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PCM6240-Q1：Problems with DC common-mode difference settings.

user6504452
Prodigy 30 points
Part Number: PCM6240-Q1

1.When the PCM6240 uses MIC input, DC common-mode difference between 3.4V-5V can satisfy 2Vrms full range, if 10Vrms full range input is needed, in addition to register setting, DC common-mode difference between 3.4V-5V is also needed?

2.Does VBAT-IN have to be connected to BATT when using MICBIAS and Input Diagnostics functions?

On the one hand, if VBAT-IN must be connected to BATT, will the ADC chip stop working when the BATT voltage is 6V or less than 9V (MICBIAS voltage)? Still only registers report errors and ADC performance degrades.

On the other hand, if VBAT-IN can be disconnected without BATT, is the VBAT-IN pin float with a suspended or connected GND, and what is the recommended resistance if grounded?

Thanks and best regards,

Xinliang

  • 0
    TI__Mastermind 23050 points

    Hi Xianliang,

    There is a footnote that mentions "Microphone inputs support a 2 VRMS differential input full-scale AC signal voltage, if the CHx_MIC_RANGE register bit is set to low (default value). However, if the input DC common-mode differential voltage is higher than 4 V, then TI recommends setting the CHx_MIC_RANGE register bit high to avoid any saturation resulting from the high input DC common-mode differential voltage"

    You DC bias should be set according to your intended signal swing.

    You don't have to connect VBAT IN but the VBAT faults will not be valid then and should be masked. 

    If VBAT is less than MICBIAS this will register as a short to VBAT fault.

    VBAT is a high impedance input (~1MOhm), it can be left floating or connected to ground without issue.

    Best,

    Zak