ADuM6401 and common mode transient immunity

Document created by analog-archivist Employee on Feb 23, 2016
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On my measurement board there are some analog inputs that should be galvanic
insulated from the rest of the board. So I want to use the ADUM6402. A
requirement for our design is that it can handle a surge pulse (common mode,
line - earth) with 4kV amplitude without destruction of the board. In our
design, the secondary side of the ADUM6402 will see the surge pulse (lift up
the voltage level of the whole circuit (common mode)). Can the ADUM6402
withstand this pulse voltage (voltage is rising up very fast). In the data
sheet there is something written about the transient voltages; does it mean
burst pulses (low energy) or is it also valid for surge pulses (high energy) ?

 

The energy in the pulses does not really effect the withstand capability of the
part, since it is an isolation device, the voltage will appear across the
barrier, but almost no current can couple so only the voltage profile is of
interest. With the standard 1.2uS/50uS lightning surge the ADuM6401 should
survive up to 8kV surges without breakdown of the isolation barrier. So the 4kV
surges are not an issue. The parameter in the data sheet is CMTI (common mode
transient immunity) which is rated as 100kV/us before damage could occur, and
that is induced voltages causing latch-up, it is not a failure of the isolation
barrier. That slew rate is well below surge slew rates. Some fast transient
tests violate the 100kV/us rate, but it is a very conservative limit, and we
have not seen issues.

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