Electricity: power supply or regulation systems – Output level responsive – Using a three or more terminal semiconductive device as the...
Reexamination Certificate
1999-12-08
2001-01-09
Wong, Peter S. (Department: 2838)
Electricity: power supply or regulation systems
Output level responsive
Using a three or more terminal semiconductive device as the...
C323S269000, C323S274000
Reexamination Certificate
active
06172490
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to integrated circuits having dual supply voltage requirements and, more particularly, to a system and method for accurately controlling the dual supply voltage levels.
BACKGROUND OF THE INVENTION
Many large scale integrated circuits contain multiple components providing different functionality and require two different supply voltage levels to operate. One such integrated circuit would include, for example, a core processor and input/output functions on the same silicon substrate, but operating from two different voltage levels. During startup, steady state, shut down and under fault conditions, the interaction between these voltages must meet strict requirements to ensure proper operation and to prevent damage to the integrated circuit. The techniques used to ensure proper interaction of these voltage levels all fall under the class of methods known as “Rail Tracking”.
In a dual supply voltage mode scenario, typically, the larger of the two voltage rails will supply the input/output function, and the smaller of the two is used to power the core processor. The larger of the two voltage levels is supplied to the input/output functionality of the integrated circuit, and to a voltage regulator which derives the second or lower voltage level for use in powering the core processor.
The task of the voltage regulator consists of keeping the voltage on the output constant in a defined output range. One form of voltage regulator comprises a switch mode power supply. A switch mode power supply usually comprises a pulse width modulator (PWM), a power switch, a rectifier and an output filter. The pulse width modulator controls the power switch which converts an input voltage into pulsed DC voltage with variable duty cycle which in effect maintains constant voltage on the output of the filter circuit. In conventional voltage regulator voltage to power the PWM circuit is derived from the regulator's input voltage.
Because the PWM circuit requires a finite period to achieve steady state conditions there is an initial period between the time that the voltage is supplied to the regulator input and the time in which the output is fixed at the second voltage level. During this time the voltage difference between the input/output voltage and output core voltage may exceed maximum allowable limits causing damage to the integrated circuit.
A prior art method dealing with this problem is disclosed in Power Trends application note PT5000/6000 SIP Series (Integrated Switching Regulators DC—DC Converters). In this prior art solution, the voltage regulator is bypassed by a number of series connected diodes and a small resistor which are connected between the input/output voltage level and the core processor voltage. The series-connected diodes limit the difference between the two voltage levels as will be discussed in greater detail hereinafter.
There are shortcomings to this prior art method which render it unacceptable in certain circumstances. For example, as the steady state difference between the input/output voltage and the core processor voltage approaches the maximum allowable voltage difference, the tolerance on the diode voltage drop becomes critical. This tolerance is difficult to control inasmuch as the voltage drop across the diode junction is highly current and temperature dependent. Additionally, the tracking voltage difference can be set only with the resolution of each single junction voltage drop which typically equals approximately 0.6 volts or 0.3 volts for Schottky technology. Additionally, the series-connected diodes bypassing the voltage regulator negate any overcurrent protection provided by the voltage regulator. In addition, the diodes themselves can be easily damaged if the regulator fails as all of the current associated with the second voltage level will now flow through the diodes.
SUMMARY OF THE INVENTION
Accordingly, there is a requirement for an improved rail tracking system and method for powering a dual voltage integrated circuit.
Therefore, in accordance with a first aspect of the present invention there is provided a rail tracking method for providing dual voltages levels to first and second voltage rails on an integrated circuit (IC) comprising: providing a first voltage to the first voltage rail; providing the first voltage to a voltage regulator having conversion means to derive a second voltage for the second voltage rail; and providing a supply voltage to the conversion means whereby the supply voltage is provided before the first voltage is provided to the voltage regulator.
In accordance with a second aspect of the present invention there is provided a system for providing rail tracking of dual voltage levels to first and second voltage rails on an integrated circuit comprising: first voltage means to supply a first voltage level to the first voltage rail; a voltage regulator having means to receive the first voltage level; conversion means in the voltage regulator to derive a second voltage level for the second voltage rail from the first voltage level; and a supply voltage means to supply a supply voltage to the conversion means wherein the supply voltage is supplied to the conversion means before the first voltage is supplied to the voltage regulator.
REFERENCES:
patent: 4087759 (1978-05-01), Iwamatsu
patent: 4472687 (1984-09-01), Kashiwagi et al.
patent: 5200711 (1993-04-01), Anderson et al.
patent: 5543753 (1996-08-01), Williamson
patent: 5606289 (1997-02-01), Williamson
patent: 5898340 (1999-04-01), Chatterjee et al.
patent: 6011382 (2000-01-01), Littlefield et al.
Power Trends, Inc. application note entitled: “Integrated Switching Regulators, DC to DC Converters”.
(Marks & Clerk)
Alcatel Networks Corporation
Vu Bao Q.
Wong Peter S.
LandOfFree
Precise rail tracking method for powering dual voltage... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Precise rail tracking method for powering dual voltage..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Precise rail tracking method for powering dual voltage... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2498375