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DAC7716: Power supply to DVDD pin from ISOW7840 VISO output

MESH
Intellectual 870 points
Part Number: DAC7716
Other Parts Discussed in Thread: ISOW7840

Hello,

I considerring circuit board used DAC7716.
The power supply for IOVDD and DVDD on DAC7716 will supply from VISO output (3.3V) of digital isolator ISOW7840.  
ISOW7840 VISO output consist some voltage ripple. 

If the quality of the power supplied to the DVDD does not have a impact on the analog output of the dac7716, I am thinking of supplying power without additional LC filter circuits to DVDD. 
(Even in that case, 0.1 microfarad and 10 microfarad capacitor are added to the DVDD pin)

The ripple voltage of the ISOW7840 VISO output is about 100mVp-p.
(Based on the content of the ISOW7840 datasheet Figure 31)

Please advise me on the power supply from ISOW7840 VISO output to DVDD pin of DAC7716.

Regards,

MESH

  • +1
    TI__Mastermind 19086 points

    Hi,

    DAC7716 has seperate analog power supplies AVDD and AVSS. Analog ouput noise performance is determined by the noise on these power supply and the reference.Having said that, if there is excessive noise on the digital lines, it can couple through the system and you can have noise in the analog output. This heavily depends on the layout of the board and DAC section.100mVpp is on the higher side, we didnt verify the DAC performance with this kind of noise on the digital power supply.

    With proper layout we can minimise most of these errors. Have a look at the digital feedthrough video below to undertsand more on this effect.

    https://training.ti.com/ti-precision-labs-dacs-digital-feedthrough

    If possible have additional filters for DVDD.

    Regards,

    AK

  • 0 in reply to Akhilesh K
    Intellectual 870 points

    Hi Akhilesh K

    Thank you for your reply.

    I would also consider adding a additional filter as an option.

    Regards,

    MESH

  • 0 in reply to MESH
    TI__Mastermind 19086 points

    Hi,

    Thanks for considering DAC7716. Let me know if you need any additional help.

    I am closing this thread, feel free to open another if you have any other questions.

    Regards,

    AK