WM8753 Wolfson Microelectronics plc, WM8753 Datasheet - Page 26

• Manufacturer Part Number: WM8753
• Description: HI FI AND TELEPHONY DUAL CODEC
• Manufacturer: Wolfson Microelectronics plc

Advanced Information
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Table 12 MIC Select Control
Table 13 Microphone Bias Control
Table 14 Microphone Bias Voltage Control
It is possible to connect up to three microphones single endedly.
MIC1 input , microphone2 to the MIC2 input, microphone3 to the MIC2N input and MIC1N is
connected to Vref. The gains, MIC1BOOST and MIC2BOOST, should be set to be identical and
micamp2 must be disabled. Any of the three microphones can then be selected as the output from
micamp1 using MICSEL.
MICROPHONE BIASING CIRCUIT
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 MICBIAS voltage can be altered via
the MBVSEL register bit.
MICBIAS=0.75*AVDD. The output can be enabled or disabled using the MICB control bit (see also
the “Power Management” section).
The internal MICBIAS circuitry is shown in Figure 8. Note that the maximum source current capability
for MICBIAS is 3mA. The external biasing resistors therefore must be large enough to limit the
MICBIAS current to 3mA.
Table 11 ADC Polarity Control
SINGLE ENDED OPERATION
R2 (02h)
ADC control
R51 (33h)
Mic Select
R20 (14h)
Power
Management (1)
R51 (33h)
Mic bias comp
control
REGISTER
ADDRESS
REGISTER
REGISTER
ADDRESS
ADDRESS
REGISTER
ADDRESS
8
[7:6]
BIT
[6:5]
BIT
BIT
5
BIT
MBVSEL
ADCPOL[1:0]
MICSEL[1:0]
LABEL
MICB
When MBVSEL=0, MICBIAS=0.9*AVDD and when MBVSEL=1,
LABEL
LABEL
LABEL
0
DEFAULT
0
DEFAULT
00
00
DEFAULT
DEFAULT
Microphone Bias Voltage Control
0 = 0.9 * AVDD
1 = 0.75 * AVDD
Microphone Bias Enable
0 = OFF (high impedance output)
1 = ON
00 = Polarity not inverted
01 = L polarity invert
10 = R polarity invert
11 = L and R polarity invert
Microphone selected
00 : MIC1
01 : MIC2
10 : MIC3
11 : unused
Microphone1 is connected to the
DESCRIPTION
DESCRIPTION
DESCRIPTION
DESCRIPTION
AI Rev 3.1 June 2004
WM8753L
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