WM8761

Production Data

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PD Rev 4.0 May 2004

13

HARDWARE CONTROL MODES

The WM8761 is hardware programmable providing the user with options to select input audio data

format, de-emphasis and mute.

MUTE AND AUTO MUTE OPERATION

Pin 10 (MUTE) controls selection of MUTE directly, and can be used to enable and disable the

automute function, or as an output of the automuted signal.

MUTEB 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

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. Refer to Figure 7.

The Infinite Zero Detect (IZD) 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 connected through a 10kohm 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. 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 (10k source impedance) so can be used to drive

external mute circuits. AUTOMUTED will be removed as soon as any 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)