1. The effect of the electrostatic field before electrostatic discharge.
2. The charge injection effect caused by the discharge.
3. The field effect produced by the electrostatic discharge current.
However, it mainly affects the third effect. The following discussion will give a design guide to the problem described in Article 3.
In general, the field coupling originating from the receiving circuits can be reduced in one of the following ways:
1. Use a filter at the source to attenuate the signal.
2. Use a filter at the receiving end to attenuate the signal.
3. Increase the distance to reduce coupling.
4. Reduce the antenna effect of the source and / or receive circuitry to reduce coupling.
5. Place the receive antenna perpendicular to the transmit antenna to reduce coupling.
6. Shield between the receiving antenna and the transmitting antenna.
7. Reduce the impedance of the transmit and receive antennas to reduce electric field coupling.
8. Increase the impedance of one of the transmit or receive antennas to reduce magnetic field coupling.
9. Use a consistent, low-impedance reference plane (as provided by the multilayer PCB design) to couple the signals so that they remain in common mode.
In specific PCB designs, such as electric or magnetic fields dominate, application methods 7 and 8 can be solved. However, electrostatic discharge generally produces both an electric field and a magnetic field, which indicates that method 7 will improve the immunity of the electric field, but at the same time reduce the immunity of the magnetic field. Method 8 is the opposite of the effect of Method 7. Therefore, methods 7 and 8 are not perfect solutions. Regardless of whether it is an electric field or a magnetic field, methods 1 to 6 and 9 will achieve certain effects, but the PCB design solution depends mainly on the combined use of methods 3 to 6 and 9.
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