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WM8521
The WM8521 is hardware programmable providing the user with options to select input audio data
format, de-emphasis and mute.
HARDWARE CONTROL MODES
MUTE AND AUTO MUTE OPERATION
Pin 5 (MUTE) controls the mute function, or can be used as an output to monitor the state of
the automuted signal.
MUTE PIN
0
1
Floating
Normal Operation, MUTE off
Mute DAC channels
Enable IZD, MUTE becomes an output to indicate when IZD occurs.
DESCRIPTION
Table 2 Mute and Automute Control
1.5
1
0.5
0
-0.5
-1
-1.5
-2
-2.5
0
0.001
0.002
0.003
Time(s)
0.004
0.005
0.006
Figure 7 Application and Release of 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. Refer to Figure 7.
Therefore if MUTE is tied low then mute is disabled and the automute function is overridden.
If MUTE is floating or connected to a high impedance then the automute function will operate. The
AUTOMUTED internal signal, which is generated by the IZD function, is connected to the MUTE pin
internally via a 10k resistor. This can provide a weak output (10k source impedance) which can be
used to drive external mute circuits. Refer to Figure 8.
The Infinite Zero Detect (IZD) function detects 1024 zero value audio samples applied to both
channels. After such an event, a latch is set whose output is the AUTOMUTED internal signal.
AUTOMUTED will be reset as soon as either channel receives a non-zero input.
w
PP Rev 1.3 December 2004
13
WOLFSON [ WOLFSON MICROELECTRONICS PLC ]
