O'Reilly logo

Digital Circuit Boards: Mach 1 GHz by Ralph Morrison

Stay ahead with the world's most comprehensive technology and business learning platform.

With Safari, you learn the way you learn best. Get unlimited access to videos, live online training, learning paths, books, tutorials, and more.

Start Free Trial

No credit card required

3.14 Ground Bounce

Ground bounce often refers to the voltage measured between two ground points on a circuit board. It may also refer to the voltage drop on the ground pin of an IC. Since it is not possible to contact the die, the total voltage drop cannot be observed. Our point of view is to consider that energy supplied to the IC flows in fields on transmission lines. The short section from the board to the die is not a match to the impedance presented by the ground and power plane. The reflections on this short segment of line cause fields that would be sensed by a probe in this area. To attribute this field to the ground connection alone would be an error.

Measurements are usually made using an oscilloscope probe where the probe common is connected to one ground point on the circuit board and the probe tip is connected to a second ground point. The voltage that is sensed is interpreted as an IR drop in the ground plane. The measure is usually made when there is some sort of problem involving signal integrity and the source of difficulty is under consideration.

The presence of a probe in a circuit means that a short stub has been added. We have shown that even short stubs added to a transmission line can affect rise time. When the probe is used to measure points along a ground plane, the measurement has little effect on any logic transition.

Any measure of voltage is a measure of an electromagnetic field. Because the probe tip and the probe common (ground) form a loop, the probe ...

With Safari, you learn the way you learn best. Get unlimited access to videos, live online training, learning paths, books, interactive tutorials, and more.

Start Free Trial

No credit card required