Backplane with power plane having a digital ground structure in signal regions
View Patent ↗For electrical backplanes and the like, a power plane adaptation to improve the propagation of high-speed signals through clearances in an embedded power plane is disclosed. In exemplary embodiments, the power plane is segmented in a high-speed connector region, such that a portion of the metal layer that forms the power plane is retained in the high-speed connector region—but isolated from the power-delivery portion of the power plane. The isolated portion is connected to digital ground, and clearances are formed therein where high-speed signaling throughholes will pass through the region. In some embodiments, various attainable advantages include better manufacturability, better matching and control of high-speed signaling throughhole impedance, and improved noise isolation. Other embodiments are described and claimed.
1. An electrical backplane comprising:
a plurality of high-speed signaling layers;
a plurality of primary power supply planes;
at least one digital ground plane interposed between the primary power supply planes and the high-speed signaling layers; and
a high-speed connector region on the backplane, the high-speed connector region comprising multiple conductive high-speed signaling throughholes and multiple conductive digital ground throughholes arranged on the backplane such that, on at least one of the primary power supply planes, the high-speed connector region comprises a first conductive plane section that is electrically isolated from a power supply section of the at least one of the power supply planes, the first conductive plane section electrically isolated from the high-speed signaling throughholes by clearances, the first conductive plane section electrically connected to at least one of the digital ground throughholes.
2. The electrical backplane of claim 1 , each of the primary power supply planes having a thickness at least as thick as an equivalent layer of three-ounce copper.
3. The electrical backplane of claim 1 , wherein the clearances separating the first conductive plane section from the high-speed signaling throughholes are of a size that allows the high-speed signaling throughholes to have approximately the same impedance where the high-speed signaling throughholes pass through the primary power supply planes as where the throughholes pass through the digital ground plane layers.
4. The electrical backplane of claim 1 , wherein the first conductive plane section completely surrounds each high-speed signaling throughhole in the high-speed connector region, the first conductive plane section separated from each high-speed signaling throughhole by a respective one of the clearances.
5. The electrical backplane of claim 1 , wherein each of the primary power supply planes comprises a conductive plane section in the high-speed connector region and separated from a power supply section of that power supply plane, the conductive plane section electrically isolated from the high-speed signaling throughholes by clearances, the conductive plane section electrically connected to at least one of the digital ground throughholes.
6. The electrical backplane of claim 5 , wherein the primary power supply planes comprise a first primary power plane, a first primary power return plane, a second primary power plane, and a second primary power return plane.
7. The electrical backplane of claim 1 , wherein the separation between the first conductive plane section and the power supply section of the power supply plane is at least twice as large as the clearances between the first conductive plane section and the high-speed signaling throughholes.
8. The electrical backplane of claim 1 , wherein at least one of the digital ground throughholes that is electrically connected to the first conductive plane section is also connected to the at least one digital ground plane.
9. The electrical backplane of claim 1 , further comprising power connector regions separate from the high-speed connector region but serving a common card slot on the backplane.