Electronic digital logic circuitry – Interface – Current driving
Reexamination Certificate
2001-05-24
2002-09-17
Tokar, Michael (Department: 2819)
Electronic digital logic circuitry
Interface
Current driving
C326S090000, C326S030000, C710S108000, C710S120000, C375S257000
Reexamination Certificate
active
06452420
ABSTRACT:
FIELD OF THE INVENTION
The present invention is related to differential signaling techniques, and more specifically to differential signaling for electronic circuits.
BACKGROUND OF THE INVENTION
Differential signaling has been in existence for many years. For example, teletypes were some of the first equipment to use differential signaling to communicate. One common technique of differential signaling utilizes a current loop to send and receive information between a receiver and transmitter.
According to this differential signaling technique, current is sent in one direction around the loop or the other direction around the loop to represent information. A pulse of current on the loop may correspond to a logic value of “1”, while no current may correspond to a logic value of “0.”
Current loops have several advantages over other signaling techniques. For example, data sent utilizing a current loop can travel further than data sent through a common RS-232 interfaces. Current loop differential signaling techniques also provide protection against electrical interference. Additionally, current loop differential signaling techniques can reliably make connections when other communication techniques cannot.
One type of a current loop differential signaling technique is Low Voltage Differential Signaling (LVDS). LVDS is a differential signaling technique commonly used in data transmission systems. A low voltage differential signal produced by a line driver typically has peak-to-peak amplitudes in the range from 250 mV to 450 mV. The low voltage swing minimizes power dissipation, while maintaining high transmission speeds. Typical transmission speeds are over 100 Mbps (Mega-bits per second).
Electronic devices (i.e. computers) often have a local port that is a connection terminal for a remote port. When a remote port is connected to the local port, the local port is initialized to recognize the remote port. After initialization, the remote port and the local port can exchange information. The communication between the ports is often done by means of LVDS driver and receiver pairs.
SUMMARY OF THE INVENTION
Briefly described, the present invention is directed at providing a multi-dimensional differential signaling (MDDS) system.
According to one aspect of the invention, an MDDS system includes N communication lines. The MDDS system may be two-dimensional or multi-dimensional. For example, the system may include three communication lines forming three differential pairs. The number of communications lines chosen for the MDDS system affects the number of differential pairs in the system as well as the bits of information that may be transmitted.
According to another aspect of the invention, more than two states are provided by the MDDS system. For example, if three communication lines are used within the MDDS system, six states are provided. If twelve states are desired then four communication lines may be implemented in the MDDS system.
According to another aspect of the invention, a load to provide the differential across the communication lines is provided by a star or a delta load.
REFERENCES:
patent: 4631428 (1986-12-01), Grimes
patent: 5604450 (1997-02-01), Borkar et al.
patent: 6208161 (2001-03-01), Suda
patent: 6226330 (2001-05-01), Mansur
Engineering Formulas, 6thEdition, Kurt & Reiner Gieck, Electrical Engineering, S10.
Merchant & Gould P.C.
National Semiconductor Corporation
Sullivan Timothy P.
Tan Vibol
Tokar Michael
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