WM8750L datasheet(18/56 Pages) WOLFSON

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WM8750L

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PP Rev 1.77 May 2003

MONO MIXING

The stereo ADC can operate as a stereo or mono device, or the two channels can be mixed to mono,

either in the analogue domain (i.e. before the ADC) or in the digital domain (after the ADC).

MONOMIX selects the mode of operation. For analogue mono mix either the left or right channel

ADC can be used, allowing the unused ADC to be powered off or used for a dc measurement

conversion. The user also has the flexibility to select the data output from the audio interface using

DATSEL. The default is for left and right channel ADC data to be output, but the interface may also

be configured so that e.g. left channel ADC data is output as both left and right data for when an

analogue mono mix is selected.

Note:

If DC measurement is selected this overrides the MONOMIX selection.

ADDRESS

BIT

LABEL

DEFAULT

DESCRIPTION

R31 (1Fh)

ADC input

Mode

7:6

MONOMIX

[1:0]

00: Stereo

01: Analogue Mono Mix (using left ADC)

10: Analogue Mono Mix (using right ADC)

11: Digital Mono Mix

Table 5 Mono Mixing

ADDRESS

BIT

LABEL

DEFAULT

DESCRIPTION

R23 (17h)

Additional

Control (1)

3:2

DATSEL

[1:0]

00: left data=left ADC; right data =right ADC

01: left data =left ADC; right data = left ADC

10: left data = right ADC; right data =right

ADC

11: left data = right ADC; right data = left

ADC

Table 6 ADC Data Output Configuration

The MICBIAS output provides a low noise reference voltage suitable for biasing electret type

microphones and the associated external resistor biasing network. Refer to the Applications

Information section for recommended external components. The output can be enabled or disables

using the MICB control bit (see also the “Power Management” section).

ADDRESS

BIT

LABEL

DEFAULT

DESCRIPTION

R25 (19h)

Power

Management (1)

MICB

Microphone Bias Enable

0 = OFF (high impedance output)

1 = ON

Table 7 Microphone Bias Control

The internal MICBIAS circuitry is shown below. Note that the is a maximum source current capability

for MICBIAS is 3mA. The external biasing resistors therefore must be large enough to limit the

MICBIAS current to 3mA.

AGND

MICBIAS

= 1.8 x VMID

= 0.9 X AVDD

VMID

internal

resistor

internal

resistor

MICB

Figure 6 Microphone Bias Schematic

PGA CONTROL

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