SBASA91 December 2020 TLV320ADC3120
The device integrates a built-in, low-noise microphone bias pin that can be used in the system for biasing electret-condenser microphones or providing the supply to the MEMS analog or digital microphone. The integrated bias amplifier supports up to 20 mA of load current that can be used for multiple microphones and is designed to provide a combination of high PSRR, low noise, and programmable bias voltages to allow the biasing to be fine tuned for specific microphone combinations.
When using this MICBIAS pin for biasing or supplying to multiple microphones, avoid any common impedance on the board layout for the MICBIAS connection to minimize coupling across microphones. Table 8-11 shows the available microphone bias programmable options.
|P0_R59_D[6:4] : MBIAS_VAL[2:0]||P0_R59_D[1:0] : ADC_FSCALE[1:0]||MICBIAS OUTPUT VOLTAGE|
|000 (default)||00 (default)||2.75 V (same as the VREF output)|
|01||2.5 V (same as the VREF output)|
|10||1.375 V (same as the VREF output)|
|001||00 (default)||3.014 V (1.096 times the VREF output)|
|01||2.740 V (1.096 times the VREF output)|
|10||1.507 V (1.096 times the VREF output)|
|010 to 101||XX||Reserved (do not use these settings)|
|110||XX||Same as AVDD|
|111||XX||Reserved (do not use this setting)|
The microphone bias output can be powered on or powered off (default) by configuring the MICBIAS_PDZ, P0_R117_D7 register bit. Additionally, the device provides an option to configure the GPIO1 or GPIx pin to directly control the microphone bias output powering on or off. This feature is useful to control the microphone directly without engaging the host for I2C communication. The MICBIAS_PDZ, P0_R117_D7 register bit value is ignored if the GPIO1 or GPIx pin is configured to set the microphone bias on or off.