Content originally posted in LPCWare by giusloq on Mon May 25 07:54:10 MST 2015
Quote: uLipe
So, you said the 3.3V rail supply is noisy too? Are checked with a scope the stage before your 3.3V supply? The issue can be there.
Battery 12V - 7805 - LPCXpresso board that generates 3.3V rail with another linear regulator. If I unplug the LPC board, the power supply rails (12V and 5V) seem good. When I plug the LPC board, I see the noise on 5V and even on 12V rails! How is this possible?
Quote: uLipe
Another tip is to load the DAC properly with the value based on datasheet (if I am correct is about to 1KOhm). Feed you DAC signal to a well designed low pass filter in order to remove the sampling spectral component, a butterworth with order about 2 can be sufficiente depending on your sample rate.
Can you post the DAC firmware section here? let-me remember you the DAC peripheral has a settling time which must be satisfied too, if you change the DAC value too fast (even if you writing the same value) some oscillations can ocurr until DAC enters in steady state.
I'm not sure, but I think the problem is with power supply noise and not on the DAC output itself.