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PCM1865: maximum Ratings Analog Input

Daniel Fischer
Prodigy 20 points
Part Number: PCM1865


Tool/software:

hi, in the datasheet for the PCM1865 i see max analog Input +5V and -1.7V.
Are this max. electrical values or audio values the ADC can handle? If there is a short -2V value, is there just clipping or does the IC gets harmed?
If I have a microphone pre amp before, (like FIGURE 63: OPA1692 Low-Power, Low-Noise and Low-Distortion SoundPlus Audio Operational Amplifiers datasheet (Rev. C) )
do I need some limiter befor the analog input of the PCM1865?

second Question:
can the PCM1865 handle one single mono input? or do i need to generate a differential audio? ( Mic preamp is close to the IC on the same PCB)

If so, should i let the second pin floating?

thank you,

Daniel

  • +1
    TI__Mastermind 27670 points

    Hi,

    The absolute maximum ratings specified are for AC voltage, and most of our ADCs allow a bit of negative voltage to mitigate clipping. There are internal protection diodes that allow limited undershoot.

    However, if you suspect your analog input voltage to go beyond -1.7V this could forward bias the diodes and cause damage. You may need external clamping diodes in the input stage to limit voltage swings.

    You don't need a mic preamp for low level signals since there is a programmable gain amplifier integrated within the device. The device sets the common mode voltage when AC coupled and that capacitor will also remove any DC voltage.

    And yes you can provide a single-ended signal to PCM1865. The full scale range is 2.1Vrms when SE and not differential.

    .

  • 0 in reply to Daveon Douglas
    Prodigy 20 points

    thank you for the valuable information.
    I use this mic preamp mainly because of the 48V phantom power circuit.
    and for a professional audio interface, maybe I should use a preamplifier after all.
    So i will limit the input to max. +-1.5V