Max. Frequency of the ADuC7128/29 DDS

What is the max. output frequency from the on-chip DDS of the ADuC7128/29 ?

  • 0
    •  Analog Employees 
    on Jul 7, 2010 1:13 PM

    Basically this is related to the DDS settings and theoretically from this settings,

    as can be seen on page 47 in the datasheet, the frequency can be calculated.

    FSW = Frequency Select Word

    1 LSB in the 32-Bit DDSFRQ MMR is equal to 0.0048 Hz
    So the total range controllable by SW is from
        0.0048Hz to 20.8896MHz

    But the DAC output driven from the DDS has a subsequent Low-Pass-Filter (LPF) on the chip.
    This LPF determines the max. output frequency as specified in the datasheet on page 4
    to a -3dB cut-off point at 1MHz.