Mobile circuit board design techniques: methods to improve audio performance

Date：

2017-01-05

Source：

Mobile phone circuit board design to improve the audio performance should be:

Carefully consider the underlying plan. The ideal underlying plan should divide the different types of circuits into different areas.

Use differential signals whenever possible. Audio devices with differential inputs can suppress noise. Differential signal in the middle of the general can not add ground. Because the application of differential signals is the most important point is the use of differential signals between the benefits of coupling, such as magnetic flux elimination, anti-noise ability. If the ground wire in the middle, it will destroy the coupling effect.

Differential pairs of wiring there are two points to note that the length of the two lines should be as long as possible, the other is the distance between the two lines (this distance determined by the differential impedance) to remain the same, that is, to keep parallel. There are two parallel ways, one for the two lines walk in the same line layer (side-by-side), one for the two lines in the upper and lower adjacent two layers (over-under). Generally in front of the side-by-side to achieve more ways.

Isolate the ground current to avoid the digital current to increase the noise of the analog circuit. Basically, it is right to divide the modulus / division. It should be noted that the signal trace as far as possible not across the division of the place, and do not let the power supply and the signal return current path changes too much. The number of digital signal lines can not cross the request because the speed of the digital signal is slightly faster to return the current path will be as far as possible below the bottom of the line to return to the source of digital signals, if the number of signal lines cross, the return current The resulting noise will appear in the analog circuit area.

The analog circuit uses star ground. The current consumption of audio power amplifiers is generally large, which may adversely affect their own ground or other reference ground.

The unused area on the circuit board into a ground plane. Grounding is achieved near the signal trace to divert excess high frequency energy from the signal line to the earth by capacitive coupling.