Datasheet

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MIC Input
TLV320AIC12 TLV320AIC12
BIAS
MICIN
10 kΩ
0.1 µF
Electret
Microphone
BIAS
MICIN
INM1
0.1 µF
10 kΩ
0.1 µF
Electret
Microphone
(a) Single Ended (b) Pseudo -Differential (High Quality)
INP and INM Input
INP1 or INP2
INM1 or INM2
1.35 V
TLV320AIC12
V
(INP)
V
(INM)
Single-Ended Analog Input
TLV320AIC12, TLV320AIC13
TLV320AIC14, TLV320AIC15
TLV320AIC12K, TLV320AIC14K
SLWS115E – OCTOBER 2001 – REVISED JANUARY 2007
Functional Description (continued)
TLV320AIC1x supports single ended microphone input. This can be used by connecting the external single
ended source through ac coupling to the MICIN pin. This channel is selected by writing 01 or 10 into bits D2-D1
in control register 6. The single ended input is supported in two modes.
Writing 01 into bits D2-D1 chooses self biased MICIN mode. In this mode, the device internally self-biases the
input at 1.35V. For best noise performance, the user should bias the microphone circuit using the BIAS voltage
generated by the device as shown in Figure 21 .
Writing 10 into bits D2-D1 chooses pseudo-differential MICIN mode. In this mode, the single ended input is
connected through ac-coupling to MICIN and the bias voltage used to generate the signal is also ac coupled to
INM1 as shown in Figure 22 . For best noise performance, the MICIN and INM1 lines must be routed in similar
fashion from the microphone to the device for noise cancellation.
For high quality performance, the single ended signal is converted internally into differential signal before being
converted. To improve the dynamic range with different types of microphones, the device supports a preamplifier
with gain settings of 0/6/12/24 dB. This can be chosen by writing into bits D1-D0 of control register 5C.
Figure 21. Microphone Interface
To produce common-mode rejection of unwanted signal performance, the analog signal is processed
differentially until it is converted to digital data. The signal applied to the terminals INM1/2 and INP1/2 are
differential to preserve device specifications (see Figure 22 ). The signal source driving analog inputs (INP1/2
and INM1/2) should have low source impedance for lowest noise performance and accuracy. To obtain
maximum dynamic range, the signal should be ac-coupled to the input terminal.
Figure 22. INP and INM Internal Self-Biased Circuit
The two differential inputs of (INP1/M1 and INP2/M2) can be configured to work as single-ended inputs by
connecting INP to the analog input and INM to ground (see Figure 23 ).
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