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Advanced PCB design and the inhibition of total resistance
Advanced PCB design and the inhibition of total resistance

Total resistance interference is caused by PCB on a lot of ground. When two or more circuits share a ground, the different loop current in the common ground line a certain pressure drop, the drop will affect the circuit performance by amplification; when the current frequency is high, it will produce very leaving large circuit inductance interference.

Total impedance to suppress interference, use the following measures:

(1) that the circuit ground to the same level of several cell sites try to focus on access in order to avoid channeling other people ac signal circuit of the level, or the level of the ac signal to go he went to the other circuits. Signal frequency for the low-frequency circuit is less than 1MHZ, if the working frequency used in a bit of a 1OMHz and grounded, the ground wire length should not exceed the wavelength of 1 / 20. In short, a little common ground impedance grounding is to eliminate interference with the basic principles.

(2) multi-point ground near a large public ground on the PCB distribution of the edge of the plate, and the present semi-closed loop (anti-magnetic interference), at all levels of the circuit to the nearest ground to prevent ground too long. Signal frequency for high frequency circuit is greater than lOMHz.

(3) The bus ground bus is made of silver-plated copper plate, PCB ground all the ICs on the bus are received. Symmetric strip transmission line bus with the low impedance characteristics, in the high-speed circuit can improve the signal transmission speed and reduce interference.

(4) large areas of ground in the high frequency circuit area will not have all the PCB layout for the ground to reduce the inductance in the ground, thus weakening the ground generated by high-frequency signal line, and played the electric field disturbance shielding effect.

(5) Bold if the ground is very thin ground wire, ground potential is with the current changes, resulting in electronic equipment, the timing signal level instability, anti-noise performance deterioration, and its width should be at least greater than 3mm.

(6) D / A (D / A) an electrical circuit separate from the two separate electrical circuit, and then were connected with the supply-side ground to suppress their mutual interference.


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