Isolated Gate Drivers & Noise Immunity

The CMTI or dv/dt showdown between gate drive optocouplers, ACPL-P349 from Broadcom and ISOdriver, Si827x from Silabs, to meet today’s high frequency applications when using SiC or GaN MOSFET. In power electronics, isolated gate drivers are used to drive IGBT and Power MOSFETs. With the emergence of SiC and GaN, power electronics are operating at higher frequencies to increase system efficiency and reduce system size and costs. The increase in frequency results in higher switching noise or commonly known as common mode transient, dv/dt. This noise can be coupled to the input and cause wrong output at the power semiconductors.

One important specification of the gate driver is its ability to reject high common mode transient.  This specification is normally termed as CMTI, Common Mode Transient Immunity. To meet high frequency applications when using SiC or GaN MOSFET, it is recommended to have a CMTI of at least 100kV/µs. As the frequency increases, the CMTI is expected to double to 200 kV/µs. Now, let’s take a look at the CMTI performance of two isolated gate drivers, ISOdriver Si827x from Silabs and optocoupler ACPL-P349 from Broadcom that have CMTI of more than 100kV/µs.