WM8728

Production Data

w

PD Rev 4.2 April 2004

16

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

Mute DAC channels

1

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

Indicates Infinite Zero detected from the digital input.

1

Indicates Infinite Zero not detected from the digital input.

Table 3 Zero Pin Output

Figure 11 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

asserted, the output will restart almost immediately from the current input sample.

-2.5

-2

-1.5

-1

-0.5

0

0.5

1

1.5

0

0.001

0.002

0.003

0.004

0.005

0.006

Time(s)

Figure 11 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.