• State TI Thinks Resolved
  • Locked Locked
  • Replies 7 replies
  • Answers 4 answers
  • Subscribers 30 subscribers
  • Views 187 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

PCM6340-Q1: MICBIAS voltage raise value

Zirui Su
Expert 5340 points
Part Number: PCM6340-Q1

Hi team

Here is a question we do not find the answer in the datasheet:

When the microphone input signal of the PMC6340Q1 chip is shorted to 18V battery, the MICBIAS voltage of the chip will be raised.

I know the normal programmable voltage value will up to 9V, while in the case above I do not know what MICBIAS voltage value will raise, 
Please confirm the maximum voltage that the MICBIAS voltage can withstand all the time, it is not marked in SPEC, it will be used for customer WCA analysis, thank you.

  • 0
    TI__Genius 13610 points

    Hello,

    You will need to be obeying this part of specs for input pins

    Best Regards,

    Carson

  • 0 in reply to Carson Allen
    TI__Expert 5340 points

    Hi Carson

    So do you mean the input max is just the MICBIAS(max)-0.1V which is about 9-0.1=8.9V?

  • 0 in reply to Zirui Su
    TI__Genius 13610 points

    Hello,

    Yes that is what dat sheet is indicating here.

    Best Regards,

    Carson

  • 0 in reply to Carson Allen
    TI__Expert 5340 points

    Hi Carson,

    Correct my question that:

    When customer short the output to battery with 14V, the phenomenon that the output of MICBIAS is only 9V, and the MICBIAS voltage will be raised due to this 14V or that is to say the MICBIAS voltage will be increased by the 14V. What is the maximum withstand voltage of MICBIAS? Customer would like to know under this circumstance the MICBIAS will increase up to what values of voltage, thank you.

  • 0 in reply to Zirui Su
    TI__Genius 13610 points

    Hello,

    You cannot short input to a level above MICBIAS when using microphone as input. MICBIAS is programmable output ,this is not a matter of what it can withstand because voltage at MICBIAS pin should not be changing at all due to a input, that is why resistor is supposed to be scaled accordingly to prevent that, but in this case you are just breaking device with a 14V level.

    Best Regards,

    Carson

  • 0 in reply to Carson Allen
    TI__Expert 5340 points

    Hi Cason,

    Thanks for your confirmation, I have checked with customer schematic that they have used the resistor divider to prevent the input higher than MICBIAS:

    Since customer has used MIC_IN short to 14V battery and see that at #2 the MICBIAS voltage has increased, I think in your previous reply according to this connection the device would be broken right? Customer would like to need a confirm that the MICBIAS pin will be broken or not, thanks.  

  • 0 in reply to Zirui Su
    TI__Genius 13610 points

    Hello,

    Well to see if it is actually broken I would put the input back to acceptable range and see MICBIAS returns to its programmed value, but shorting input to 14V could/would break a lot more than just MICBIAS when you are talking about the internal parts of the chip.

    Best Regards,

    Carson