The device integrates a built-in, low-noise, programmable, high-voltage, microphone bias pin (MICBIAS) that can be used in the system for biasing the analog microphone. The integrated bias amplifier supports up to 80 mA of load current, which 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. The PCM62x0-Q1 have an integrated efficient boost converter to generate the high voltage supply for the programmable microphone bias using an external, low-voltage, 3.3-V BSTVDD supply. However, The PCM63x0-Q1 require an external high-voltage supply, HVDD, which requires at least 600 mV higher than the programmed microphone bias voltage and must be lower than 12 V.
When using the MICBIAS pin for biasing multiple microphones, TI recommends avoiding common impedance on the board layout for the MICBIAS connection to minimize coupling across microphones. Table 9 shows the available microphone bias programmable options.
|P0_R59_D[7:4] : MBIAS_VAL[3:0]||MICBIAS OUTPUT VOLTAGE|
|0000 to 0110||Reserved (do not use these settings)|
|0111||Set to 5.0 V|
|1000||Set to 5.5 V|
|1001||Set to 6.0 V|
|1010||Set to 6.5 V|
|1011||Set to 7.0 V|
|1100||Set to 7.5 V|
|1101||Set to 8.0 V|
|1110||Set to 8.5 V|
|1111||Set to 9.0 V|
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 GPIOx pins to directly control the microphone bias output power on or power off. This feature is useful in some systems to control the microphone directly without engaging the host for I2C or SPI communication. The MICBIAS_PDZ, P0_R117_D7 register bit value is ignored if the GPIOx pins are configured to control the microphone bias power on or power off.