Hello!
General question regarding Isolators and Isolated Gate Drivers, I'm referring to app note SLLA284 "Digital Isolator Design Guide", section 4 "PCB Design Guidelines":
In fig. 4-1 it is shown in red colour (= mandatory for correct function as specified in data sheet?) to have no copper at all under the devices.
Questions:
- What are the exact technical reasons for this recommendation/requirement?
- Are they isolation related only (creepage etc, as described in the AN)?
- Or is a deterioration of operating parameters, especially CM transient immunity, to be expected?
- Does the internal construction of the devices (namely the very small coupling capacitors used for isolation) require that there is no conductive material in close proximity that will possibly add stray capacitance to the midpoint of the 2 caps in series? How sensitive is
I'm asking because in my application it is virtually impossible to have no conductors, more specific, planes under the isolator, but max dv/dt and max reliability is required. On the plus side, I only need functional insulation...
Thanks in advance, Jochen
