Hello,
I am wondering if there are any recommendations or considerations one should have around the validity of measurements when changing the CAPDAC on the FDC1004.
Or in other words - can changing the CAPDAC have an impact on the measurement such that we should wait some amount of time before considering the measurements valid? Should the CAPDAC only be changed while all measurements are stopped? or can we change it while measurements are being continuously taken?
Currently in our application, we are measuring continuously (i.e. FDC_CONF REPEAT enabled). While measuring, if deemed necessary the CAPDAC is incremented, however, we are not currently stopping the measurement, just setting a new CAPDAC value with the CONF_MEASx register while the measurement is running.
Under certain circumstances, we are noticing oscillations after changing CAPDAC values. My hypothesis is that the CAPDAC change is impacting the measurement, causing our algorithm to think the offset must be adjusted which then triggers further CAPDAC changes, etc
I am thinking this because in the data sheet I see "The CAPDAC can be viewed as a negative capacitance connected internally to the CINn pin". If we were to suddenly add a negative capacitance to the circuit being measured, depending on the properties of the circuit, I would expect a transition time between the steady state of the circuit with different negative capacitance values applied - But I don't know if this sentence is just to help understand the function of the CAPDAC or actually represents what is physically happening in the internal circuit.
Thank you,
David
