DAC7311: Output high frequency harmonic problem

Hi Hao,

What is the output signal that the DAC7311 is producing? You mention you have a 4.5MHz SPI clock - what are you writing to the DAC?

Thanks,
Paul

Hi Paul,

The DAC7311 output is set to 0.9V, a constant voltage. Could you please help advise why there is high frequency harmonics? Thanks!

Best Regards!

Hao

Hi Hao,

The DAC7311 does not have any internal high-frequency functions.  You said you are not communicating with the DAC, so it should be in a steady-state and should not be contributing any harmonics.

Note that the reference for DAC is the power supply, so high-frequency noise on the power supply can be seen on the output.  Try measuring the power supply to see if you have the same harmonics.

Thanks,

Paul

Hi Paul,

The first picture is the power supply frequency spectrum, it can be seen that there is no obvious high frequency harmonics. However, the output has high frequency harmonics in the second picture, that's why I'm asking if you have any idea why it happens.

Thanks and Best Regards!

Hao

Hi Hao,

Sorry I missed the plot of the power supply.

Is there a cap load on the DAC output? Could it be oscillating?

To clarify, are you writing 0.9V repeatedly to the DAC, or do they only address the device once? What happens if they stop the SPI clock?

Thanks,

Paul