8.2.2 Two-Channel Microphone Input for Automotive Infotainment Systems

The high CMRR, low-noise, and ease-of-use in single supply applications make the INA165x-Q1 an excellent choice for applications in automotive infotainment systems. Figure 60 illustrates a high-CMRR input circuit for in-cabin microphones used for hands-free phone systems. The microphones are connected with matched bias resistors, R_BIAS, to preserve the high-CMRR performance of the INA165x-Q1. The exact value of the microphone bias voltage, V_BIAS, and the R_BIAS resistors depends on the particular microphones used. Bandwidth-limiting the audio signal to the range of frequencies for speech is common in hands-free systems. As shown in Figure 60, all filtering components are placed at the output of the INA165x-Q1 rather than the input to preserve high CMRR. The values shown in Figure 60 limit the signal bandwidth to approximately 100 Hz to 10 kHz.

Figure 60. Two-channel Microphone Input for Automotive Infotainment Systems