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I am getting the following waveform out of an 8-bit VDAC (each horizontal grid within the image corresponds to 2 \$\mu\$s and each vertical grid corresponds to 20 mV): enter image description here

I am using the DAC within a cypress microcontroller. A DC voltage is given to an ADC and then it is fed to a DAC so that I can check whether everything is working properly. Why are there periodic RC discharge like ripples coming at the output? Is there any way to eliminate it?

I used jumper wires to take the measurements. The output range of the VDAC is from 0 V to 1.02 V. These are the various parameters associated with the ADC:

enter image description here

This is the PCB: enter image description here

The connector (linear) with the 9 I/O pins was the one which I used. From the periodicity of the spikes, its frequency comes out to be 500 kHz.

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    \$\begingroup\$ 2ps/div!? I don't think that's quite right. Looks like your scope says 2μs/div. \$\endgroup\$
    – Polynomial
    Commented Mar 6, 2023 at 12:05
  • \$\begingroup\$ Can we see your hookup/pcb? \$\endgroup\$ Commented Mar 6, 2023 at 12:19
  • \$\begingroup\$ @Polynomial Sorry for the error. It is 2 us/div. \$\endgroup\$ Commented Mar 6, 2023 at 13:35
  • \$\begingroup\$ @ChristianidisVasileios I have added it. \$\endgroup\$ Commented Mar 6, 2023 at 13:43

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From the periodicity of the spikes, its frequency comes out to be 500 kHz.

That is incorrect 5 grids at 2 μs per grid is 100 kHz (the same as your conversion rate).

It looks like clock/latch feed-through (all DACs have it to some extent). The data sheet will tell you the amount (a quantity usually specified in nano-volt-seconds). Compare the waveform you have with your clock or data latch input to confirm the 100 kHz rates.

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  • \$\begingroup\$ Thank you. Is there any way to minimize it? \$\endgroup\$ Commented Mar 6, 2023 at 16:09
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    \$\begingroup\$ You could use a 2nd order low-pass filter on the DAC output to minimize it but, you have to be careful that it doesn't eat into the bandwidth of the real signals you are trying to output. In the past I've used 6th order DAC reconstruction filters to avoid eating into wanted bandwidth whilst cutting down on the conversion glitches. @Jonathan_the_seagull \$\endgroup\$
    – Andy aka
    Commented Mar 6, 2023 at 16:19
  • \$\begingroup\$ You might be able to add a few nF directly to the DAC output and 0 volts to get some beneficial effect. \$\endgroup\$
    – Andy aka
    Commented Mar 6, 2023 at 16:32

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