WM8772 datasheet(49/73 Pages) WOLFSON

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WM8772EFT – 32 LEAD TQFP

PD Rev 4.2 October 2005

The signal processing for the WM8772EFT typically operates at an oversampling rate of 128fs for

both ADC and DAC. The exception to this for the DAC is for operation with a 128/192fs system clock,

e.g. for 192kHz operation, when the oversampling rate is 64fs. For ADC operation at 96kHz it is

recommended that the user set the ADCOSR bit. This changes the ADC signal processing

oversample rate to 64fs.

System Clock Frequency (MHz)

SAMPLING

RATE

(DACLRC/

ADCLRC)

128fs

192fs

256fs

384fs

512fs

768fs

32kHz

4.096

6.144

8.192

12.288

16.384

24.576

44.1kHz

5.6448

8.467

11.2896

16.9340

22.5792

33.8688

48kHz

6.144

9.216

12.288

18.432

24.576

36.864

96kHz

12.288

18.432

24.576

36.864

Unavailable Unavailable

192kHz

24.576

36.864

Unavailable Unavailable Unavailable Unavailable

Table 17 System Clock Frequencies Versus Sampling Rate

(ADC does not support 128fs and 192fs)

HARDWARE CONTROL MODES

When the MODE pin is held high, the following hardware modes of operation are available.

Note: When in hardware mode the ADC and DAC will only run in slave mode.

MUTE AND AUTOMUTE OPERATION

In both hardware and software modes, MUTE controls the selection of MUTE directly, and can be

used to enable and disable the automute function. This pin becomes an output when left floating and

indicates infinite ZERO detect (IZD) has been detected.

DESCRIPTION

Normal Operation

Mute DAC channels

Floating

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

L=IZD detected, H=IZD not detected.

Table 18 Mute and Automute Control

Figure 43 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

decay exponentially from the DC level of the last input sample. The output will decay towards VMID

with a time constant of approximately 64 input samples. If MUTE is applied to all channels for 1024

or more input samples the outputs will be connected directly to VMID if IZD is set. When MUTE is de-

asserted, the output will restart immediately from the current input sample.

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