WM8731 datasheet(25/56 Pages) WOLFSON

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WM8731

Advanced Information

WOLFSON MICROELECTRONICS LTD

AI Rev 2.0 February 2001

VMID

FROM LINE

INPUTS

LINEOUT

FROM DAC

BYPASS

TO HEADPHONE AMP

DACSEL

FROM MICROPHONE

INPUT

SIDETONE

Figure 18 Line Output Schematic

The DAC output, Line Input and microphone are summed into the Line Output. In DAC mode only the

output from the DAC is routed to the line outputs. In Bypass mode the Line Input is summed into the

Line Outputs. In Side Tone mode the Microphone Input is summed into the Line Output. These

features can be used for either over-dubbing or, if the DAC is muted, as a pure analogue bypass or

Side Tone feature, so avoiding any digital signal processing.

The line output is muted by either muting the DAC (analogue) or Soft Muting (digital) and disabling

the BYPASS and SIDETONE paths. Refer to the DAC section for more details. Whenever the DAC

is muted or the device placed into standby mode the DC voltage is maintained at the line outputs to

prevent any audible clicks from being present.

The software control for the line outputs is shown in Table 7.

ADDRESS

BIT

LABEL

DEFAULT

DESCRIPTION

BYPASS

Bypass Switch

1 = Enable Bypass

0 = Disable Bypass

DACSEL

DAC Select

1 = Select DAC

0 = Don’t select DAC

0000100

Analogue

Audio Path

Control

5SIDETONE

Side Tone Switch

1 = Enable SideTone

0 = Disable Side Tone

Table 7 Output Software Control

The recommended external components are shown in Figure 19.

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