Patent Application
20050045987
1. Field of the Invention
This invention generally relates to integrated circuits, and more particularly to an integrated circuit package having an inductance loop formed from at least one input/output pin of the package.
2. Description of the Related Art
One perennial goal among circuit designers is to decrease the size of integrated circuits. This goal is largely driven by market demand for ever-smaller consumer electronics, communications devices, and display systems to mention a few. There are, however, a number of impediments that undermine this goal, one of which will now be discussed.
Many integrated circuits are not self-contained devices. To ensure proper operation, these circuits must therefore be connected to one or more external components through connections which do not involve the use of an IC package input/output pin. This is accomplished, for example, by connecting the integrated circuit chip 1 to an off-package component 2 using bonding wires 3, as shown in
One conventional integrated circuit requiring off-package connections is routinely used in the frequency synthesizer of mobile communications devices such as cellular phones. Because the phase noise specifications are so stringent in these devices, voltage-controlled oscillators in a phase-locked loop used to generate the frequencies are typically based on some resonant structure. Ceramic resonators and LC tank circuits are common examples. While details in the implementation of LC tank oscillators differ, the general resonant structure includes an inductor connected in parallel with a fixed capacitor (C) and a variable capacitor (Cx). In the absence of any losses, energy passes between the capacitors and the inductor at a frequency fout=(½π) [L(C+Cx)]−1/2, with the inductance value L selected to control the operating band of the device.
In an integrated circuit which includes the aforementioned frequency synthesizer, the inductor used for band-selection purposes is located off-package (i.e., is circuit-board mounted). The use of off-package or board-mounted inductors increases system costs. Moreover, connection problems may occur between the package and board which may adversely affect the reliability and performance of the PLL circuitry.
Attempts have been made to overcome the drawbacks of these conventional devices. One approach, disclosed in U.S. Pat. No. 6,323,735, forms an inductor entirely within the integrated circuit package containing the phase-locked loop circuitry. This is accomplished using conductive wires which connect bonding pads on the IC chip to a same bonding pad on the package substrate. The connection between the pads and wires forms an inductance loop which controls the operational frequency band of the PLL circuitry. Multiple bonding pads may be included on the package substrate to form inductor loops of varying length. The loops are then selectively activated to effect a change in operational frequency.
The approach taken in the '735 patent is undesirable for at least two reasons. First, in order to form the inductor loop completely within the IC package, the package substrate must be formed to include bonding pads separate from the input/output package pins. The need to form these special pads increases the cost and complexity of the manufacturing process. Second, in order to accommodate the bonding pads, the size of the integrated circuit substrate must be increased and as a result more circuit board space is consumed. These effects undermine the goal of increasing integration and miniaturization.
Another approach, disclosed in the text “Wireless CMOS Frequency Synthesizer Design,” by Craninckx, discloses a self-contained integrated circuit package containing an inductor loop. This loop is formed by connecting bonding wires between bonding pads on the IC chip and respective input/output pins of the IC package. The input/output pins are then connected by a third bonding wire. While this approach does not require the formation of special bonding pads on the package substrate, it is has at least two drawbacks that make it undesirable. First, like in the '735 patent, a bonding wire is used to connect the input/output pins. As previously noted, these wires are susceptible to damage during manufacture and/or use. Second, the input/output pins connected by the third bonding wire are located on opposite sides of the package. As a result, the third wire must pass over the IC chip. This is undesirable because the wire could short certain portions of the chip circuitry and introduce noise and other interfering influences which substantially degrade chip performance.
In view of the foregoing considerations, it is apparent that a need exists for an integrated circuit package which is more economical and requires fewer processing steps to manufacture than conventional IC packages, and which is also less susceptible to damage and noise which can degrade reliability and performance not only of the chip circuitry but also the host system of the chip. A need also exists for an integrated circuit package which is self-contained at least with respect to connection of an inductor loop connected to the chip, and which is able through this connection to achieve at least one of the aforementioned advantages.
An object of the present invention is to provide an integrated circuit package which is more economical and requires fewer processing steps to manufacture than conventional IC packages.
Another object of the present invention is to provide an integrated circuit package which is less susceptible to damage and noise which can degrade reliability and performance not only of the chip circuitry but also of the host system of the chip.
Another object of the present invention is to provide an integrated circuit package which is self-contained at least with respect to connection of an inductor loop to the IC chip and which is able through this connection to achieve at least one of the aforementioned advantages.
Another object of at least one embodiment of the present invention is to accomplish one or more of the aforementioned objects by reducing the number of bonding wires used to form the inductor loop compared with the number of wires used in conventional self-contained integrated circuits.
Another object of the present invention is to provide an integrated circuit package which does not require special bonding pads to be formed on the package substrate in order to form an inductor loop connected to the chip.
Another object of the present invention is to achieve one or more of the aforementioned objects by forming the inductor loop from at least one input/output pin of the package.
These and other objects and advantages of the present invention are achieved by providing a semiconductor package comprising an integrated circuit chip and an inductor loop which is connected in a self-contained manner within the package. This self-contained connection is accomplished by forming the loop from at least two conductors. The first conductor connects a bonding pad on the chip to an input/output pin of the package. The second conductor connects the same bonding pad on the chip to the same input/output pin of the package, thereby forming a loop. At least a third conductor may be added between the same pin and pad to increase the effective length of the inductor to thereby achieve a desired inductance. The conductors are preferably bonding wires.
In accordance with another embodiment, the semiconductor package comprises an integrated circuit chip and an inductor loop which is connected in a self-contained manner within the package. This inductor loop is formed from a plurality of sub-loops. The first sub-loop includes a first conductor which connects a bonding pad on the chip to an input/output pin of the package and a second conductor which connects the same bonding pad to the same pin. The second sub-loop includes one of the first and second conductors and a third conductor connected between the pin and pad. The conductors are preferably bonding wires.
The present invention is also an oscillator circuit which includes an active oscillator having two output nodes, an inductor loop coupled to the output nodes, and at least one capacitive circuit coupled to one of the output nodes. The capacitive circuit includes a capacitor, a resistor, and a first switch and the resistor provides a bias voltage to the capacitor when the first switch is open. The first switch couples and decouples the capacitor to the output nodes of the active oscillator. Preferably, the active oscillator and capacitive circuit are included in a semiconductor package which includes an integrated circuit chip. When configured in this manner, the inductor loop includes a first conductor connecting a bonding pad on the chip to an input/output pin of the package and a second conductor connecting the bonding pad on the chip to the input/output pin of the package. The first and second conductors may be bonding wires and the inductor loop may include at least a third conductor connecting the bonding pad on the chip to the input/output pin of the package.
In accordance with another embodiment, the present invention provides an oscillator circuit as previously described but with a different inductor loop configuration. This inductor loop includes has two sub-loops, the first of which includes a first conductor connecting a bonding pad on the chip to an input/output pin of the package and second conductor connecting the bonding pad on the chip to the input/output pin of the package. The second sub-loop includes one of the first conductor and the second conductor and a third conductor connecting the bonding pad on the chip to the input/output pin of the package. The first conductor and the second conductor are bonding wires.
The present invention is, in one respect, a semiconductor package having an integrated circuit chip and an inductor loop which is connected in a self-contained manner within the package. The present invention is also a system which is at least partially controlled by the inductor loop of the semiconductor device mentioned above. The system may be a communications system where the inductor loop is used to set a transmitter and/or RF carrier frequency or another type of system. The various embodiments of the invention will now be discussed in seriatim below.
The I/O pins may take any one of a variety of forms. For example, the pins are shown as external package leads disposed along a periphery of the package substrate. However, if desired the pins may be formed in other ways including but not limited to electrically conductive vias which extend through the package substrate to solder bump connections provided on an opposing side of the package.
The semiconductor package also includes an inductor loop 20 self-contained within the package. The inductor loop may be formed from two conductors. The first conductor 22 connects a first bonding pad 24 on the chip to a first input/output pin 26 of the package, and the second conductor 23 connects the same bonding pad to the same input/output pin. In this embodiment, the pin connects the two conductors to thereby complete the loop. The first and second conductors are preferably bonding wires.
Once the inductor loop is formed, it may be used to control one or more circuits on the integrated circuit chip. For example, if the integrated circuit includes a phase-locked loop, the inductance value of the loop may be used to set an output frequency or frequency band of this circuit. Alternatively, the length of the loop may be used to set other operational parameters of the chip. The inductance value of the loop depends on its overall length. This length may be set in various ways to achieve the desired inductance value. For example, the length of the first and second conductors may be set to have specific lengths based on a loop length to be achieved. The specific application of the inductor loop of the present invention may be adapted, for example, depending upon the parameters being set and the specific function to be performed by the integrated circuit.
The semiconductor package also includes an inductor loop 120 self-contained within the package. The inductor loop is formed from two sub-loops. The first sub-loop is formed by connecting a first conductor 122 between a bonding pad 124 on the chip and a first input/output pin 126 of the package and a second conductor 133 between the same bonding pad and package pin. The second sub-loop is formed by one of the first and second conductors and at least a third conductor 23 connected between the same pad and pin. The conductors are preferably bonding wires. The inductor loop therefore has an effective length (and thus an inductance value) based on the sum of the two sub-loops. Those skilled in the art can appreciate that additional conductors may be added between the pad and pin to increase the number of sub-loops comprising the inductor.
A semiconductor package in accordance with any of the aforementioned embodiments may be used in any one of a variety of applications. One exemplary application is in a communication system where the inductor loop is used to set one or more parameters such as but not limited to an operating frequency. One illustrative embodiment of a voltage-controlled oscillator which may be included in such a communication system will now be described.
Other modifications and variations to the invention will be apparent to those skilled in the art from the foregoing disclosure. Thus, while only certain embodiments of the invention have been specifically described herein, it will be apparent that numerous modifications may be made thereto without departing from the spirit and scope of the invention.
| Number | Date | Country | |
|---|---|---|---|
| 60498353 | Aug 2003 | US |
