This article introduces methods and strategies to improve the audio performance of mobile phone PCB design.
1. Carefully consider the underlying planning. The ideal layout should segregate different types of circuits into distinct areas.
2. Utilize differential signals whenever possible. Audio devices with differential inputs can effectively suppress noise. Adding a ground wire in the middle of a differential signal is generally not recommended, as the primary benefit of differential signals comes from the mutual coupling between them, which enhances magnetic flux elimination and noise immunity. Introducing a ground wire can disrupt this coupling effect. In the layout of differential pairs, two key aspects must be considered: the length of the two wires should be as long as feasible, and the distance between them (determined by differential impedance) must be kept constant and parallel. This parallelism can be achieved either by placing the wires side-by-side on the same layer or running them on two adjacent layers (over-under). Typically, side-by-side arrangements are more common.
3. Isolate the ground current to prevent digital current from increasing the noise in the analog circuit. It is essential to separate and isolate the analog and digital grounds. Signal traces should ideally avoid crossing these divisions, and the return current path for both power supply and signal should remain consistent. The reason digital-analog signal traces should not intersect is that the high-speed digital signal return current will flow back to its source along the ground near the trace’s bottom. If these traces cross, the return current may generate noise in the analog circuit area. Use star grounding for analog circuits, as audio power amplifiers typically draw substantial current, which could adversely affect grounding or other reference grounds. Convert all unused areas on the PCB into a ground plane to ensure grounding coverage near signal traces, allowing excess high-frequency energy to be shunted to ground via capacitive coupling.
Mobile phone PCB circuit board design to improve audio performance should not:
4. Use a hybrid circuit on the board. Although mobile phone RF areas are generally analog, noise from the RF section can couple into the audio circuit and become audible.
5. Have analog audio signal wiring that is excessively long. Long analog audio traces can pick up interference from digital and RF circuits.
6. Overlook the importance of ground loops. Poor grounding can lead to significant distortion, noise, crosstalk, and reduced RF immunity.
7. Disrupt the natural loop of digital current. Maintaining a minimal loop area reduces antenna influence and inductance effects.
8. Neglect placing the bypass capacitor as close as possible to the power supply pin being bypassed.
1. Carefully consider the underlying planning. The ideal layout should segregate different types of circuits into distinct areas.
2. Utilize differential signals whenever possible. Audio devices with differential inputs can effectively suppress noise. Adding a ground wire in the middle of a differential signal is generally not recommended, as the primary benefit of differential signals comes from the mutual coupling between them, which enhances magnetic flux elimination and noise immunity. Introducing a ground wire can disrupt this coupling effect. In the layout of differential pairs, two key aspects must be considered: the length of the two wires should be as long as feasible, and the distance between them (determined by differential impedance) must be kept constant and parallel. This parallelism can be achieved either by placing the wires side-by-side on the same layer or running them on two adjacent layers (over-under). Typically, side-by-side arrangements are more common.
3. Isolate the ground current to prevent digital current from increasing the noise in the analog circuit. It is essential to separate and isolate the analog and digital grounds. Signal traces should ideally avoid crossing these divisions, and the return current path for both power supply and signal should remain consistent. The reason digital-analog signal traces should not intersect is that the high-speed digital signal return current will flow back to its source along the ground near the trace’s bottom. If these traces cross, the return current may generate noise in the analog circuit area. Use star grounding for analog circuits, as audio power amplifiers typically draw substantial current, which could adversely affect grounding or other reference grounds. Convert all unused areas on the PCB into a ground plane to ensure grounding coverage near signal traces, allowing excess high-frequency energy to be shunted to ground via capacitive coupling.
Mobile phone PCB circuit board design to improve audio performance should not:
4. Use a hybrid circuit on the board. Although mobile phone RF areas are generally analog, noise from the RF section can couple into the audio circuit and become audible.
5. Have analog audio signal wiring that is excessively long. Long analog audio traces can pick up interference from digital and RF circuits.
6. Overlook the importance of ground loops. Poor grounding can lead to significant distortion, noise, crosstalk, and reduced RF immunity.
7. Disrupt the natural loop of digital current. Maintaining a minimal loop area reduces antenna influence and inductance effects.
8. Neglect placing the bypass capacitor as close as possible to the power supply pin being bypassed.
