Improve the performance of mobile phone circuit board design audio performance
Mobile phone circuit board design to improve the audio performance should be:
1. Consider the underlying plan carefully.
The ideal underlying plan should divide the different types of circuits into different areas.
2. 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 spacing 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 walking 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.
3. Isolate the ground current to avoid 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 and signal return current path changes too much. The number of signal-to-signal signal traces can not be crossed because the speed of the digital signal is slightly faster, and the return current path will try to return to the source of the digital signal along the ground near the bottom of the trace. If the digital signal is crossed, 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 have an adverse effect on their own ground or other reference ground.
The unused area on the circuit board into a ground plane. Grounding coverage is achieved near the signal trace to divert excess high frequency energy from the signal line to the earth by capacitive coupling.
Mobile phone circuit board design to improve audio performance should not:
4. Use a hybrid circuit on the board.
Although the radio frequency zone of the mobile phone is generally considered to be analog, the noise from the RF band coupled to the audio circuit is demodulated to be audible.
5. Analog audio signal wiring is too long.
Too long analog audio stitches may be subject to noise from digital and RF circuits.
6. forget the importance of grounding loops.
Poor grounding system will be serious distortion, noise, crosstalk and RF immunity and other issues.
7. Disconnect the digital circuit from the natural current.
This path produces a minimum loop area that reduces antenna and inductance effects.
8. Ignore the location where the bypass capacitor is to be placed close to the power supply pin that may be bypassed.