Miscellaneous active electrical nonlinear devices – circuits – and – Signal converting – shaping – or generating – Particular stable state circuit
Reexamination Certificate
1999-10-28
2001-10-02
Lam, Tuan T. (Department: 2816)
Miscellaneous active electrical nonlinear devices, circuits, and
Signal converting, shaping, or generating
Particular stable state circuit
C327S538000, C327S541000, C323S314000
Reexamination Certificate
active
06297678
ABSTRACT:
BACKGROUND
1. Field of the Present Invention
The present invention generally relates to the field of electronic systems and more particularly to an externally supplied circuit for rapidly precharging system nets.
2. History of Related Art
In the design of an electronic system, such as a circuit board populated with a plurality integrated circuit devices that are interconnected with a matrix of interconnects or “nets,” it is desirable to precharge the net to a logical level such as the logical high level when the net is tri-stated. Precharging the net can improve system performance by reducing the time required for the net to transition from a high impedance state to a logical high state. If the tri-state voltage is close to or equal the logical high voltage, it will be appreciated that less time is required to transition the signal from the tri-state condition to the logical high condition. Preferably, the precharging circuitry is embedded in the drivers of the devices coupled to the net. Unfortunately, however, not all devices are designed and implemented with drivers incorporating adequate precharging circuitry. When such “non-conforming” devices are connected to a system net, problems in achieving a desired transition time may arise. More specifically, after a non-conforming device releases control of the net, the net may be in a partially or fully charged state such as a voltage intermediate between the logical high and logical low level. When the net is subsequently driven to a logical level, the amount of time required to transition the net may be in excess of the time permitted by the system timing constraints and the system may incorrectly interpret a logical level on the net. Compounding this problem are the significant difficulties and expense associated with attempting to rework or replace the non-conforming devices. Accordingly, it would be highly desirable to implement a solution that would enable adequate pre-charging of selected system nets without requiring modification of the existing devices.
SUMMARY OF THE INVENTION
The problems identified above are in large part addressed by an electronic system, precharge circuit, and method for precharging system nets according to the present invention. The system includes a plurality of devices. Each of the devices includes at least one I/O pin driven by a driver circuit. The system further includes a system net connected to at least one of the I/O pins of each of the plurality of devices. A precharge circuit suitable for connecting to the system net is provided. The precharge circuit includes a sense stage and a charging stage. The sense stage is configured to receive the system net voltage as an input and adapted to sense a system net voltage transition. The charging stage is connected to the system net and configured to receive an output of the sense stage. The sense stage is configured to activate the charging stage in response to detecting a system net voltage transition. The charging stage, upon activation, is configured to provide a current path between a supply voltage and the system net for a specified duration. After the specified duration, the current path is disabled. With this mechanism, the invention assists in rapidly charging a system net when a transition is sensed by providing a current amplified, low impedance path between the power supply and the system net for a duration sufficient to pre-charge the system net.
REFERENCES:
patent: 5153457 (1992-10-01), Martin
patent: 5489861 (1996-02-01), Seymour
International Business Machines - Corporation
Lally Joseph P.
Lam Tuan T.
McBurney Mark E.
Nguyen Minh
LandOfFree
Circuit for rapidly charging a system net does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Circuit for rapidly charging a system net, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Circuit for rapidly charging a system net will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2584461