Electrical computers and digital data processing systems: input/ – Intrasystem connection – Bus access regulation
Reexamination Certificate
1999-03-30
2001-12-04
Dharia, Rupal (Department: 2181)
Electrical computers and digital data processing systems: input/
Intrasystem connection
Bus access regulation
C710S108000, C710S108000, C710S002000, C713S300000, C713S340000, C365S226000, C365S229000
Reexamination Certificate
active
06327635
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to computer systems. More particularly, the present invention relates to voltage supply circuits for add-on cards in PCs and other computer systems.
2. Brief Description of the Related Art
Personal Computers (PCs) and other types of computer systems commonly include expansion slots for receiving add-on cards. The expansion slots are typically provided on the host computer's motherboard, and provide access to signal lines of the computer's main bus. Any of a variety of different types of cards can be added to the computer system using the expansion slots, including host adapter boards, network cards, and hardware accelerators.
The add-on cards receive power from the host computer's power supply using power supply lines of the main bus. In computers that use a Peripheral Component Interconnect (PCI) type bus, these power supply lines have traditionally provided a voltage level of 5V. Recently, however, there has been a trend in the industry towards using 3.3V components that consume less power. As a result, manufacturers of PC systems sometimes provide a PCI bus that includes an additional, 3.3V power supply line. When this extra voltage supply level is provided, both 3.3V and 5V type cards can be used within the system.
Unfortunately, because not all PCs are provided with a 3.3V power level, add-on cards are commonly designed to use only the 5V supply, and to step down to 3.3V internally. This step-down method causes the cards to consume more system power than is necessary. In addition, the provision of such cards impedes the ability of PC manufacturers to eventually eliminate the 5V supply, as is desirable for reducing manufacturing costs. The elimination of the 5V supply also has the effect of reducing the cost of power supplies since only a single voltage level is provided.
SUMMARY OF THE INVENTION
An add-on card for a computer bus that automatically selects the low voltage line available on a bus is provided. The add-on card includes a voltage selection circuit that detects the presence of a low voltage and uses that voltage to supply power to the add-on card. The voltage selection circuit includes a detector for every voltage level that may be supplied on a bus. The voltage selection circuit is constructed such that a voltage regulator for a given voltage level is automatically disabled by a detection of any voltage lower than that voltage but higher than a minimum voltage required for proper operation of the add-on card.
The add-on card is preferably used within a computer system having an expansion slot connected to a bus. The bus has a first supply line for supplying a first predetermined voltage and a second supply line for supplying a second predetermined voltage which is higher than the first predetermined voltage. The add-on card is adapted to operate properly regardless of whether the respective predetermined voltages are supplied on (1) the first supply line only, (2) the second supply line only, or (3) both supply lines. The add-on card includes a selection circuit which connects to the first and second supply lines. The selection circuit detects the presence of the first predetermined voltage on the first supply line and selects between the first and second supply lines as a power source for at least one integrated circuit of the card. The selection circuit selects the first supply line as the power source when the detection circuit detects the first predetermined voltage on the first power supply line. A step-down circuit steps down a voltage provided on the second supply line when the second power supply line is selected as the power source. In a 5V/3.3V PCI embodiment, the card operates in the following supply voltage configurations: 5V only, 3.3V only, and 5V/3.3V.
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Alston Jerald K.
Craven Mark L.
Tran Henry
Dharia Rupal
Knobbe Martens Olson & Bear LLP
QLogic Corporation
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