. This is a typical distributed parameter system.

5. Rise/Fall Time: The time it takes for the signal to transition from low to high, usually the duration of the rising/falling edge between 10% and 90% of the voltage amplitude, recorded as Tr.

6. Knee Frequency: This is the frequency range (0.5/Tr) that characterizes most of the energy in a digital circuit. It is denoted as Fknee. It is generally believed that energy exceeding this frequency has no effect on the transmission of digital signals.

7. Characteristic Impedance: Each step in the propagation of an AC signal on a transmission line encounters a constant instantaneous impedance called a characteristic impedance, also known as a surge impedance, denoted as Z0. It can be expressed by the ratio of the input voltage to the input current (V/I) on the transmission line.

8. Propagation delay: refers to the propagation delay of the signal on the transmission line, which is related to the line length and the signal propagation speed, and is recorded as tPD.

9. Micro-Strip: A transmission line in which only one side has a reference plane.

10. Strip-Line: A transmission line with reference planes on both sides.

11. Skin effect: When the signal frequency increases, the flow charge will gradually approach the edge of the transmission line, and even no current will pass in the middle. Similar to this is the clustering effect, in which the current-intensive area is concentrated on the inside of the conductor.

12. Reflection: refers to the incomplete absorption of signal energy due to impedance mismatch. The degree of emission can be expressed by the reflection coefficient ρ.

13. Over shoot/under shoot: Overshoot means that the first peak or valley of the received signal exceeds the set voltage—for the rising edge, the first peak exceeds the maximum voltage; The edge means that the first valley exceeds the minimum voltage, and the undershoot is the second valley or peak.

14. Oscillation: In one clock cycle, repeated overshoot and undershoot occur, which we call oscillation. The oscillation can be divided into ringing and surrounding oscillation according to the expression form, the ringing is an underdamped oscillation, and the ring is an overdamped oscillation.

Termination: The effect of achieving impedance uniformity by adding a resistor or a capacitor device in order to eliminate reflection. Because it is usually used at the source or terminal, it is also called termination.

15. Crosstalk: Crosstalk is the undesired voltage noise interference caused by electromagnetic coupling to adjacent transmission lines when the signal propagates on the transmission line. This interference is caused by the mutual inductance and mutual capacitance between the transmission lines.

Return current: Refers to the return current that propagates with the signal.

16. Self shielding: When a signal propagates on a transmission line, a method of suppressing an electric field by a large capacitive coupling and a small inductive coupling to suppress a magnetic field to maintain a low reactance is called self-shielding.

17. Forward Crosstalk: refers to the first interference generated by the interference source to the receiving end of the victim source, also known as Far-end crosstalk.

18. Forward Crosstalk: refers to the first interference generated by the interference source to the sender of the victim source, also known as Near-end crosstalk.

19. Shielding efficiency (SE): A parameter that evaluates the suitability of shielding in decibels.

Absorption loss: Absorption loss is the amount of energy loss when electromagnetic waves pass through the shield.

20. Reflection Loss: Reflection loss refers to the amount of energy loss due to internal reflection of the shield, which varies with the ratio of the wave resistance to the shield impedance.

21. Correction factor: A parameter indicating a case where the shielding efficiency is lowered. Since the absorption efficiency of the shield is not high, the internal re-reflection increases the energy passing through the other side of the shield layer, so the correction factor is a negative number and is used only for thin Analysis of the presence of multiple reflections in the shield.

22. Differential Mode EMI: The EMI generated by the coupling between the current flowing from the driving end and the receiving end of the current on the transmission line is called differential mode EMI.

23. Common Mode EMI: When two or more transmission lines are output from the driver to the receiver in the same phase and direction, common mode radiation is generated, which is common mode EMI.

24. Transmit Bandwidth: The highest frequency transmit bandwidth. When the digital integrated circuit switches from logic high and low, the square wave signal frequency generated at the output is not the only component that causes EMI. The square wave contains a wider range of sinusoidal harmonic components, which are the EMI frequency components that engineers care about, and the highest EMI frequency is also known as the EMI emission bandwidth.

25. Electromagnetic environment: The sum of all electromagnetic phenomena present at a given location.

26. Electric: An electromagnetic phenomenon that can cause a decrease in the performance of a device, equipment, or system or damage to a living or inanimate matter.

27. Electromagnetic Interference: Electromagnetic disturbances cause degradation in equipment, transmission channels, and system performance.

28. Electromagnetic compatibility: The ability of a device or system to function properly in an electromagnetic environment without posing unacceptable electromagnetic disturbances to anything in the environment.

29. Intra-system interference: Electromagnetic interference caused by electromagnetic disturbances within the system occurs in the system.

30. Intersystem interference: Electromagnetic interference caused by electromagnetic interference generated by other systems to a system.

31. Electrostatic discharge: A charge transfer caused by objects having different electrostatic potentials approaching or contacting each other.

Setup Time: The setup time is the time that the receiving device needs data to be stable on the input before the clock edge.

32. Hold Time: In order to successfully latch a signal to the receiver, the device must require the data signal to remain asserted for a period of time after being triggered by the clock edge to ensure that the data is properly manipulated. This minimum time is what we call retention time.

33. Flight Time: It refers to the delay between the signal transmitted from the driver to the receiver and reaching a certain level, which is related to the transmission delay and rise time.

34. Tco: refers to the time difference between the input clock edge of the device and the effective time of the output signal. This is the sum of all delays of the signal inside the device, which generally includes logic delay and buffer delay.

Buffer delay: The time required for a signal to pass through a buffer to achieve a valid voltage output.

35. Clock Jitter: Clock jitter is the random error of the clock trigger edge. It can usually be measured by the difference between two or more clock cycles. This error is generated internally by the clock generator, and later. The wiring does not matter.

36. Clock Offset (Skew): refers to the difference in delay between multiple subclock signals generated by the same clock.

False clock: A false clock is when the clock crosses the threshold unconsciously to change state (sometimes between VIL or VIH). Usually caused by excessive undershoot or crosstalk.

37. Power Integrity: Refers to the quality of the power and ground in the circuit system.

38. Simultaneous Switch Noise: refers to the instantaneous change of current (di/dt) when the device is in the switching state. When the inductance is present on the return path, an AC voltage drop is formed, causing noise, referred to as SSN. . Also known as Δi noise.

39. Ground Bounce: refers to the fluctuation of the ground plane caused by the package inductance, resulting in inconsistency between the ground and the system. Similarly, if the difference between the chip and the system power caused by the package inductance is called Power Bounce.

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