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ADC12J4000: when slightly over-driven does it wrap or saturate?

Other Parts Discussed in Thread: ADC12J4000

The ADC12J4000 datasheet describes the programmable over-range function in section 7.3.4.

My question concerns what happens when the device is over-driven.

What is the expected operation when the input drive is well below table 6.1 maximums, but the drive exceeds the level corresponding to +2047, or more negative than the level for -2048?

  • Hi David

    In over-drive conditions (ADC12J4000 datasheet Sections 6.1 Absolute Maximum Ratings and 6.3 Recommended Operating Conditions) the ADC output codes will saturate at the maximum (+2047) or minimum (-2048) code values. This ADC architecture does not exhibit any wrap-around behavior in over-drive.

    Best regards,

    Jim B

  • Jim,

    Excellent!

    I assume that when the DDC is not used that the limits are 0 and +4095.

    Thanks,
    Dave B
  • Hi David

    With DDC disabled the ADC12J4000 12 bit output can be formatted in offset binary (default) or signed 2s complement.

    Offset Binary

    Max = 4095 (1111 1111 1111)

    Min = 0 (0000 0000 0000)

    2's Complement

    Max = +2047 (0111 1111 1111)

    Min = -2048 (1000 0000 0000)

     

    With the DDC enabled, the complex data (15 bits I, 15 bits Q) is in signed 2s complement format.

    Maximum output code = 32767 (011 1111 1111 1111)

    Minimum output code = -32768 (100 0000 0000 0000)

    In all cases the 12 bit ADC core output (input to the DDC) will saturate during over-drive, There will be no wrapping or other unexpected output codes.

    Best regards,

    Jim B