|  | 
 
 发表于 2011-6-20 14:28:38
|
显示全部楼层 
| Electrical ground1 looks simple on a schematic; unfortunately,
 the actual performance of a circuit is dictated by its printed-
 circuit-board (PCB) layout. What’s more, ground-node analysis is
 difficult, especially for dc-to-dc converters, such as buck and boost
 circuits, which pound the ground node with large, fast-changing
 currents. When the ground node moves, system performance
 suffers and the system radiates EMI. But a well-“grounded”
 understanding of the physics of ground noise can provide an
 intuitive sense for reducing the problem.
 Ground bounce can produce transients with amplitudes of volts;
 most often changing magnetic flux is the cause. A loop of wire
 carrying current is essentially an electromagnet whose field strength
 is proportional to the current. Magnetic flux is proportional to the
 magnetic field passing through the loop area,
 | 
 |