wm8782a Wolfson Microelectronics plc, wm8782a Datasheet - Page 10

• Manufacturer Part Number: wm8782a
• Description: 24-bit, 192khz Stereo Adc
• Manufacturer: Wolfson Microelectronics plc

WM8782A
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DEVICE DESCRIPTION
INTRODUCTION
ADC
ADC DIGITAL FILTER
The WM8782A is a stereo 24-bit ADC designed for demanding recording applications such as DVD
recorders, studio mixers, PVRs, and AV amplifiers. The WM8782A consists of stereo line level
inputs, followed by a sigma-delta modulator and digital filtering.
The device offers stereo line level inputs along with two control input pins (FORMAT, IWL) to allow
operation of the audio interface in three industry standard modes (left justified, right justified or I
An internal op-amp is integrated on the front end of the chip to accommodate analogue input signals
greater than 1V
The WM8782A offers Slave mode clocking schemes. The WM8782A supports master clock rates
from 128fs to 768fs and digital audio output word lengths from 16-24 bits. Sampling rates from 8kHz
to 192kHz are supported, delivering high SNR operating with 128x, 64x or 32x over-sampling,
according to the sample rate.
The line inputs are biased internally through the operational amplifier to V
The WM8782A uses a multi-bit over sampled sigma-delta ADC. A single channel of the ADC is
illustrated in Figure 3 Multi-Bit Oversampling Sigma Delta ADC Schematic.
Figure 3 Multi-Bit Oversampling Sigma Delta ADC Schematic
The use of multi-bit feedback and high oversampling rates reduces the effects of jitter and high
frequency noise.
The ADC Full Scale input is 1.0V rms at AVDD = 5.0 volts. Any input voltage greater than full scale
will possibly overload the ADC and cause distortion. Note that the full scale input has a linear
relationship with AVDD. The internal op-amp and appropriate resistors can be used to reduce signals
greater than 1Vrms before they reach the ADC.
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.
ADC OUTPUT PHASE
In the input to output data-path, the digital output data DOUT, is a phase inverted representation of
the analogue input signal.
The ADC digital filters contain a digital high pass filter. The high-pass filter response detailed in
Digital Filter Characteristics. The operation of the high pass filter removes residual DC offsets that
are present on the audio signal.
.
rms
. The device also has a high pass filter to remove residual DC offsets.
LIN/RIN
INTEGRATOR
ANALOG
MULTI
BITS
MID
.
TO ADC DIGITAL FILTERS
PD, April 2010, Rev 4.8
Production Data
2
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