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DAC43608: Output Fluctuaiton

Part Number: DAC43608

Hi there,

My customer is evaluating DAC43608. And he got a waveform like below.

The blue wave is 3.3V power supply, which is slightly fluctuating. VrefIN is connected to this power supply. 

The pink wave is 0V output. Why output is also fluctuating and has a phase shift between power supply? It should be straight as GND. Do we have any method to cancel the noise?

Also, he is using DEVICE_CONFIG register to turn off/on the output. Turn on output then modify output value, or modify output value then turn on the output, which is the better sequence?

Best,

Zeming

  • Hi,

    Since Vrefin is connected to this supply, all the noise present in the supply will be coupled to output as well. To avoid this, only solution is connect a proper clean reference to device.

    Also looks like this supply is coming from a switching power supply. Please use LC filters or Pi filters to reduce the ripple voltage.

    As far is sequence is concerned, it doesn't matter. First clean up power supply and provide proper reference voltage to device.

    Regards,

    AK

  • Hi AK,

    Thanks a lot.

    The customer will try to use a clean REF.

    Additionally, could you explain why there is a phase shift between input and output? 

    Best,

    Zeming

  • Hi AK,

    Do you have any idea why there is a phase shift between input and output?

    I would be very grateful if you could explain.

    Best,

    Zeming

  • Hi,

    On the reference pin, we may have filters formed by the decoupling capacitors and bond resistance and inductors, there can be phase shift for AC signals. 

    This phase shift can be a function of the frequency, value of the decoupling capacitors, inductance and resistance of bond wires etc.

    We don't expect customer to give AC signals for this device on REF pin. Device expects a clean DC signal.

    Hope this clarifies your query,

    Regards,

    AK