WM8985_07 WOLFSON [Wolfson Microelectronics plc], WM8985_07 Datasheet - Page 37

• Manufacturer Part Number: WM8985_07
• Description: Multimedia CODEC With Class D Headphone and Line Out
• Manufacturer: WOLFSON [Wolfson Microelectronics plc]

Pre-Production
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Table 9 Input BOOST Stage Control
Table 10 Input BOOST Enable Control
MICROPHONE BIASING CIRCUIT
Table 11 Microphone Bias Enable Control
Table 12 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*AVDD1. The output can be enabled or disabled using the MICBEN control bit.
The internal MICBIAS circuitry is shown in Figure 18.
capability for MICBIAS is 3mA. The external biasing resistors therefore must be large enough to limit
the MICBIAS current to 3mA.
R2 (02h)
Power
management
2
R1 (01h)
Power
management 1
R44 (2Ch)
Input control
REGISTER
REGISTER
REGISTER
ADDRESS
ADDRESS
ADDRESS
REGISTER
ADDRESS
6:4
4
5
8
BIT
BIT
BIT
4
BIT
R2_2BOOSTVOL
BOOSTENL
BOOSTENR
MBVSEL
LABEL
LABEL
When MBVSEL=0, MICBIAS=0.9*AVDD1 and when MBVSEL=1,
MICBEN
LABEL
LABEL
0
0
DEFAULT
DEFAULT
0
0
DEFAULT
000
DEFAULT
Microphone Bias Enable
0 = OFF (high impedance output)
1 = ON
Microphone Bias Voltage Control
0 = 0.9 * AVDD1
1 = 0.65 * AVDD1
Note that the maximum source current
Left channel Input BOOST enable
0 = Boost stage OFF
1 = Boost stage ON
Right channel Input BOOST enable
0 = Boost stage OFF
1 = Boost stage ON
Controls the R2 pin to the right
channel input boost stage:
000 = Path disabled
(disconnected)
001 = -12dB
010 = -9dB gain
011 = -6dB gain
100 = -3dB gain
101 = +0dB gain
110 = +3dB gain
111 = +6dB gain
DESCRIPTION
DESCRIPTION
DESCRIPTION
PP, Rev 3.5, January 2007
DESCRIPTION
WM8985
37