Improve digital feedthrough when using DAC's

Patrick Ruf

Hi,

I have a general question concerning digital feedthrough when unsing DAC's. Let's assume I have an ideal layout (which is not the case of course) and I want to further improve digital feedthrough.

Do the following changes improve digital feedthrough:

a) lower digital supply voltage from 5V to 3.3V
b) lower digital edge slope and lower ringing by introducing series resistors at the source of digital signals (in the range of 22 Ohm).

If so, how much can those changes improve the digital feedthrough? Is it worth doing it?

Thanks and best regards,

Patrick

over 2 years ago

0 Paul_Frost over 2 years ago

TI__Guru 53773 points

Hi Patrick,

I have a short video on this subject! https://training.ti.com/ti-precision-labs-dacs-digital-feedthrough

Generally, good grounding and very low supply impedance is needed. It also depends on the DAC: if you have a DAC with a dedicated DGND and AGND, you can do some isolation to help with this. You can also consider some output filtering to attenuate and smooth the digital feedthrough.

Thanks

Paul

0 Patrick Ruf over 2 years ago in reply to Paul_Frost

Genius 4965 points

Hi Paul,

Thanks for the inputs. I did view the video prior of writing this post.
But what do you think about the two measures in my post? Do you think they can help to improve the effect of digital feedthrough?

Regards,
Patrick

+1 Paul_Frost over 2 years ago in reply to Patrick Ruf

TI__Guru 53773 points

Hi Patrick,

Lowering the voltage and the digital edge slew rate will both help with digital crosstalk and feedthrough. I combinations of all these methods might be needed depending on the device and PCB layout.

Thanks,

Paul

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Improve digital feedthrough when using DAC's