We are using the ALC function of the DA7212 with success in several projects.
Recently we tried to use the automatic DC offset calibration, accessible through
the ALC_CTRL_1 register.
However, when we have completed this procedure, following the recommended
sequence, the ALC will behave strangely:
- It will, as expected, lower the gain and thus the output volume when high sounds comes in
- It will NOT increase the gain again, unless there is SOME sound coming in.
If the input is quiet, the gain will stay low indefinetly.
We have tried in many ways to remedy this behaviour,
since it will NOT work in our application, but have not succeeded.
For example, playing around with the noise threshold, min and max gains, attack and sustain rates
seem to not affect this problem at all. IF we go to a fully digital ALC, then this problem
goes away, but we need to have analog + digital ALC
Does anyone have an explanation to why this is happening, and a proposed solution?