Even with an inherently robust isolator for
magnetic fields from TI, the surrounding system design deserves attention, because at board
level the loop areas are much larger than inside the isolator package:
- Minimize loop area on both sides of the
barrier. Route signal and return paths as tightly coupled pairs as the induced voltage is
directly proportional to enclosed loop area.
- Keep decoupling capacitors as close to
the supply pins as possible. The supply loop is often the largest loop near to the
isolator on the board.
- Avoid running signal traces parallel to
and directly beneath high-current conductors.
- Using differential signaling for anything
crossing a noisy region — magnetic coupling into a tight differential pair is largely
common-mode and gets rejected at receiver side.
- Remember that distance is a free margin
since field strength falls off rapidly with increasing distance; a few extra centimeters
from a strong magnetic field source is often more effective.