WM8774 datasheet(21/42 Pages) WOLFSON

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WM8774

PP Rev 1.0 June 2002

ADC OVERSAMPLING RATE SELECT

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.

BIT

LABEL

DEFAULT

DESCRIPTION

10111

ADC Oversampling Rate

ADCOSR

ADC oversampling rate select

0: 128x oversampling

1: 64x oversampling

MUTE MODES

Setting DMUTE will apply a ‘soft’ mute to the input of the DAC digital filters.

BIT

LABEL

DEFAULT

DESCRIPTION

10100

DAC Mute

DMUTE

DAC Soft Mute select

0 : Normal Operation

1: Soft mute enabled

Figure 17 Application and Release of Soft Mute

Figure 17 shows the application and release of DMUTE whilst a full amplitude sinusoid is being

played at 48kHz sampling rate. When DMUTE (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 DMUTE is applied for 1024

or more input samples, the DAC will be muted if IZD is set. When DMUTE is de-asserted, the output

will restart 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

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

-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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