Conception of a digital isolator with an inductive integrated link

In this work, the conception of an integrated digital isolator in partnership with Cissoid is presented. This isolator is designed to be used in an isolated gate driver and to operate on a temperature range going from -40°C to 175°C which is 50°C higher than the market's standard. As it is designed to be used in an isolated gate driver, a point of major concern for this digital isolator will be its Common-Mode Transient Immunity (CMTI) which should at least be 50 kV/µs to fit with the market's standard. The isolation barrier chosen for this work is a micro-transformer provided by the foundry X-Fab for which a worst case model was developed. The self and mutual inductance of the transformer were computed analytically and verified using Comsol while the parasitic elements were estimated using the information provided by X-Fab's datasheet. To transfer data across this transformer, an emitter and a receiver communicating based on an On-Off-Keying (OOK) modulation architecture were developed. To limit the influence of the temperature on the system, a Common-Mode FeedBack (CMFB) which tunes the oscillation amplitude of the emitter was created while a matched current source was developed on the receiver side to limit the influence of the temperature. In the end, the developed digital isolator is able to work at a data rate of 2 Mbps with a maximum propagation delay of 26 ns and a maximum distortion of 11 ns. Even though these results are not as good as the ones from commercialized products, solutions will be presented in this work to improve these figures of merit for future work. Moreover, the CMTI of the developed circuit is limited due to a default in the architecture chosen in this work. Nevertheless, a solution will be suggested in order to solve this shortcoming as well.