Production Data
WM8976
w
PD, Rev 4.5, November 2011
35
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.
Figure 19 ALC Limiter Mode Operation
ALC LIMITER MODE INITIALISATION SEQUENCE
In order to properly initialise the ALC function, the following sequence of register writes is required:
1.
Set INPPGAVOLL to the required input PGA gain (R45[5:0]).
2.
Enable analogue inputs (R44[2:0]) as required.
3.
Disable INPPGAENL (R2[2] =0).
4. Set ALCMAXGAIN (R32[5:3]) and ALCMINGAIN (R32[2:0]) to the required level for
operation.
5.
Set ALCLVL (R33[3:0]) to the required level for operation.
6.
Set R34 to 0x000.
7.
Wait for 1ms to allow the input PGA gain to update by the limiter circuit.
8.
Enable Limiter mode (R34[8]=1).
9.
Wait for 1ms to allow the input PGA gain to update by the limiter circuit.
10. Enable INPPGAENL (R2[2] =1).
Содержание WM8976
Страница 13: ...Production Data WM8976 w PD Rev 4 5 November 2011 13 AUDIO PATHS OVERVIEW Figure 1 WM8976 Audio Signal Paths...
Страница 40: ...WM8976 Production Data w PD Rev 4 5 November 2011 40 Figure 21 ALCLVL...
Страница 43: ...Production Data WM8976 w PD Rev 4 5 November 2011 43 Figure 23 ALC Operation Above Noise Gate Threshold...
Страница 52: ...WM8976 Production Data w PD Rev 4 5 November 2011 52 Figure 27 Left Right Output Channel Mixers...
