WM8766
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 WM8766 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 31 shows a suitable post DAC filter circuit, with 2x gain. Alternative inverting filter
architectures might also be used with as good results.
1.0nF
10uF
1.8kΩ
7.5kΩ
51
Ω
VOUT1L
10kΩ
680pF
4.7kΩ
4.7kΩ
OP_FIL
VOUT1R
VOUT2L
VOUT2R
VOUT3L
VOUT3R
OP_FIL
OP_FIL
OP_FIL
OP_FIL
OP_FIL
Figure 31 Recommended Post DAC Filter Circuit
PD Rev 4.1 July 2005
34
w
WOLFSON [ WOLFSON MICROELECTRONICS PLC ]
