Hi,
The zero drift phenomenon and fluctuations in the ADC values when nothing is connected to the GPIOx pins of the MC33772B can be attributed to several factors.
When GPIO pins are not connected to any specific signal (left floating), they can pick up noise from the surrounding environment. This noise can cause the ADC readings to fluctuate significantly. Floating inputs can act like antennas, capturing electromagnetic interference from nearby components or power lines. High impedance inputs are more susceptible to noise, leading to fluctuations in the ADC readings.
Poor PCB layout can lead to crosstalk between signal traces or inadequate grounding, introducing noise into the ADC inputs. Proper grounding and separation of analog and digital signals are crucial for stable ADC readings.
External electromagnetic interference (EMI) from other electronic devices or environmental sources can affect the ADC readings. Shielding the circuit or improving the grounding can help mitigate this interference.
By addressing these factors, you should be able to reduce or eliminate the zero drift phenomenon and stabilize the ADC readings of the MC33772B.
BRs, Tomas
