Normal Mode; Limiter Mode - Cirrus Logic WM8940 Manual

32

NORMAL MODE

In normal mode, the ALC will attempt to maintain a constant signal level by increasing or decreasing
the gain of the PGA. The following diagram shows an example of this.
Input
Signal
ALCSEL
PGA
Gain
V
step
Output
of PGA
Figure 12 ALC Normal Mode Operation

LIMITER MODE

In limiter mode, the ALC will reduce peaks that go above the threshold level, but will not increase the
PGA gain beyond the starting level. The starting level is the PGA gain setting when the ALC is
enabled in limiter mode. If the ALC is started in limiter mode, this is the gain setting of the PGA at
start-up. If the ALC is switched into limiter mode after running in ALC mode, the starting gain will be
the gain at switchover. The diagram below shows an example of limiter mode.
t
t
ATK
DCY
WM8940
ALCLVL
Rev 4.4