CMTI Improvement Circuit for Digital Isolator

This paper proposes an improved Common mode transient immunity (CMTI) circuit for digital isolator. SiO 2 film is used as the isolation dielectric for the digital isolator, and on-off keying (OOK) modulation is adopted as the methods of modulation and demodulation. At the same time, the input signal is transmitted as a fully differential signal. As one of the most important features of the isolator, poor CMTI performance will lead to wrong transmission when the voltage domain of transmitter (TX) or receiver (RX) changes. The CMTI performance can be improved by two aspects, i.e., firstly, reducing the offset of DC operating point. Secondly, increasing the common mode rejection ratio. This paper utilizes an active common mode filter circuit and a fully differential gate cross-coupled preamplifier to improve the CMTI performance to achieve 150 kV/us.