SLAS366 datasheet(15/58 Pages) TI2

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3–3

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 5–20. 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 pre-amp with

gain settings of 0/6/12/24 dB. This can be chosen by writing into bits D1–D0 of control register 5C.

TLV320AIC14

BIAS

MICIN

10 k

Ω

0.1

µF

Electret

Microphone

BIAS

MICIN

INM1

0.1

µF

10 k

Ω

0.1

µF

Electret

Microphone

(a) Single Ended

(b) Pseudo -Differential (High Quality)

Figure 3–1. Microphone Interface

3.3.2

INP and INM Input

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 3–2). 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.

INP1 or INP2

INM1 or INM2

1.35 V

TLV320AIC14

V(INP)

V(INM)

Figure 3–2. INP and INM Internal Self-Biased Circuit

3.3.3

Single-Ended Analog Input

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 3–3).

INP1 or INP2

INM1 or INM2

Analog Input

Figure 3–3. Single-Ended Input

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