MAX9888 Maxim Integrated Products, MAX9888 Datasheet - Page 81

• Manufacturer Part Number: MAX9888
• Description: Stereo Audio CODEC
• Manufacturer: Maxim Integrated Products

DataSheet.in
The IC playback signal path includes automatic level
control (ALC) and a 5-band parametric equalizer (EQ)
(Figure 19). 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.
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 20 shows an
example of ALC input vs. output curves.
Figure 19. Playback Path Signal Processing Block Diagram
PARAMETRIC
5-BAND
+
EQ
EQ1EN
EXCURSION LIMITER
DV1G:
0/6/12/18dB
DVEQ1:
0dB TO -15dB
MULTIBAND ALC
Playback Path Signal Processing
PARAMETRIC
DV2:
0dB TO -15dB DCB2
DV1:
0dB TO -15dB MODE1
5-BAND
EQ
EQ2EN
DVEQ2:
0dB TO -15dB
DVFLT
FILTERS
FILTERS
AUDIO/
AUDIO/
VOICE
Automatic Level Control
MIXDAL
MIXDAR
MIX
MIX
with FLEXSOUND Technology
DAREN
DALEN
DACL
DACR
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 20. ALC Input vs. Output Examples
Stereo Audio CODEC
OUTPUT SIGNAL
OUTPUT SIGNAL
OUTPUT SIGNAL
0
0
0
(dBFS)
(dBFS)
(dBFS)
THRESHOLD
THRESHOLD
THRESHOLD
LOW-LEVEL
LOW-LEVEL
LOW-LEVEL
ALC WITH ALCTH ≠ 000
ALC WITH ALCTH = 000
ALC DISABLED
-12
-12
-12
0
0
0
INPUT
SIGNAL
(dBFS)
INPUT
SIGNAL
(dBFS)
INPUT
SIGNAL
(dBFS)
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