WM8768_10 Datasheet, PDF (36/38 Pages) Wolfson Microelectronics plc – 24-bit, 192kHz 8-Channel DAC

WM8768
Production Data
SUGGESTED ANALOGUE LOW PASS POST DAC FILTERS
It is recommended that a lowpass filter be applied to the output from each DAC channel 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 WM8768 produces much less high frequency output noise than normal sigma delta DACs. This
filter is typically also used to provide the 2x gain needed to provide the standard 2Vrms output level
from most consumer equipment. Figure 32 shows a suitable post DAC filter circuit, with 2x gain.
Alternative inverting filter architectures might also be used with as good results.
1.0nF
VOUT1L
10uF 1.8kΩ 7.5kΩ
51
47kΩ
VOUT1R
VOUT2L
VOUT2R
VOUT3L
VOUT3R
VOUT4L
VOUT4R
680pF
4.7kΩ
4.7kΩ
OP_FIL
OP_FIL
OP_FIL
OP_FIL
OP_FIL
OP_FIL
OP_FIL
OP_FIL
Figure 32 Recommended Post DAC Filter Circuit
w
PD Rev 4.3 July 2010
36