Production Data

WM8768

w

PD Rev 4.1 March 2005

27

AUTOMUTE

The WM8768 can automute by counting zero samples on the DIN1/2/3/4 inputs. When 1024 zero

samples are counted on one channel, one of four internal zero flags (zflag1/2/3/4 shown in figure 2)

is raised. Depending on the external hardware and settings of DZFM, MPD and IZD, different

automute operations are possible.

MUTE PIN AS OUTPUT

If the MUTE pin is connected to a high impedance (input to external mute circuitry for example) or left

floating, zflag1/2/3/4 will be output on the Mute pin dependent on DZFM settings. This is described in

Table 12 below. The output impedance of the MUTE pin is 10kOhms

{DZFM4,DZFM

[1:0]}

CONDITION UNDER WHICH MUTE

PIN DRIVEN HIGH

000

Zflag1, 2, 3 and 4 all high

001

Zflag1 high

010

Zflag2 high

011

Zflag3 high

100

Zflag4 high

101

Zflag1 and 2 high

110

Zflag1, 2 and 3 high

111

Zflag3 and 4 high

Table 12 Effect of DZFM on Mute Pin Output

When the Mute pin is used as an output, its logic level remains connected to the DZFM selector

inside the chip (see figure 1). So, when the WM8768 drives the Mute pin high, the output DACs will

also softmute as described by Table 13.

MPD

{DZFM4,DZFM [1:0]}

CHANNELS MUTED WHEN

MUTE PIN DRIVEN HIGH

0

000

All Channels

0

001

CH1

0

010

CH2

0

011

CH3

0

100

CH4

0

101

CH1 and CH2

0

110

CH1, CH2 and CH3

0

111

CH3 and CH4

1

000

All Channels

1

001

All Channels

1

010

All Channels

1

011

All Channels

1

100

All Channels

1

101

All Channels

1

110

All Channels

1

111

All Channels

Table 13 Mute Pin Decode when Mute Pin as Output