Sorry for the late reply.
I understand that the application note states that whether the noise threshold can be clearly distinguished from the input signal determines the maximum gain applied by the ALC.
In this measurement example, the noise threshold is -90dBFS (default value) and the analog input level is -62dBV, so when the PGA is 0dB, the digital input level is -68dBFS.
There is a difference of more than 20dB between the noise threshold and the digital input level, does that mean that the maximum ALC gain may not apply?
If there is a case where it is not applied, why is the ALC applied gain when PGA=0dB larger than when PGA=6dB? I don't understand this part.
PGA=0dB … Output Level=-26dBFS
PGA=6dB …Output Level=-43dBFS
PGA=12dB … Output Level=-43dBFS
PGA=18dB …Output Level=-43dBFS
PGA=24dB …Output Level=-43dBFS
PGA=30dB … Output Level=-38dBFS
PGA=36dB … Output Level=-32dBFS
PGA = 42dB … Output Level = -26dBFS
