WM8778SEDSSLASHR datasheet(26/50 Pages) WOLFSON

26 / 50 page

WM8778

Production Data

PD Rev 4.0 April 2005

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

R12 (0Ch)

0001100

ADC Oversampling Rate

ADCOSR

ADC Oversampling Rate Select

0: 128x oversampling

1: 64x oversampling

MUTE MODES

Setting MUTE for the DAC will apply a ‘soft’ mute to the input of the digital filters of the channel

muted.

BIT

LABEL

DEFAULT

DESCRIPTION

R8 (08h)

0001000

DAC Mute

DMUTE

DAC Soft Mute Select

0 : Normal Operation

1: Soft mute enabled

Figure 22 Application and Release of Soft Mute

Figure 22 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 to both

channels 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: 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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