WM8728
Production Data
HARDWARE CONTROL MODES
When the MODE pin is held low, the following hardware modes of operation are available.
MUTE AND AUTOMUTE OPERATION
In both hardware and software modes, pin 17 (MUTEB) controls the selection of MUTE directly,
and can be used to enable and disable the automute function. Automute is enabled by leaving
MUTEB pin floating, it is disabled by applying a signal to the pin. When left floating this pin
becomes an output and indicates infinite ZERO detect (IZD), see also pin 5 (ZERO). The status
of IZD controls the selection of MUTE when automute is enabled. When IZD is detected MUTE is
enabled and when IZD is not detected MUTE is disabled.
MUTEB PIN
DESCRIPTION
0
1
Mute DAC channels
Normal Operation
Floating
MUTEB becomes an output to indicate when IZD occurs.
L=IZD detected (MUTE enabled), H=IZD not detected (MUTE disabled).
Table 2 Mute and Automute Control
ZERO PIN
DESCRIPTION
0
1
Indicates Infinite Zero detected from the digital input.
Indicates Infinite Zero not detected from the digital input.
Table 3 Zero Pin Output
Figure 15 shows the application and release of MUTE whilst a full amplitude sinusoid is being
played at 48kHz sampling rate. When MUTE (lower trace) is asserted, the output (upper trace)
begins to decay exponentially from the DC level of the last input sample. The output will decay
towards VMID with a time constant of approximately 64 input samples. When MUTE is de-
asserted, the output will restart almost immediately from the current input sample.
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 15 Application and Release of Soft Mute
The MUTEB pin is an input to select mute or not mute. MUTEB is active low; taking the pin low
causes the filters to soft mute, ramping down the audio signal over a few milliseconds. Taking
MUTEB high again allows data into the filter.
PD, Rev 4.6, August 2008
18
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WOLFSON [ WOLFSON MICROELECTRONICS PLC ]
