Electricity: power supply or regulation systems – Self-regulating – Using a three or more terminal semiconductive device as the...
Reexamination Certificate
1999-07-27
2001-01-30
Nguyen, Matthew (Department: 2838)
Electricity: power supply or regulation systems
Self-regulating
Using a three or more terminal semiconductive device as the...
Reexamination Certificate
active
06181122
ABSTRACT:
FIELD OF THE INVENTION
The present invention generally relates to circuits for supplying reference voltages and bias currents. More specifically, the invention is related to a new and efficient start-up circuit for starting voltage and current controlled elements.
BACKGROUND OF THE INVENTION
Present circuit fabrication lends itself to the creation of integrated circuits requiring biasing and initiation by a specific current or voltage value. To help bias and initiate these integrated circuits, self-biasing circuits, often called band-gap reference circuits (band-gaps), are implemented.
Band-gaps are used in a variety of integrated circuit devices as a means for generating a temperature and supply independent reference voltage, as well as a temperature and supply independent current. The band-gap provides the rest of the chip upon which it is situated with reference voltages and currents. Hence, if the band-gap doesn't start up on its own, the entire chip, and the system it is connected to, may fail to operate.
Therefore, a critical issue in the design of band-gaps is ensuring that the band-gap starts promptly and that any chance of the band-gap not starting is significantly reduced, if not eliminated altogether. To fulfill these requirements, start-up circuitry is implemented.
Several known techniques are presumably utilized to start band-gaps. Amongst these, conventional approaches have attempted to design a solution to force the self-biased circuit out of any low power state, which will not allow the self-biased circuit to start, by utilizing devices which are capable of functioning with low power. This, however, is very difficult and highly unreliable, as the properties of the low power devices cannot be properly modeled by simulation programs in this low power mode due to the simulation programs being generally incapable of accepting such low power values for parameter requirements.
Therefore, there is a need for a reliable and efficient method for initiating bandgaps.
SUMMARY OF THE INVENTION
Briefly described, the invention provides a system and method for providing a significant amount of current or voltage to a voltage and current controlled element when the element is operating in a low power mode, thereby ensuring that the element properly turns on.
Generally, the preferred embodiment of the invention comprises a voltage and current controlled element which, in normal mode, is powered by a power source, via a driving element. Within the voltage and current controlled element, a current loop is maintained, thereby causing a constant current value throughout the voltage and current controlled element and allowing the voltage and current controlled element to output a temperature independent voltage level of approximately 1.25 volts.
If, however, the voltage received from the power source is below a threshold voltage, set within the driving element, the driving element forces a large amount of current to the voltage and current controlled element. This forced current turns on the voltage and current controlled element and causes it to function as if the power source voltage was above the threshold voltage. Therefore, the voltage and current controlled element locks in an active operating point and emits approximately 1.25 volts. This eliminates the possibility of the voltage and current controlled element locking up in a low power mode.
In accordance with the preferred embodiment of the invention, an amplifier, located within the voltage and current controlled element, outputs the current value which is mirrored throughout the voltage and current controlled element, until the current loop is completed.
The invention has numerous advantages, a few of which are delineated hereafter as examples. Note that the embodiments of the invention described herein possess one or more, but not necessarily all, of the advantages set out hereafter.
One advantage of the invention is that it provides a simple and reliable procedure to prevent a self-biased circuit from locking in a low power mode.
Another advantage of the present invention is that it provides a start-up solution to band-gap failure in an area where assumption of the properties of devices used by the band-gap during low power mode, for purposes of simulating a solution to the band-gap's failure, would be otherwise be improper.
Another advantage of the present invention is that it can be utilized to reliably start-up any dormant node in a circuit which is locked at a significantly different voltage level as compared to an intended voltage level, with the mere addition of at least one current driving device.
Other objects, features, and advantages of the present invention will become apparent to one of reasonable skill in the art upon examination of the following drawings and detailed description. It is intended that all such additional objects, features, and advantages be included herein within the scope of the present invention, as defined by the claims.
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Larsen Frode
Tan Nianxiong
Globespan, Inc.
Nguyen Matthew
Thomas Kayden Horstemeyer & Risley
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