Common-Mode voltages on ADuM3070 / ADuM4070

Document created by analog-archivist Employee on Feb 23, 2016
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We're making a test board for a very noise sensitive sensor. It has to be
galvanic isolted so we want to use the AdUM3070 or AdUM4070 for this. What is
the difference between these two? After the galvanic isolator we have LDO's to
remove some of the switching noise. Our sensor is very sensitive for
Common-Mode voltages. How is this regulators regarding this and is it necessary
to design in some common mode chokes? If so, do you have any recommandations on
which common mode chokes?

Do you have any other recommandations on how to minimize noise, using this
regulators? We will use the recommended design from the data sheet.

 

The ADuM3070/4070 are the same die set in different packages with creepage
differences to allow for the 2500V and 5000V isolation voltage ratings. The
noise performance should be the same for either part. I would recommend that
you add an RC snubber on each of the X1 and X2 switch nodes. A series network
of 14ohm and 330pF between each of X1 and X2 pins and GND1 will reduce the
ringing at each of these switch nodes. This also reduces the emissions. The
transformer isolation should help with common mode voltages.

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