Audio layout?

Talk about your layout experiences for the audio line on phone design. i know it's more important than RF layout.

The only think that I can say is, you will never fail an FTA if you have a bad audio layout, but you have a lot of chances to fail if your RF layout sucks.

Though audio circuit looks trivial, but it could determine the final speech quality of your phone.

To combat the TDD burst noise of the RF transmission, make sure you place some cap (33pf) across the MIC input (directly at the MIC pads).

To reduce echo, pay attention to the speaker placement.

need to take care about grounding issues, very important in audio

in two way case,the track will affect the wave phase.So must using equal line to confirm the phase.

When you do layout, you are basically connecting the elements of your circuit. There are a number of basic layout rules that should be followed in every layout (grounding issues, for example, are always important). The layout problems are always related to the non-ideal effects of such connections (parasitic resistances, capacitances and inductances).

When you are working with low frequencies (audio) reactance of parasitic capacitors and inductors can usually be (almost) ignored and you only have to care with the parasitic resistors. For example, in the output stage of an audio power amplifier you should have large PCB traces, to minimize parasitic resistances and avoid significant IR drops that occur, due to the large currents that can flow there.

As you go up in frequency the other parasitic elements start becoming important and the situation becomes much more complicated. So, it is NOT true that RF layout is less critical that audio layout. If you work at sufficiently high frequencies, your metal connection can stop behaving like connection (you have a transmission line, in which a number of complex effects can occur, if you are not careful).

If you are interested in the issues related with audio (layout and much more), you should look at the book named ?Audio Power Amplifier Handbook? from Douglas Self.