Datasheet

ADAU1761
Rev. C | Page 30 of 92
Analog Microphone Inputs
For microphone inputs, configure the part in either stereo
pseudo-differential mode or stereo full differential mode.
The LINN and LINP pins are the inverting and noninverting
inputs for the left channel, respectively. The RINN and RINP
pins are the inverting and noninverting inputs for the right
channel, respectively.
For a differential microphone input, connect the positive signal
to the noninverting input of the PGA and the negative signal to
the inverting input of the PGA, as shown in Figure 33. The PGA
settings are controlled with Register R8 (left differential input
volume control register, Address 0x400E) and Register R9 (right
differential input volume control register, Address 0x400F). The
PGA must first be enabled by setting the RDEN and LDEN bits.
LEFT
MICROPHONE
LEFT
PGA
LDBOOST[1:0]
MUTE/
0dB/20dB
–12dB TO
+35.25dB
RIGHT
MICROPHONE
RIGHT
PGA
RDBOOST[1:0]
MUTE/
0dB/20dB
–12dB TO
+35.25dB
ADAU1761
LINP
LINN
RINN
MICBIAS
RINP
2k
2k
07680-052
Figure 33. Stereo Differential Microphone Configuration
The PGA can also be used for single-ended microphone inputs.
Connect LINP and/or RINP to the CM pin. In this configura-
tion, the signal connects to the inverting input of the PGA,
LINN and/or RINN, as shown in Figure 34.
LEFT
MICROPHONE
LEFT
PGA
LDBOOST[1:0]
MUTE/
0dB/20dB
–12dB TO
+35.25dB
RIGHT
MICROPHONE
RIGHT
PGA
RDBOOST[1:0]
MUTE/
0dB/20dB
–12dB TO
+35.25dB
ADAU1761
LINN
LINP
RINP
MICBIAS
RINN
CM
2k
2k
07680-053
Figure 34. Stereo Single-Ended Microphone Configuration
Analog Line Inputs
Line input signals can be accepted by any analog input. It is
possible to route signals on the RINN, RINP, LINN, and LINP
pins around the differential amplifier to their own amplifier and
to use these pins as single-ended line inputs by disabling the
LDEN and RDEN bits (Bit 0 in Register R8, Address 0x400E,
and Bit 0 in Register R9, Address 0x400F). Figure 35 depicts a
stereo single-ended line input using the RINN and LINN pins.
The LAUX and RAUX pins are single-ended line inputs. They
can be used together as a stereo single-ended auxiliary input, as
shown in Figure 35. These inputs can bypass the input gain
control, mixers, and ADCs to directly connect to the output
playback mixers (see auxiliary bypass in Figure 32).
ADAU1761
–12dB TO +6dB
LINNG[2:0]
LINN
LEFT LINE
INPUT
–12dB TO +6dB
RINNG[2:0]
RINN
RIGHT LINE
INPUT
LAUX
LEFT AUX
INPUT
RAUX
RIGHT AUX
INPUT
AUXILIARY
BYPASS
0
7680-054
Figure 35. Stereo Single-Ended Line Input with Stereo Auxiliary Bypass