I am testing my setup of MCP4725 DAC connected to MCP3221 ADC. DAC's output is connected to ADC's input. I'm measuring the difference between set values in DAC and measured values in ADC and I'm getting these strange patterns. Edit:x axis: values set in DAC (bits), y axis: DAC value - ADC value (bits)
Minimums and maximums are repeating every 128 bits. Also, errors shift from positive to negative going through the full range. I have tried different delays between setting DAC value and measuring ADC value and I get the same result. So I think it is not background noise.
I use REF3033 to power both ADC and DAC. But the same pattern is present when connecting them to LF33CV. Also, adding additional capacitors betwen input/output and ground doesn't change the pattern, just shifts it up or down.
Could you please help me figure out why is this happening and how to avoid it? I'm really sorry if this is something basic I'm missing here.