WM8746

Production Data

w

March 2006, PD Rev 4.0

16

MUTE MODES

Setting the MUTE register bit will apply a 'soft' mute to the input of the digital filters:

REGISTER ADDRESS

BIT

LABEL

DEFAULT

DESCRIPTION

0000010

DAC Channel Control

0

MUTE

0

Soft Mute select

0 : Normal Operation

1: Soft mute all channels

Figure 10 Application and Release of Soft Mute

Figure 10 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

with a time constant of approximately 64 input samples. If MUTE is applied for 1024 or more input

(infinite zero detect) bit. When MUTE is de-asserted, the output will restart almost immediately from

the current input sample.

Note that all other means of muting the DAC channels: setting the PL[3:0] bits to 0, setting the

PWDN bit or setting attenuation to 0 will cause much more abrupt muting of the output.

Setting the IZD register bit will enable the infinite zero detect feature:

REGISTER ADDRESS

BIT

LABEL

DEFAULT

DESCRIPTION

0000010

DAC Channel Control

4

IZD

0

Internal Analogue Mute Disable

0 : Disable Analogue Mute

1: Enable Analogue Mute

With IZD=1, applying MUTE for 1024 consecutive input samples will cause all outputs to be

all 6 channels, and IZD=0. It will be removed as soon as any channel receives a non-zero input.

The MUTE pin can be used as an input. In this case it performs the same function as the MUTE

register bit. Driving the MUTE pin high will apply a 'soft' mute. Driving it low again, will remove the

MUTE immediately. Note that this hardware mute feature doesn't require the MODE pin to be set

high.

-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)