Patent Application
20080164615
The invention relates to signal connections between an I/O region and the core region of an integrated circuit chip.
The most common layout for an integrated circuit chip provides for all power and data connections to the chip at a series of metal bonding pads arrayed in a strip adjacent the entire perimeter of the chip. Although this strip typically is rectangular, it is referred to as an “I/O region”, “I/O ring” or “pad ring” of the chip. In addition to the bonding pads, an I/O region typically includes a region radially inward of the bonding pads that includes power and ground buses in a plurality of metal layers and I/O (input/output) circuitry in semiconductor layers below the metal layers. The remainder of the chip that is encircled by an I/O region is referred to as the core.
Integrated circuit chips are designed by combining many subsystems, commonly called blocks or cells. To reduce design costs, different subsystems within a single chip commonly are designs licensed from different third parties. Subsystems licensed from third parties commonly are referred to as IP (intellectual property) cells.
Some types of subsystems require connections external to the chip. For example, a crystal oscillator subsystem requires two connections to the two pins of a crystal. As explained above, external connections typically are made at the perimeter of a chip. Therefore, subsystems that require external connections commonly are designed to be located in an I/O region so that they can connect directly to the bonding pads. Such subsystems commonly are designed to receive their operating power by direct connections to the bonding pads or to the power buses within an I/O region.
In some chip designs, it may be important for a subsystem in an I/O region to receive its operating power from circuitry in the core region of the chip rather than from the power buses or bonding pads in an I/O region. For example, to modulate power consumption by the subsystem, it may be desirable to include, in the core region of the chip a variable voltage regulator that either varies the voltage supplied to the subsystem or switches the voltage off and on. However, subsystems licensed from third parties that are designed to be located in an I/O region typically do not include a connection path for receiving power from the core; they are only designed to receive power from the power buses or bonding pads in an I/O region.
A similar problem may exist for signals other than power signals, such as analog signals or digital data signals. For example, a subsystem designed to be located in an I/O region may include a first signal connection point at which the subsystem inputs or outputs a first signal. The first signal connection point may be connected to a bonding pad in an I/O region so that the bonding pad is designed to be the only means for connecting the first signal connection point to circuitry outside the subsystem. If the subsystem does not include a connection path between the first signal connection point and the core, then a problem exists if it is desired to connect the first signal connection point to circuitry in the core.
Therefore, a need exists for a connection technique to couple operating power or any other signal between the core of a chip and a subsystem in an I/O region that does not include a connection path for such signal from the core.
The invention is an apparatus and method for connecting a signal between a first circuit within an I/O region of an integrated circuit chip and a second circuit within a core region of the chip. The first circuit is connected to a bonding pad through a first conductor in a first layer of an I/O region. The second circuit is connected to the bonding pad through a second conductor in a second layer of an I/O region above the first layer.
An advantage of the invention is that, by using a bonding pad to connect between conductors in the first and second layers, a connection can be made between the core and the first circuit even if the first circuit does not provide a direct connection path to the core.
The invention is especially valuable if a portion of the first circuit blocks a connection path between the core region and a signal connection point of the first circuit that is connected to the aforesaid first conductor. Such blockage can occur if the first circuit occupies a portion of the first layer of an I/O region between the first conductor and the core region so as to preclude a third conductor in the first layer of an I/O region from extending from the first conductor to the core region.
Numerous bonding pads are arrayed along the edge of the chip to provide signal connections to the chip. The illustrated bonding pads include pads 30-33 connected to the first circuit 12 and pads 34 connected to other circuitry (not shown) within an I/O region 10. The core region is the central region of the chip, and an I/O region is the region of the chip adjoining the bonding pads, between the bonding pads and the core.
In the illustrated embodiment, the first circuit 12 is a crystal oscillator whose connections to four bonding pads 30-33 are as follows. Pads 31 and 32 connect to an external crystal. Pad 33 connects to an electrical ground VSS. Pad 34 connects to a power supply voltage VDD.
In the exemplary integrated circuit chip, the oscillator 12 is required only during certain operational modes of the integrated circuit. During other operational modes when the oscillator is not needed, it is beneficial to either reduce or disable the supply of power to the oscillator to reduce the power consumption of the integrated circuit.
The function of enabling and disabling the supply of power to the oscillator is performed by the second circuit 22, which is a power switch or voltage regulator. The second circuit 22 includes a power input 23 at which it receives an input voltage from other circuitry in the core and a control input 24 at which it receives a control signal from other circuitry in the core. The second circuit also includes a power output 25 at which it produces an output voltage whose level is controlled by the second circuit in response to the control signal. If the second circuit is a power switch, the control signal can be a binary signal that controls whether the power switch couples the input voltage to the output 25 or sets the output voltage to zero. If the second circuit is a voltage regulator, the control signal can be an analog signal or a multi-bit digital signal that controls the level of the output voltage produced by the voltage regulator.
The oscillator circuit 12 includes a power input 14 at which it must receive its operating power. The power input of the oscillator is connected to bonding pad 30 through a conductor 16 in the first metal layer. As shown in
The conventional means of connecting to a circuit that is connected to a bonding pad is by making a direct connection to the top of the bonding pad. However, the invention takes advantage of the fact that the bonding pad extends through each of the metal layers, so a connection between the core and the bonding pad can be made by a conductor at any of these layers.
The power input 14 of the oscillator circuit 12 is in the first metal layer. Because the illustrated oscillator circuit extends into the first two metal layers, it is impractical or impossible to provide a conductor in the first layer that extends from the oscillator power input 14 to the second circuit 22 because the oscillator circuit is blocking all paths through which such a conductor could extend.
The novel means by which the power output 25 of the second circuit is connected to the power input 14 of the first circuit is a conductor 50 that connects to the power pad 30 within a metal layer above the metal layer containing the power input 14. In the illustrated example, the conductor 50 is in the fourth metal layer. A via 52 connects the conductor to the power output 25.
Although the invention has been illustrated by the example of the first circuit within an I/O region being a crystal oscillator and the second circuit within the core region being a power switch or voltage regulator, the invention is equally useful to connect any type of analog, digital, or power signal between a first circuit within an I/O region and a second circuit within the core region. Either of the two circuits can provide the signal input and the signal output, respectively. The signal input of one circuit and signal output of the other circuit can be more generally referred to as signal connection points because the invention is independent of the direction of signal flow. The invention is useful whenever it is desired to connect a signal between a first signal connection point of a first circuit within an I/O region of an integrated circuit chip and a second circuit within a core region of the chip, where the first signal connection point is connected to a bonding pad.
For the purposes of this patent description, the term “conductor” includes any connecting path formed of conductor or semiconductor material, regardless of the resistance of the connecting path or the resistivity of the material.
Various preferred embodiments and implementation features are further discussed in the following U.S. patent applications, each of which is hereby incorporated by reference in its entirety into the present patent specification:
Ser. No. 11/______ filed 31 Dec. 2006 (attorney docket SDA-1076x), entitled “Selectively Powering Data Interfaces”;
Ser. No. 11/______ filed 31 Dec. 2006 (attorney docket SDA-1076y), entitled “Selectively Powered Data Interfaces”;
Ser. No. 11/______ filed 31 Dec. 2006 (attorney docket SDA-1089x), entitled “Decoupling with Two Types of Capacitors”;
Ser. No. 11/______ filed 31 Dec. 2006 (attorney docket SDA-1089y), entitled “Chip with Two Types of Decoupling Capacitors”;
Ser. No. 11/______ filed 31 Dec. 2006 (attorney docket SDA-1090x), entitled “Internally Protecting Lines at Power Island Boundaries”;
Ser. No. 11/______ filed 31 Dec. 2006 (attorney docket SDA-1090y), entitled “Integrated Circuit with Protected Internal Isolation”;
Ser. No. 11/______ filed 31 Dec. 2006 (attorney docket SDA-1091x), entitled “Updating Delay Trim Values”;
Ser. No. 11/______ filed 31 Dec. 2006 (attorney docket SDA-1091y), entitled “Module with Delay Trim Value Updates on Power-Up”;
Ser. No. 11/______ filed 31 Dec. 2006 (attorney docket SDA-1092x), entitled “Limiting Power Island Inrush Current”;
Ser. No. 11/______ filed 31 Dec. 2006 (attorney docket SDA-1092y), entitled “Systems and Integrated Circuits with Inrush-Limited Power Islands”;
Ser. No. 11/______ filed 31 Dec. 2006 (attorney docket SDA-1093x), entitled “Programmably and Locally Detecting Power Valid”;
Ser. No. 11/______ filed 31 Dec. 2006 (attorney docket SDA-1093y), entitled “Systems and Circuits with Programmable and Localized Power-Valid Detection”;
Ser. No. 11/______ filed 31 Dec. 2006 (attorney docket SDA-1094x), entitled “Method for Performing Full Transfer Automation in a USB Controller”;
Ser. No. 11/______ filed 31 Dec. 2006 (attorney docket SDA-1094y), entitled “USB Controller with Full Transfer Automation”;
Ser. No. 11/______ filed 31 Dec. 2006 (attorney docket SDA-1095x), entitled “Method for Configuring a USB Physical Layer Interface to Loopback Mode”; and
Ser. No. 11/______ filed 31 Dec. 2006 (attorney docket SDA-1095y), entitled “Apparatus for Configuring a USB Physical Layer Interface to Loopback Mode”.
