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DAC7552: max output signal frequency

Remco Poelstra
Intellectual 985 points
Other Parts Discussed in Thread: DAC7552

Hi,


The datasheet states that the DAC7552 is suitable for waveform generation from DC to 10 kHz. The settling time is 5 μs, so I would expect it to be more like 100 kHz. What other parameter might limit the output waveform frequency?

Kind regards,

Remco Poelstra

  • 0
    TI__Genius 11750 points

    Howdy Remco,

    The update rate of a DAC usually is dominated by either setling time or SPI communication.  As you stated above, the datasheet states " The DAC7552 large-signal settling time is 5us, supporting an update rate of 200KSPS (200kHz). However, the update rates can exceed 1MSPS if the waveform to be generated consists of small voltage steps between consecutive DAC updates".  Basically, if you swinging from large code deltas (i.e. Full-scale to Zero scale), the DAC will be limited by this large-signal settling time, but if the delta between code changes is small it may be possible to have a smaller settling time allowing 1 MSPS or more.

    The large signal update rate is defined as: DACUpdateRate = (5us)+(1/SPI CLK Speed)*(Clock pulses) = 5us + (1/SPI CLK Speed)*16

    For a maximum SPI CLK of 50MHz, DACUpdateRate = 5.32us, or an update freq of 187KSPS

    Please be aware that the waveform generation (from DC to 10 kHz) is an estimate, as you will need multiple points to generate a sinusoidal signal or any other waveform.  The tradeoff for wave construction is resolution/granularity of the signal vs speed.

    Best Regards,

    Matt

  • 0 in reply to Matthew Sauceda
    Intellectual 985 points

    Hi,

    Thanks for your reply. Looks like my understanding of the specs is correct and I think I can use this part.

    Regards,

    Remco Poelstra