I have used TC1796 as a micro-controller to read the voltage values, by using FADC. The read values are ok. However, the FADC signal has spikes, when the are incremental encoder signal (A and B) are fed into the microcontroller. The TC1796 only deals with 3.3 V. In the beginning, I found that the encoder signals are 0/5 V, then I have modified to 0/3.3V, but the noise (spikes) in FADC signal still exists. The spikes usually occurs while the shaft of encoder is being moved, especially when it is faster then the higher noises occur. I have done : - The zener-diode is connected before going to the FADC in order to protect the higher voltage. - Grounds are connected together. How should the spikes can be removed?