Active solid-state devices (e.g. – transistors – solid-state diode – Housing or package – With contact or lead
Reexamination Certificate
2001-03-15
2002-05-28
Clark, Sheila V. (Department: 2815)
Active solid-state devices (e.g., transistors, solid-state diode
Housing or package
With contact or lead
C257S723000, C257S724000, C438S107000
Reexamination Certificate
active
06396137
ABSTRACT:
PARTIAL WAIVER OF COPYRIGHT
All of the material in this patent application is subject to copyright protection under the copyright laws of the United States and of other countries. As of the first effective filing date of the present application, this material is protected as unpublished material.
However, permission to copy this material is hereby granted to the extent that the copyright owner has no objection to the facsimile reproduction by anyone of the patent documentation or patent disclosure, as it appears in the United States Patent and Trademark Office patent file or records, but otherwise reserves all copyright rights whatsoever.
FIELD OF THE INVENTION
The present invention relates generally to the regulation and/or switching of voltage and/or current and/or power as applied to integrated circuits.
BACKGROUND OF THE INVENTION
General System Block Diagram (
0100
)
The basic problem addressed by the present invention can be best illustrated by reference to the block diagram of FIG.
1
. Here it can be seen that a non-ideal voltage source (
0101
) is used to provide a current (I
VS
) to a complex load (
0103
) through a voltage/current/power regulator/switch (VCPRS) module (
0102
). It is important to note that the same non-ideal voltage source (
0101
) may simultaneously supply a variety of other loads (
0106
) through other VCPRS modules (
0105
) within the context of the entire system environment. The ground reference (
0104
) for the entire system is typically common but need not necessarily be so in all circumstances.
Regulator Function
The primary function in many system contexts is for the voltage/current/power regulator module (
0102
) to regulate the output voltage supplied to the complex load (
0103
) so that it is constant under all loading conditions and also under all conditions of the non-ideal voltage source (
0101
). While the typical context of this regulation scheme is one of constant output voltage, there are applications in which a constant output current (or constant output power) are desired, and this discussion applies equally well to these environments.
Voltage Regulation
Typically the voltage transformation from the non-ideal voltage source (
0101
) to the complex load (
0103
) can occur via dissipation in the VCPRS module (
0102
) (linear voltage regulation), or may occur within the context of a buck/boost voltage converter in which the voltage regulator/switch acts more strictly as a power converter with regulated output voltage and/or current. Neither configuration limits the teachings of the present invention, as the form of voltage/current regulation in both cases requires some common circuit elements that are the subject of the teachings herein. Therefore, it is sufficient to realize that the regulator function served by the VCPRS function (
0102
) is one of meeting the demands (voltage, current, power) to the load based on a specified regulation scheme.
As an example, the typical voltage regulation requirements for a modern microprocessor range from ±10% to ±5%, which for a 1.5V core voltage means a ±150 mV to ±75 mV regulation range. This is in stark contrast to the ±500 mV regulation range typically permitted for older 5V digital logic systems. A significant reason for limiting the regulation drift of a microprocessor power supply voltage (VDD) is one of reliability. As the gate oxide thickness of modern CMOS processes are reduced, the susceptibility to oxide punchthrough is increased and thus regulation of the power supply becomes a paramount reliability consideration.
Voltage Dropout
The issue of voltage regulation is tightly related to another concept termed voltage dropout. As stated in the literature:
“The dropout voltage is the voltage at which the input voltage is low enough to cause the output to go out of regulation. With the reduction of logic voltages, the dropout voltage becomes more critical. A case in point in when you want a 1.5V alkaline cell to power a 1-V DSP. The alkaline cell can degrade to 1-V and the regulator can still provide power to within a few millivolts of 1 V. Dropout requirements dictate the type of pass element used and favor CMOS for very low-dropout regulators. Some regulators use a pass element and a low-loss switch that directly couples V(in) to V(out) with a small voltage drop across the switch.”
See Brian Erisman, “Voltage Regulation Tames Transients” and “Voltage Regulation Takes Trade-Offs”, ELECTRONIC ENGINEERING TIMES, at 84-100 (Oct. 4, 1999).
Note that the prior art clearly indicates that as supply voltages drop, the efficiency of the pass element becomes a significant design issue. However, little if any guidance is provided as to how to solve the problems associated with lowered supply voltages and fixed dropout voltage values in regards to high current or mixed signal integrated circuit systems.
Current Regulation
While voltage regulation and switching are the primary focus of the present invention, current and/or power regulation may be equally implemented utilizing the disclosed invention teachings in conjunction with the prior art. Current regulators, of all power variations, are detailed in the literature. See Henri J. Oguey and Daniel Aebischer, “CMOS Current Reference Without Resistance”, IEEE JOURNAL OF SOLID-STATE CIRCUITS, Vol. 32, No. 7, at 1132-1135 (Jul, 1997).
Switching Function
Additionally, in many circumstances the VCPRS module (
0102
) may be called upon to act as a high efficiency switch to completely enable or disable power dissipation by the complex load (
0103
). It is extremely important that this switching function be electrically efficient, meaning that the “on” impedance magnitude of the switch be near zero ohms. It is significant to note that it is the impedance magnitude and not just the DC resistance value of the switch that is of importance here. Thus, the parasitics associated with the voltage regulator/switch module, including parasitic “on” resistance, capacitance, and inductance are of concern in these designs, especially with highly dynamic complex loads (
0103
) as occur in a microprocessor or any analog/digital integrated circuit environment.
Multi-Value Supply Voltage Integration (
0200
)
One method employed by the prior art and which has been useful in some implementations is the use of a multi-value supply voltage topology as illustrated in FIG.
2
. Here, the system supply voltage is maintained at +5V, and used to supply both the 3.3V system regulator as well as the I/O circuitry. In this manner, the internal digital core voltages can be maintained at low voltage levels to prevent oxide punchthrough and other reliability problems, while permitting the circuit to be integrated with other +5V parts. See Gerrit W. den Besten and Bram Nauta, “Embedded 5V-to-3.3V Voltage Regulator for Supplying Digital IC's in 3.3V CMOS Technology”, IEEE JOURNAL OF SOLID STATE CIRCUITS, VOL. 33, NO. 7, at 956-962 (July 1998).
Note that any use of this technique dictates that level shifter circuitry be implemented to interface the lower internal core voltages to the higher interface voltages that are present outside the target integrated circuit. See Nobuaki Otsuka and Mark A. Horowitz, “Circuit Techniques for 1.5-V Power Supply Flash Memory”, IEEE JOURNAL OF SOLID-STATE CIRCUITS, Vol. 32, No. 8, at 1217-1230. A significant issue in all of these level shifting methodologies deals with the capabilities (or lack thereof) in the core integrated circuit fabrication process to handle the elevated voltages present outside the target integrated circuit. Thus, although a level shifting circuit suitable for the interface to the outside world can be fabricated, there still remain issues of reliability in that the higher outside voltages may stress oxides and devices in the level shifting circuitry and thus degrade the overall performance of the system.
While this technique is in general useful in designing modern integrated circuits, there still exist significant practical implementation issues in creating an efficient voltage regulat
Clark Sheila V.
Klughart Kevin Mark
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