WM8729 데이터 시트보기 (PDF) - Wolfson Microelectronics plc

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WM8729

24-bit, 192kHz Stereo DAC

Wolfson Microelectronics plc 

WM8729

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HARDWARE CONTROL MODES

The WM8729 is hardware programmable providing the user with options to select input audio data

format, de-emphasis and mute.

MUTE AND AUTOMUTE OPERATION

Pin 14 (MUTEB) 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

Mute DAC channels

1

Normal Operation

Floating

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

Table 2 Mute and Automute Control

1.5

1

0.5

0

-0.5

-1

-1.5

-2

-2.5

0

0.001

0.002

0.003

Time(s)

0.004

0.005

0.006

Figure 5 Application and Release of MUTEB

The MUTEB pin is an input to select mute or not mute. MUTEB is active low; taking the pin low

causes the filters to soft mute, ramping down the audio signal over a few milliseconds. Taking

MUTEB high again allows data into the filter. Refer to Figure 5.

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 MUTEB pin. Thus if the MUTEB

pin is not being driven, the automute function will assert mute.

If MUTEB is tied high, AUTOMUTED is overridden and will not mute. If MUTEB is driven from a

bi-directional source, then both MUTE and automute functions are available. If MUTEB 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.

A diagram showing how the various Mute modes interact is shown below in Figure 6.

WOLFSON MICROELECTRONICS LTD

PP Rev 1.2 April 2001

9

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