WM8976 View Datasheet(PDF) - Wolfson Microelectronics plc

Part Name

Description

Manufacturer

WM8976

Stereo CODEC With Speaker Driver

Wolfson Microelectronics plc 

Pre-Production

VMID

WM8976

MBVSEL=0

MB

MICBIAS

= 1.8 x VMID

= 0.9 x AVDD

internal

resistor

MBVSEL=1

MICBIAS

= 1.3 x VMID

internal

= 0.65 x AVDD

resistor

AGND

Figure 9 Microphone Bias Schematic

ANALOGUE TO DIGITAL CONVERTER (ADC)

The WM8976 uses a multi-bit, oversampled sigma-delta ADC. The use of multi-bit feedback and

high oversampling rates reduces the effects of jitter and high frequency noise. The ADC Full Scale

input level is proportional to AVDD. With a 3.3V supply voltage, the full scale level is 1.0Vrms. Any

voltage greater than full scale may overload the ADC and cause distortion.

ADC DIGITAL FILTERS

The ADC filters perform true 24 bit signal processing to convert the raw multi-bit oversampled data

from the ADC to the correct sampling frequency to be output on the digital audio interface. The

digital filter path for each ADC channel is illustrated in Figure 10.

Figure 10 ADC Digital Filter Path

The ADC is enabled by the ADCENL/R register bit.

REGISTER

ADDRESS

R2

Power

management 2

BIT LABEL

0

ADCENL

Table 11 ADC Enable Control

DEFAULT

0

DESCRIPTION

Enable ADC:

0 = ADC disabled

1 = ADC enabled

w

PP Rev 3.0 April 2006

25

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