WM8976_11 Datasheet, PDF (27/114 Pages) Wolfson Microelectronics plc – Stereo CODEC with Speaker Driver

Production Data
WM8976
REGISTER BIT
LABEL
ADDRESS
R47
2:0 AUXL2BOOSTVOL
Input BOOST
control
6:4 L2_2BOOSTVOL
Table 8 Input BOOST Stage Control
DEFAULT
DESCRIPTION
000
Controls the auxiliary amplifier 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
000
Controls the L2 pin 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
The BOOST stage is enabled under control of the BOOSTEN register bit.
REGISTER
ADDRESS
R2
Power
management
2
BIT
LABEL
4
BOOSTENL
DEFAULT
DESCRIPTION
0
Input BOOST enable
0 = Boost stage OFF
1 = Boost stage ON
Table 9 Input BOOST Enable Control
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. When MBVSEL=0, MICBIAS=0.9*AVDD and when MBVSEL=1,
MICBIAS=0.65*AVDD. The output can be enabled or disabled using the MICBEN control bit.
REGISTER
ADDRESS
R1
Power
management 1
BIT LABEL DEFAULT
4
MICBEN 0
Table 10 Microphone Bias Enable Control
DESCRIPTION
Microphone Bias Enable
0 = OFF (high impedance output)
1 = ON
REGISTER
ADDRESS
R44
Input control
BIT LABEL
8
MBVSEL
DEFAULT
0
Table 11 Microphone Bias Voltage Control
DESCRIPTION
Microphone Bias Voltage Control
0 = 0.9 * AVDD
1 = 0.65 * AVDD
The internal MICBIAS circuitry is shown in Figure 16. 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.
w
PD, Rev 4.5, November 2011
27