Datasheet

ADAU1761
Rev. C | Page 29 of 92
RECORD SIGNAL PATH
LINP
LINN
LAUX
LEFT
ADC
RIGHT
ADC
JACKDET/MICIN
RAUX
MICIN LEFT
MICIN RIGHT
INSEL
INSEL
ALCSEL[2:0]
ALC
CONTROL
AUXILIARY
BYPASS
MX1AUXG[2:0]
LDVOL[5:0]
LINNG[2:0]
LINPG[2:0]
LDBOOST[1:0]
MIXER 1
(LEFT RECORD
MIXER)
MIXER 1
OUTPUT
(TO PLAYBACK
MIXER)
MIXER 2
OUTPUT
(TO PLAYBACK
MIXER)
–12dB TO +6dB
–12dB TO +6dB
MUTE/0dB/20dB
PGA
DECIMATOR/
ALC/
DIGITAL
VOLUME
DIGITAL
MICROPHONE
INTERFACE
MIXER 2
(RIGHT RECORD
MIXER)
–12dB TO +6dB
MX2AUXG[2:0]
–12dB TO +6dB
–12dB TO
+35.25dB
RINN
RINP
ALCSEL[2:0]
ALC
CONTROL
RDVOL[5:0]
RINPG[2:0]
RINNG[2:0]
RDBOOST[1:0]
–12dB TO +6dB
–12dB TO +6dB
MUTE/0dB/20dB
PGA
–12dB TO
+35.25dB
07680-022
Figure 32. Record Signal Path
INPUT SIGNAL PATHS
The ADAU1761 can accept both line level and microphone
inputs. The analog inputs can be configured in a single-ended
or differential configuration. There is also an input for a digital
microphone. The analog inputs are biased at AVDD/2. Unused
input pins should be connected to CM.
Each of the six analog inputs has individual gain controls (boost
or cut). The input signals are mixed and routed to an ADC. The
mixed input signals can also bypass the ADCs and be routed
directly to the playback mixers. Left channel inputs are mixed
before the left ADC; however, it is possible to route the mixed
analog signal around the ADC and output it into a left or right
output channel. The same capabilities apply to the right channel
and the right ADC.
Signals are inverted through the PGAs and the mixers. The
result of this inversion is that differential signals input through
the PGA are output from the ADCs at the same polarity as they
are input. Single-ended inputs that pass through the mixer but
not through the PGA are inverted. The ADCs are noninverting.
The input impedance of the analog inputs varies with the gain
of the PGA. This impedance ranges from 1.7 k at the 35.25 dB
gain setting to 80.4 k at the −12 dB setting. This range is shown
in Figure 25.