Rainbow Electronics MAX98089 - Manual (Page 92)

���������������������������������������������������������������� Maxim Integrated Products 92
MAX98089
Low-Power, Stereo Audio Codec
with FlexSound Technology
Playback Path Signal Processing
The IC playback signal path includes automatic level
control (ALC) and a 5-band parametric equalizer (EQ)
(Figure 20). The DAI1 and DAI2 playback paths include
separate ALCs controlled by a single set of registers.
Two completely separate parametric EQs are included
for the DAI1 and DAI2 playback paths.
Automatic Level Control
The automatic level control (ALC) circuit ensures maxi-
mum signal amplitude without producing audible clip-
ping. This is accomplished by a variable gain stage that
works on a sample by sample basis to increase the gain
up to 12dB. A look-ahead circuit determines if the next
sample exceeds full scale and reduces the gain so that
the sample is exactly full scale.
A programmable low signal threshold determines the
minimum signal amplitude that is amplified. Select a
threshold that prevents the amplification of background
noise. When the signal level drops below the low signal
threshold, the ALC reduces the gain to 0dB until the sig-
nal increases above the threshold. Figure 21 shows an
example of ALC input vs. output curves.
The ALC can optionally be configured in dual-band
mode. In this mode, the input signal is filtered into two
bands with a 5kHz center frequency. Each band is
routed through independent ALCs and then summed
together. In multiband mode, both bands use the same
parameters.
Figure 21. ALC Input vs. Output Examples
Figure 20. Playback Path Signal Processing Block Diagram
0
OUTPUT SIGNAL
(dBFS)
OUTPUT SIGNAL
(dBFS)
OUTPUT SIGNAL
(dBFS)
INPUT
SIGNAL
(dBFS)
INPUT
SIGNAL
(dBFS)
INPUT
SIGNAL
(dBFS)
LOW-LEVEL
THRESHOLD
-12 0
LOW-LEVEL
THRESHOLD
-12 0
LOW-LEVEL
THRESHOLD
-12 0
0
0
ALC WITH ALCTH ≠ 000
ALC WITH ALCTH = 000
ALC DISABLED
EQ1EN EQ2EN
DVEQ1:
0dB TO -15dB
DV1G:
0/6/12/18dB
DV2:
0dB TO -15dB
DCB2
5-BAND
PARAMETRIC
EQ
5-BAND
PARAMETRIC
EQ
DVEQ2:
0dB TO -15dB
MULTI BAND ALC
EXCURSION LIMITER
DV1:
0dB TO -15dB
MODE1
DVFLT
DALEN
MIXDAR
DACL
DAREN
DACR
+
AUDIO/
FILTERS
AUDIO/
VOICE
FILTERS
MIX
MIXDAL
MIX