Electrical connectors – With insulation other than conductor sheath – Plural-contact coupling part
Reexamination Certificate
2000-04-18
2001-08-14
Sircus, Brian (Department: 2839)
Electrical connectors
With insulation other than conductor sheath
Plural-contact coupling part
Reexamination Certificate
active
06273759
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a bus system using a multi-slot connector. More particularly, the present invention relates to a multi-slot connector having an integrated bus which connects a plurality of modules in a bus system.
Contemporary bus systems provide for the daisy chain connection of multiple modules on a motherboard. A conventional topology for connecting multiple modules is conceptually illustrated in FIG.
1
A. In this example, one or more connectors
11
are mounted on a motherboard
10
. Each connector
11
is adapted to hold a module
13
. Within this arrangement, modules
13
are sometimes termed “daughterboards” since each commonly holds one or more integrated circuits
14
.
In many contemporary bus systems, a bus runs between a controller
12
and a bus termination impedance
15
. The bus typically comprises multiple signal lines communicating data and/or control information between the controller and one or more of the integrated circuits on one or more of modules
13
. Controller
12
may take many forms including a microprocessor or a memory controller. The bus may range in size from a single signal line to a collection of complex signal line structures. The one or more integrated circuit(s)
14
on each module may be memory device(s) or logic device(s).
The increasing demand for data bandwidth from contemporary bus systems drives the development of impedance controlled buses within such systems. That is, increasing bus system clock speeds require carefully controlled signal line impedances in order to effectively communicate data and control information. At contemporary clock speeds, which already range above several hundred MHz, impedance mismatches on the bus will create unwanted signal reflections which act as noise signals on the bus. Recognizing the need to balance signal line impedances, conventional bus systems terminate the bus in a characteristic impedance
15
.
Data and control signals traversing the bus from controller
12
to termination impedance
15
travel the signal path
16
shown in FIG.
1
A. Of note, some portions of the signal path pass through the several connectors
11
and other portions of the path pass through the motherboard
10
. The transmission performance of such a “mixed” signal path has generally been acceptable in bus systems running a relatively lower frequencies. However, the transmission performance of this type of signal path has proved increasingly inadequate as bus system operating at higher frequencies.
In theory, the composition of the motherboard and the connectors mounted on the motherboard, as well as the signal line traces forming the bus, should produce a consistent impedance matched to termination impedance
15
. Actual practice is, however, far from theory. The motherboard is often manufactured by a different entity than the one manufacturing connectors
11
or modules
13
. In fact, the printed circuit boards (PCBs) commonly used as motherboards are notoriously variable in their final composition and implementation, and therefore their effective impedance. Further, motherboard impedances tend to vary from unit to unit depending on actual finished trace width, dielectric thickness and composition. As a result, signal path
16
shown in
FIG. 1A
often suffers from multiple impedance discontinuities caused by the signal path transitions from motherboard-to-connector, and from connector-to-motherboard.
SUMMARY OF THE INVENTION
The present invention provides an electrical connector having an integrated bus. Such a connector provides a signal path having a properly matched impedance. Unwanted signal reflections resulting from the impedance discontinuities inherent in the conventional bus system are significantly reduced with corresponding reductions in bus noise.
In one aspect, the electrical connector of the present invention includes a housing formed with a number of slots. Each slot is adapted to receive a module. Electrical contacts are placed between adjacent slots in the electrical connector, such that the combination of electrical contacts and inserted modules forms the integrated bus. Since inter-slot connections are not made through the motherboard, the noted impedance discontinuities do not arise.
The electrical contacts generally include electrical signal contacts and ground contacts. In one aspect, the electrical contacts are substantially formed within the housing of the electrical connector but include metal contacts which extend into adjacent slots to form a portion of the integrated bus.
In another aspect, the present invention provides a bus system including a motherboard having a high speed bus and an electrical connector with an integrated bus connected to the high speed bus. The electrical connector includes multiple slots, each adapted to receive a module and thereby connect the module to the high speed bus via the integrated bus. The plurality of modules thus connected may include a termination module, and/or a dummy module.
The bus may be terminated in a termination resistor found on the motherboard, the electrical connector, or a termination module inserted into the electrical connector. Alternatively, one or more of the modules may incorporate an integrated circuit having an electronically actuated termination resistor.
REFERENCES:
patent: 2904768 (1959-09-01), Rasmussen
patent: 4998886 (1991-03-01), Werner
patent: 5104324 (1992-04-01), Grabbe et al.
patent: 5186632 (1993-02-01), Horton et al.
patent: 5334962 (1994-08-01), Higgins et al.
patent: 5536177 (1996-07-01), Casey
patent: 5664968 (1997-09-01), Mickievicz
patent: 5812797 (1998-09-01), Crane, Jr. et al.
patent: 5827084 (1998-10-01), Biernath
patent: 5908333 (1999-06-01), Perino et al.
patent: 5928036 (1999-07-01), Thrush
patent: 6086427 (2000-07-01), Cahaly
patent: 0 436 943 A1 (1990-07-01), None
Gamini Nader
Perino Donald V.
Rambus Inc
Sircus Brian
Webb Brian S.
LandOfFree
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