WM8778_05 Datasheet, PDF (49/50 Pages) Wolfson Microelectronics plc – 24-bit, 192kHz Stereo CODEC

Production Data
WM8778
It is recommended that a low pass filter be applied to the output from the DAC for hi-fi applications.
Typically a second order filter is suitable and provides sufficient attenuation of high frequency
components (the unique low order, high bit count multi-bit sigma delta DAC structure used in
WM8778 produces much less high frequency output noise). This filter is typically also used to
provide the 2x gain needed to provide the standard 2Vrms output level from most consumer
equipment. Figure 34 shows a suitable post DAC filter circuit, with 2x gain. Alternative inverting filter
architectures might also be used with as good results.
4.7kΩ
4.7kΩ
+VS
_
51Ω
10uF
+
1.8kΩ
7.5KΩ
+
10kΩ
1.0nF
-VS
680pF
Figure 40 Recommended Post DAC Filter Circuit
w
PD Rev 4.0 April 2005
49