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PCM1822: Does AC-coupling the analog input pins violate the input voltage limitation of -0.3V?

Ted Hordeski
Prodigy 130 points
Part Number: PCM1822

The absolute maximum rating for the analog inputs to the ADC at the low end is -0.3V.  Recommended anlog input range is 0 to AVDD (+3.3V).  With a 2Vpp input, wouldn't AC-coupling cause the input signal to swing to -1V, violating the spec?

  • 0
    TI__Prodigy 220 points

    Hi Ted,

    The analog input voltage specs that you are referring to is for the analog input pins voltage to AVSS.

    If you scroll down to 7.5 Electrical Characteristics, you'll read that the Full-scale AC-coupled input signal is actually 1 Vrms, which is about 2.8 Vpp. You can also be reassured by the typical application shown in section 9.2, where you will find 1uF AC-coupling capacitors on each audio input. Hope this helps!

    Best,

    Andrew

  • 0 in reply to Andrew Ionascu
    Prodigy 130 points

    I still contend that table 7.1 is unclear regarding the Analog input voltage to AVSS (analog supply ground).   An AC-coupled 1Vrms signal will go below -0.3V.