Mobile phone circuit board design to improve audio performance should:
1. Carefully consider the underlying planning.
The ideal underlying planning should divide different types of circuits into different areas.
Use differential signals whenever possible.
Audio devices with differential input can suppress noise.In the middle of the difference signal is generally can not add ground line.For the application principle of difference signal, the most important point is to take advantage of the mutual coupling between difference signals, such as magnetic flux elimination, anti-noise ability, etc.Adding ground in the middle breaks the coupling effect.
There are two points to note about the wiring of the difference pair. One is that the lengths of the two lines should be as long as possible.There are two ways of parallelism, one is to walk two lines on the same side-by-side, and the other is to walk two lines on the upper and lower adjacent layers.Generally, there are many ways to implement the former side-by-side.
3. Isolate the ground current to avoid digital current increasing the noise of analog circuit.
Basically, it is right to separate module/number.It is important to note that the signal line should not cross the gap and that the backflow current path of the power supply and signal should not change too much.The requirement that the digital-analog signal's routing cannot be crossed is that the return current path of the faster digital signal will flow back to the source of the digital signal as far as possible along the ground near the bottom of the stripper. If the digital-analog signal is crossed, the noise generated by the return current will appear in the analog circuit area.
Analog circuit USES star ground.Audio power amplifiers generally consume a large amount of current, which may adversely affect their own grounding or other reference grounding.
Turn all unused areas of the circuit board into floor.Ground cover is implemented near the signal routing to shunt the excess high-frequency energy in the signal line to the ground through capacitive coupling.
Mobile phone circuit board design to improve audio performance should not:
Use hybrid circuits on the board.
Although the radiofrequency portion of a phone is generally considered analog, the noise from the radiofrequency portion coupled to the audio circuit is demodulated to audible noise.
5. Analog audio signal wiring is too long.
Too long analog audio traces may be subject to digital and rf noise.
Forget the importance of the ground loop.
Systems with poor grounding will have serious distortion, noise, crosstalk and low rf interference resistance.
7. Interrupt the natural circuit of digital current.
This path produces the smallest loop area, which can reduce the antenna effect and inductance effect.
8. It is neglected to place the by-pass capacitor as close as possible to the power supply pin of the by-pass capacitor.