ASAHI KASEI
[AK4564]
n
Digital EQ/HPF/LPF Circuits
The AK4564 performs equalizing, filtering and ALC (Automatic Level Control) by digital domain for A/D converter
data. The equalizing circuit emphasizes stereo separation when using internal microphone. LPF1, LPF2 and HPF2 are IIR
filters of 1st order to compensate frequency response of microphone and etc. HPF3 is IIR filter of 2nd order to cut a
wind-noise. Refer to the section of “ALC1 operation” about ALC1.
MIX
Main
LPF2
HPF2
ALC1
Lch
LPF1
HPF3
Lch
+
Sub
HPF1
HPF1
Sub
Rch
HPF3
LPF2
HPF2
ALC1
Rch
LPF1
+
MIX
Main
wind-noise cut
Filtering
Equalizing
Figure 21. Digital EQ/HPF/LPF
MS0140-E-01
2002/07
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