WM8711SEDSSLASHR datasheet(18/47 Pages) WOLFSON

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Production Data

WM8711 / WM8711L

PD Rev 4.3 September 2006

DAC

The WM8711/L employs a multi-bit sigma delta oversampling digital to analogue converter. The

scheme for the converter is illustrated in Figure 7.

FROM DAC

DIGITAL

FILTERS

TO LINE OUTPUT

Figure 7 Multi-Bit Oversampling Sigma Delta Schematic

The DAC converts the multi-level digital audio data stream from the DAC digital filters into high quality

analogue audio.

LINE OUTPUTS

The WM8711/L provides two low impedance line outputs LLINEOUT and RLINEOUT, suitable for

driving typical line loads of impedance 10K and capacitance 50pF.

The LLINEOUT and RLINEOUT outputs are only available at a line output level and are not level

adjustable in the analogue domain, having a fixed gain of 0dB. The level is fixed such that at the DAC

full scale level the output level is Vrms at AVDD = 3.3 volts. Note that the DAC full scale level tracks

directly with AVDD. The scheme is shown in Figure 8. The line output includes a low order audio low

pass filter for removing out-of band components from the sigma-delta DAC. Therefore no further

external filtering is required in most applications.

VMID

FROM LINE

INPUTS

LINEOUT

FROM DAC

BYPASS

TO HEADPHONE AMP

DACSEL

Figure 8 Line Output Schematic

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

the BYPASS path. 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.

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