wm8750 Wolfson Microelectronics plc, wm8750 Datasheet - Page 20

• Manufacturer Part Number: wm8750
• Description: Stereo Codec For Portable Audio Applications
• Manufacturer: Wolfson Microelectronics plc

WM8750L
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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.
Table 6 Mono Mixing
Table 7 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).
Table 8 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.
Figure 8 Microphone Bias Schematic
R31 (1Fh)
ADC input
Mode
R23 (17h)
Additional
Control (1)
R25 (19h)
Power
Management (1)
REGISTER
REGISTER
ADDRESS
ADDRESS
REGISTER
VMID
ADDRESS
BIT
7:6
BIT
3:2
1
BIT
MONOMIX
[1:0]
DATSEL
[1:0]
LABEL
internal
resistor
internal
resistor
LABEL
MICB
LABEL DEFAULT
AGND
DEFAULT
DEFAULT
MICB
00
00
0
MICBIAS
= 1.8 x VMID
= 0.9 X AVDD
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
Microphone Bias Enable
0 = OFF (high impedance output)
1 = ON
00: Stereo
01: Analogue Mono Mix (using left ADC)
10: Analogue Mono Mix (using right ADC)
11: Digital Mono Mix
DESCRIPTION
DESCRIPTION
DESCRIPTION
PD Rev 4.3 October 2006
Production Data
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