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WM8521

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PP Rev 1.3 December 2004

13

HARDWARE CONTROL MODES

The WM8521 is hardware programmable providing the user with options to select input audio data

format, de-emphasis and mute.

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

DESCRIPTION

0

Normal Operation, MUTE off

1

Mute DAC channels

Floating

Enable IZD, MUTE becomes an output to indicate when IZD occurs.

Table 2 Mute and Automute Control

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.

-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)