Generally, the output of the previous sound source also has a bias voltage. If it is not handled properly, or the software timing is wrong after the system is turned on, it will also cause pop sound. At this time, it can be judged by turning on the power amplifier after en has been turned up. If EN has been turned up and there is pop sound, it is judged as the above situation. Grab the sound source and start-up sequence with an oscilloscope. It is suggested that after the previous chip outputs stably (the bias voltage is established stably), MCU will give en start-up signal.

    For example, when the prompt tone is played during shutdown, if the software immediately pulls down en and turns off the sound source at the same time, as shown in the following figure, because the general power amplifier will do a little shutdown delay, the main chip MCU will turn off the sound source when the power amplifier is not completely turned off, and the inconsistent discharge rate will cause the differential pressure to be amplified by the power amplifier, resulting in the shutdown pop tone.