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Original question:

PCM6240-Q1: BSTOUT filtering cap

PCM6240-Q1: MICBIAS over current protection

Shinji Tsuji
Genius 12378 points
Part Number: PCM6240-Q1
Other Parts Discussed in Thread: PCM6340-Q1

Hi team,

Could you advise the behavior of MICBIAS output after PCM6340-Q1 detect over current threshold?

It is described in the datasheet that if MICBIAS load current exceed the limit threshold (82mA max), then the current will be limited.

Does it mean the MICBIAS continue to supply up to about 82mA max, but if the load impedance further decrease, the MICBIAS volage

will lose regulation and start to drop?

In that case, does MICBIAS continue to supply current until it hits the thermal protection limit?

Is there a MICBIAS under voltage threshold to shut it down before thermal shutdown?

regards,

  • 0
    TI__Mastermind 23050 points

    Hi Shinji-san,

    There are multiple micbias current flags. There are the user configurable thresholds, which do not limit current but only trigger an interrupt when the programmed threshold is exceeded. There is also the internal overcurrent protection circuit on MICBIAS which will limit the current if the overcurrent threshold is exceeded and the MICBIAS would lose regulation at this point. If the power dissipation is high enough it could trigger the thermal shutdown as well.

    Best,

    Zak

  • 0 in reply to Zak Kaye
    TI__Genius 12378 points

    Hi Zak,

    Thank you for your response.

    I would like to know if MICBIAS is potentially shutdown if the load impedance drops too low.

    I understand the MICBIAS lose regulation if it exceeds current protection limit, but as far as I understand, 

    current protection itself will not trigger MICBIAS shutdown until manually checks the flag and shutdown, correct?

    Regarding to the Thermal shutdown, it only shutdown MICBIAS/Boost and ADC sampling, correct?

    It will not initialize internal registers to its reset state, correct?

    regards,

  • 0 in reply to Shinji Tsuji
    TI__Mastermind 23050 points

    Hi Shinji-san.

    The overcurrent protection will not shutdown MICBIAS, only limit its output current. The thermal shutdown will turn off micbias and the boost and ADCs, but I believe the registers will not reset. Of course I would not recommend designing your circuit with the intention of entering thermal shutdown and would recommend a reset if this condition occurs anyways.

    Best,

    Zak

  • 0 in reply to Zak Kaye
    TI__Genius 12378 points

    Hi Zak,

    One more question about fault recovery. 

    PD_ON_FLT_RCV_CFG defines the behavior of AUTO/MANUAL recovery. 

    It is described about the ADC channels, but not about MICBIAS.

    If I set MICBIAS to power down at overtemperature condition as recommended, 

    does MICBIAS also automatically recover depends on PD_ON_FLT_RCV_CFG?

    regards,

  • 0 in reply to Shinji Tsuji
    TI__Mastermind 23050 points

    Hi Shinji-san,

    MICBIAS will not automatically recover if the overtemperature condition is still present. I need to confirm whether the PD_ON_FLT_RCV_CFG setting has any impact, but I do not believe it does for MICBIAS.

    Best,

    Zak