DAC1282: DC mode showes about 400mV swing when ouput 2.5V signal measured with oscilloscope

Hello Yang Yang2,

This post has a more in-depth explaination: https://e2e.ti.com/support/data-converters-group/data-converters/f/data-converters-forum/300939/output-ripple-issue-dac1282/1057291#1057291 

But to give more context, the DAC1282 was exclusively designed with the ADS1282 in mind. So much so, that we actually captured and quantified the DAC1282 specifications using the ADS1282. It was primarily designed as a test DAC to pair with this ADC. As a result, the designers actually designed the ADS1282 to filter out troublesome noise sources that were produced by the DAC. There's a quote in the linked post that says "The 256 kHz is the modulator clock frequency (CLK/16) and this frequency also corresponds to one of the SINC filter notches" to show an example of this fact, but I understand there are other design considerations that were considered to improve the DAC's performance with the ADS1282.     

So, what you're seeing is real, but the ADS1282 is designed so that the oscillation shouldn't be seen in the output. Thius is why we don't recommend the DAC1282 to be used in systems without the ADS1282. Hope this makes sense.

Best,

-Cole