The device supports simultaneous recording of up to two channels using the high-performance stereo ADC. The device consists of two pairs of analog input pins (INxP and INxM) which can be configured in single-ended or differential input mode by setting MD4 and MD5 pins. The input source for the analog pins can be from electret-condenser analog microphones, micro electrical-mechanical system (MEMS) analog microphones, or line-in (auxiliary) inputs from the system board.

The voice or audio signal inputs can be capacitively coupled (AC-coupled) or DC-coupled to the device. For best distortion performance, use of low-voltage coefficient capacitors for AC-coupling is recommended. The typical input impedance for the TAA5242 is 5 kΩ for the INxP or INxM pins with ±20% variation. The value of the coupling capacitor in AC-coupled mode must be chosen so that the high-pass filter formed by the coupling capacitor and the input impedance do not affect the signal content. Before proper recording can begin, this coupling capacitor must be charged up to the common-mode voltage at power-up. To enable quick charging, the device has a quick charge scheme to speed up the charging of the coupling capacitor at power-up when operating in I²S/LJ target mode. This input cap quick charge setting can be enabled by configuring the MD3 pin. The MD3 pin also configures the digital HPF cut-off frequency when the device is operating in I²S/LJ target mode.

For optimal performance, the common-mode variation at the device input should be limited to less than 100mVpp for AC-coupled settings. For applications that cannot avoid large common-mode fluctuations, the device offers the modes to configure the device for higher common-mode tolerance. Table 6-11 shows the analog input configuration modes available with MD4 and MD5 configuration.

Figure 6-8 to Figure 6-11 show the typical configuration diagrams for the various input configuration modes.

Figure 6-8 DC-Coupled Microphone or Line Differential Input Connection

Figure 6-9 DC-Coupled Microphone or Line Single-Ended Input Connection

Figure 6-10 AC-Coupled Microphone or Line Differential Input Connection

Figure 6-11 AC-Coupled Microphone or Line Single-Ended Input Connection

The device also supports channel select configurations to enable mono or stereo input in I²S and LJ Modes. This can be configured by setting MD6 pin. Table 6-12 shows the control for this feature with MD6 configuration. ADC Channel-2 is disabled when MD6 pin is set to High. In TDM mode, MD6 pin function is as described in Figure 6-2.