WM8976 Wolfson Microelectronics Ltd., WM8976 Datasheet - Page 24

• Manufacturer Part Number: WM8976
• Description: The WM8976 is a low power, high quality stereo codec designed for portable applications such as Digital still camera or Digital Camcorde
• Manufacturer: Wolfson Microelectronics Ltd.

WM8976
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Table 7 Input BOOST Stage Control
Table 8 Input BOOST Enable Control
MICROPHONE BIASING CIRCUIT
Table 9 Microphone Bias Enable Control
Table 10 Microphone Bias Voltage Control
The BOOST stage is enabled under control of the BOOSTEN register bit.
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=0.65*AVDD. The output can be enabled or disabled using the MICBEN control bit.
The internal MICBIAS circuitry is shown in Figure 9.
capability for MICBIAS is 3mA. The external biasing resistors therefore must be large enough to limit
the MICBIAS current to 3mA.
R47
Input BOOST
control
R2
Power
management
2
R1
Power
management 1
R44
Input control
REGISTER
REGISTER
REGISTER
ADDRESS
ADDRESS
ADDRESS
REGISTER
ADDRESS
2:0
6:4
4
8
BIT
BIT
BIT
4
BIT
AUXL2BOOSTVOL
L2_2BOOSTVOL
BOOSTENL
MBVSEL
LABEL
LABEL
MICBEN
When MBVSEL=0, MICBIAS=0.9*AVDD and when MBVSEL=1,
LABEL
LABEL
0
DEFAULT
0
DEFAULT
0
DEFAULT
000
000
DEFAULT
Microphone Bias Voltage Control
0 = 0.9 * AVDD
1 = 0.65 * AVDD
Microphone Bias Enable
0 = OFF (high impedance output)
1 = ON
Note that the maximum source current
Input BOOST enable
0 = Boost stage OFF
1 = Boost stage ON
Controls the auxilliary amplifer to
the input boost stage:
000=Path disabled (disconnected)
001=-12dB gain through boost
stage
010=-9dB gain through boost
stage
…
111=+6dB gain through boost
stage
boost stage:
000=Path disabled (disconnected)
001=-12dB gain through boost
stage
010=-9dB gain through boost
stage
…
111=+6dB gain through boost
stage
Controls the L2 pin to the input
DESCRIPTION
DESCRIPTION
DESCRIPTION
DESCRIPTION
PP Rev 3.0 April 2006
Pre-Production
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