Solutions for noise & pop sounds
    1. The speaker has a serious "squeak" broken sound, most of the reasons may be that the V(out) voltage is unstable, so it is best to measure the output voltage without load. It is also possible to measure VCC - the output/input voltage of boost. The normal VCC can be obtained from the customer's feedback resistance and VCC load resistance.
    2, the customer has noise: it is estimated that the signal interference, generally the interference factor of the power supply accounts for the largest proportion, it is recommended to measure the static current IQ.

    3. POP sound: This POP sound is ultimately caused by the DC level jump on the earphone channel when the codec starts working; There is no negative voltage on mobile phones or general handheld devices, and the sound source signal must be output at a DC level (such as 1/2VDD), so a DC jump from level 0 to 1/2VDD will inevitably produce a POP sound on the earphone after being capacitors. After all, it is still the sound of shelving capacitor charge and discha

    4, POP sound reduction method:

    Method 1: Generally speaking, the POP sound on the IC and when the power is off is caused by the instantaneous jump of the bias voltage. Therefore, to reduce the POP sound, it is necessary to suppress the transient of the IC's paranoid voltage Vbias. The method of Layout is to increase the filter capacitance of Vbias. For the TPA6132, the reference design is 1 uF, but the bias capacitor becomes too large, resulting in a longer build time for the IC, which makes people feel that the sound has not come out for a long time. In addition, excessive capacitance will also cause THD+N to deteriorate.
    Method 2: For TPA6132, by changing the timing, we turn off the class before the noise comes out, and modify the timing of Depop_mute# and Speaker_mute# through the software to make it turn off in advance.
    Method 3: Power on noise, ground plane rebound noise (such as some decoding chip beep pin ground, caused by the ground noise is not controlled by the pop sound), and so on, the first thing is to identify the source. Find another way. If you can't find it or can't solve it after finding it, you can try to string a resistor to suppress the amplitude of the pop sound, which of course also reduces the maximum volume of the headset.
    Method 4: There is another method: the pre-charging method, coupled with the pull-up and pull-down resistance to stabilize the DC voltage of the capacitor, which may have a better effect. Of course, first of all, we must confirm how high the DC bias 1/2VDD is (some can be set, some are fixed), so as to design the size of the pull-down resistance, so that the effect can be adjusted, and the pop noise can hardly be felt.
    Method 5: Some Codecs now have a register in the software that can set the rise time of this DC level, so that it jumps to 1/2VDD in a certain time, rather than a very steep rise edge, which can improve this POP sound to some extent. It also causes THD+N to deteriorate.
    5, the switching machine POP sound problem is currently the bottleneck problem of the entire audio amplifier, and the best solution is method two. For our Demo, for example, when switching songs, we can first hold EN to give him a low signal, and then let go when the music switch ends
   6, supplement: If the left and right channels are output in a fully differential way, it is not necessary to isolate the capacitor, but the headset can not use the standard four-wire headphone jack, this fully differential way, the headset is generally used with a dedicated output plug (shared with the debugging interface).
    7. Pay special attention to the common ground when DEMO, reduce the possibility of POP sound generation, and there will be standards when detecting.