WM8980_07 datasheet(34/112 Pages) WOLFSON

34 / 112 page

WM8980

Pre-Production

PP Rev 3.1 March 2007

The BOOST stage is enabled under control of the BOOSTEN register bit.

ADDRESS

BIT

LABEL

DEFAULT

DESCRIPTION

BOOSTENL

Left channel Input BOOST enable

0 = Boost stage OFF

1 = Boost stage ON

Power

management

BOOSTENR

Right channel Input BOOST enable

0 = Boost stage OFF

1 = Boost stage ON

Table 11 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.

ADDRESS

BIT

LABEL

DEFAULT

DESCRIPTION

Power

management 1

MICBEN

Microphone Bias Enable

0 = OFF (high impedance output)

1 = ON

Table 12 Microphone Bias Enable Control

ADDRESS

BIT

LABEL

DEFAULT

DESCRIPTION

R44

Input control

MBVSEL

Microphone Bias Voltage Control

0 = 0.9 * AVDD

1 = 0.65 * AVDD

Table 13 Microphone Bias Voltage Control

The internal MICBIAS circuitry is shown in Figure 17. 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.

Figure 17 Microphone Bias Schematic

WM8980 Datasheet(PDF) 34 Page - Wolfson Microelectronics plc

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