WM8972LEFLSLASHR datasheet(14/49 Pages) WOLFSON

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WM8972L

Preliminary Technical Data

PTD Rev 2.2 June 2004

ADDRESS

BIT

LABEL

DEFAULT

DESCRIPTION

7:6

INSEL

Input Select

00 = INPUT1

01 = INPUT2

11 = L-R Differential (either INPUT1+

– INPUT1- or INPUT2+ –

INPUT2-, selected by DS)

R32 (20h)

ADC Signal

Path Control

5:4

MICBOOST

Microphone Gain Boost

00 = Boost off (bypassed)

01 = 13dB boost

10 = 20dB boost

11 = 29dB boost

Table 2 Input Software Control

ADDRESS

BIT

LABEL

DEFAULT

DESCRIPTION

R31 (1Fh)

ADC Input Mode

Differential input select

0: INPUT1+ – INPUT1-

1: INPUT2+ – INPUT2-

Table 3 Differential Input Select

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 output can be enabled or disabled

using the MICB control bit (see also the “Power Management” section).

ADDRESS

BIT

LABEL

DEFAULT

DESCRIPTION

R25 (19h)

Power

Management (1)

MICB

Microphone Bias Enable

0 = OFF (high impedance output)

1 = ON

Table 4 Microphone Bias Control

The internal MICBIAS circuitry is shown below. Note that the is a maximum source current capability

for MICBIAS is 3mA. The external biasing resistors therefore must be large enough to limit the

MICBIAS current to 3mA.

AGND

MICBIAS

= 1.8 x VMID

= 0.9 X AVDD

VMID

internal

resistor

internal

resistor

MICB

Figure 6 Microphone Bias Schematic

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