Countermeasures for Crosstalk

Crosstalk noise is induced by capacitive or inductive coupling between two adjacent transmission lines that run in parallel (called an aggressor and a victim). Regarding crosstalk, care should be exercised as to rapidly rising or falling signals. When such a signal travels through a transmission line, crosstalk noise is induced in an adjacent line (victim) and propagates in both directions: in the same direction as for the aggressor signal and in the direction opposite to it.
Since the speed of crosstalk propagation is equal to that of the aggressor signal, the crosstalk noise that travels in the same direction as the aggressor signal (called far-end crosstalk) appears as pulse-like noise.
On the other hand, the crosstalk noise that travels in the opposite direction (called near-end crosstalk) maintains a constant level while the aggressor signal propagates along the line.
Crosstalk noise also propagates along the aggressor line and then returns to the victim line.
Generally, you can prevent crosstalk as follows.

Countermeasures for crosstalk

Measures for Crosstalk:

  • Add earth traces between parallel traces. (Alternatively, use a multi-layer board in which a low-impedance layer (e.g., VCC or GND layer) lies between signal layers.)
  • Reduce the length of traces that run in parallel.
  • In the case of a multi-layer board, run traces on alternate layers  orthogonally to each other (See the right hand side figure).
  • Increase the spacing between traces.
Countermeasures for crosstalk

The below figure shows a typical level of crosstalk noise traveling along 30-cm traces.
This example shows near-end crosstalk. When the near end of the victim trace is the receiving end, it is susceptible to the effect of crosstalk.

Usage Considerations of CMOS Logic ICs

Handling of Unused Input Pins
Input Rise and Fall Time Specifications
Multiple Outputs from a General-Purpose CMOS Logic IC Come Into Conflict (Short-Circuiting)
Connecting a Load Capacitance to a CMOS Output Pin
Calculating the Operating Supply Current and Power Dissipation
Level Shifting Using an Input-Tolerant Function
Example of Application of the Power-Down Protection Function (Partial Power-Down)
Input-Tolerant and Output Power-Down Protection Functions Available with Each Series
Types of Noise to be Noted
Countermeasures for Reducing Switching Noise
Countermeasures for Signal Reflection
Countermeasures for Hazards
Countermeasures for Metastability
Countermeasures for Latch-Up
Countermeasures for ESD Protection


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