Apple patent involves reducing voltage noise in IC device
Here's Apple's summary of the invention: "One embodiment of the present invention provides an apparatus that reduces voltage noise for an integrated circuit (IC) device. This apparatus includes an interposer, which is configured to be sandwiched between the IC device and a circuit board. This interposer has a bottom surface, which is configured to receive electrical connections for power, ground and other signals from the circuit board, and a top surface, which is configured to provide electrical connections for power, ground and the other signals to the IC device. A plurality of bypass capacitors are integrated into the interposer and are coupled between the power and ground connections for the IC device, so that the plurality of bypass capacitors reduce voltage noise between the power and ground connections for the IC device.
"The present invention reduces the voltage noise on the IC device by lowering the loop inductance the IC device sees from its ground to power pins. This is accomplished by moving the bypass capacitors closer to the IC device, which decreases the path length and also decreases the loop area and thereby decreases the loop inductance. In particular, the present invention moves the bypass capacitors from being on the side of the circuit board opposite the IC device to being located within an interposer located between the IC device and the circuit board. This reduces the inductance of the bypassing loop by eliminating the distance through the circuit board, which is a substantial portion of the bypassing inductance.
"Additionally, the present invention has the capability to greatly reduce the loop inductance (compared to a capacitor array on the opposite side of the microprocessor circuit board assembly) because it can provide more current paths (a denser array of capacitors for example) than are possible on the opposite side of the circuit board assembly. Furthermore, the volume in the interposer can accommodate more capacitance than can fit in the space on the opposite side of the circuit board."
The inventor is William P. Cornelius.
