wm8974gefl-v Wolfson Microelectronics plc, wm8974gefl-v Datasheet - Page 19

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wm8974gefl-v

Manufacturer Part Number
wm8974gefl-v
Description
Mono Codec With Speaker Driver
Manufacturer
Wolfson Microelectronics plc
Datasheet
Production Data
w
ANALOGUE TO DIGITAL CONVERTER (ADC)
Figure 10 ADC Digital Filter Path
ADC DIGITAL FILTERS
Table 8 ADC Enable
The WM8974 uses a multi-bit, oversampled sigma-delta ADC channel. 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 1.0V
Any voltage greater than full scale may overload the ADC and cause distortion.
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 is illustrated in .
The ADC is enabled by the ADCEN register bit.
Figure 9 Microphone Bias Schematic
R2
Power management
2
REGISTER
ADDRESS
VMID
0
BIT
ADCEN
LABEL
internal
resistor
internal
resistor
0
DEFAULT
AGND
0 = ADC disabled
1 = ADC enabled
MB
PD, Rev 4.5, September 2008
DESCRIPTION
MBVSEL=0
MICBIAS
= 1.8 x VMID
= 0.9 X AVDD
MBVSEL=1
MICBIAS
= 1.3 x VMID
= 0.65 X AVDD
WM8974
rms
19
.

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