WM8772SEDSSLASHV datasheet(50/73 Pages) WOLFSON

50 / 73 page

WM8772EFT – 32 LEAD TQFP

Production Data

PD Rev 4.2 October 2005

Figure 43 Application and Release of Soft 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.

The automute 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 wire

OR’ed through a 10kΩ 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 unless the IZD register bit is set. 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 (10kΩ source impedance) and can be

used to drive external mute circuits. AUTOMUTED will be removed as soon as any channel receives

a non-ZERO input.

A diagram showing how the various Mute modes interact is shown below Figure 20.

IZD (Register Bit)

AUTOMUTED

(Internal Signal)

10k

Ω

MUTE (Register Bit)

SOFTMUTE

(Internal

Signal)

MUTE

Figure 44 Selection Logic for MUTE Modes

-2.5

-2

-1.5

-1

-0.5

0.5

1.5

0.001

0.002

0.003

0.004

0.005

0.006

Time(s)

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