WM8772EFT – 32 LEAD TQFP
Production Data
1.5
1
0.5
0
-0.5
-1
-1.5
-2
-2.5
0
0.001
0.002
0.003
0.004
0.005
0.006
Time(s)
Figure 43 Application and Release of Soft Mute
The MUTE pin is an input to select mute or not mute. MUTE is active high; taking the pin high causes
the filters to soft mute, ramping down the audio signal over a few milliseconds. Taking MUTE low
again allows data into the filter.
The automute function detects a series of ZERO value audio samples of 1024 samples long being
applied to both channels. After such an event, a latch is set whose output (AUTOMUTED) is wire
OR’ed through a 10kꢀ resistor to the MUTE pin. Thus if the MUTE pin is not being driven, the
automute function will assert mute.
If MUTE is tied low, AUTOMUTED is overridden and will not mute unless the IZD register bit is set. If
MUTE is driven from a bi-directional source, then both MUTE and automute functions are available. If
MUTE is not driven, AUTOMUTED appears as a weak output (10kꢀ source impedance) and can be
used to drive external mute circuits. AUTOMUTED will be removed as soon as any channel receives
a non-ZERO input.
A diagram showing how the various Mute modes interact is shown below Figure 20.
IZD (Register Bit)
AUTOMUTED
(Internal Signal)
10k
Ω
SOFTMUTE
(Internal
Signal)
MUTE
PIN
MUTE (Register Bit)
Figure 44 Selection Logic for MUTE Modes
PD Rev 4.2 October 2005
50
w
WOLFSON [ WOLFSON MICROELECTRONICS PLC ]
