U.S. patent application number 11/197806 was filed with the patent office on 2005-12-08 for active phase cancellation for inductor/capacitor networks.
Invention is credited to Martwick, Andrew W..
Application Number | 20050270088 11/197806 |
Document ID | / |
Family ID | 34423228 |
Filed Date | 2005-12-08 |
United States Patent
Application |
20050270088 |
Kind Code |
A1 |
Martwick, Andrew W. |
December 8, 2005 |
Active phase cancellation for inductor/capacitor networks
Abstract
An apparatus and a method for active case cancellation for an
inductor/capacitor network have been presented. One embodiment of
the method includes generating a derivative of an input to a die
from a package, the derivative being out of phase relative to the
input. The method further comprises substantially canceling
resonance between an inductance of the package and a capacitance of
the die with the derivative.
Inventors: |
Martwick, Andrew W.;
(Portland, OR) |
Correspondence
Address: |
BLAKELY SOKOLOFF TAYLOR & ZAFMAN
12400 WILSHIRE BOULEVARD
SEVENTH FLOOR
LOS ANGELES
CA
90025-1030
US
|
Family ID: |
34423228 |
Appl. No.: |
11/197806 |
Filed: |
August 4, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11197806 |
Aug 4, 2005 |
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10685959 |
Oct 14, 2003 |
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6949810 |
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Current U.S.
Class: |
327/538 ;
257/E23.079; 257/E23.153 |
Current CPC
Class: |
H01L 2924/0002 20130101;
H01L 23/5286 20130101; H01L 23/50 20130101; H01L 2924/0002
20130101; H01L 2924/00 20130101 |
Class at
Publication: |
327/538 |
International
Class: |
G05F 003/02 |
Claims
What is claimed is:
1. A method comprising: generating a derivative of an input to a
die from a package, the derivative being out of phase relative to
the input; and substantially canceling resonance between an
inductance of the package and a capacitance of the die with the
derivative.
2. The method of claim 1, wherein generating the derivative
comprises driving an inductor that is substantially equal to the
inductance of the package.
3. The method of claim 1, wherein generating the derivative
comprises driving a bulk capacitor with an amplifier.
4. The method of claim 3, wherein generating the derivative further
comprises driving the amplifier with a plurality of current drawing
modules in the die, the plurality of current drawing modules being
coupled to the amplifier via a plurality of pre-emptive
resistors.
5. The method of claim 3, wherein the bulk capacitor is external to
the die and the amplifier is on the die.
Description
[0001] This Application is a divisional of application Ser. No.
10/685,959, filed Oct. 14, 2003.
FIELD OF INVENTION
[0002] The present invention relates to semiconductor circuit
design, and more particularly, to cancellation of the effect of an
input signal into an inductor/capacitor network.
BACKGROUND
[0003] In a typical semiconductor device in a computer system, a
die is mounted in a package, which is bonded through balls to a
motherboard. The connection between the package and the die has a
certain amount of inductance. On the die, there are also numerous
transistors. The die is usually coupled to a power supply, such as,
Vcc, which is fed back to the package, and then to the motherboard.
Because of this, when one or more of the transistors are turned on,
devices on the die draw current from the power supply. The net
effect is modeled by the power grid shown in FIG. 1A. The inductor
L1 represents the package inductance and the resistor R.sub.L
represents the load on the die.
[0004] Referring to FIG. 1A, when there is a change in the current
through the inductor L1, the inductance of the inductor prevents
the current from going through the inductor L1. Therefore, the
voltage across the inductor L1 drops in response to the increase in
the current draw. As the voltage drops, the current through the
inductor starts to increase. Eventually, the voltage at the node
between the inductor and the load R.sub.L would drop to the ground.
However, dropping the voltage to the ground would cause the
voltages of the components in the die to drop to the ground as
well. For example, there are flip-flops in the die using power to
store data. If the voltages of the flip-flops drop to the ground,
the data stored in the flip-flops would be lost. Furthermore,
circuits that are switching when the voltage drops to the ground
would switch incorrectly. To prevent the voltage from dropping to
the ground, an on-die capacitor C.sub.die is added to the power
grid as shown in FIG. 1B.
[0005] The on-die capacitor in FIG. 1B is initially charged to the
voltage Vcc. When the switch is initially closed, the capacitor
supplies current to the switched load RL while the current through
the inductor is increasing. This causes a drop in the voltage of
the capacitor, which is known as an undershoot. As the current
through the inductor increases to supply the current to R.sub.L, it
also supplies current to the capacitor. Thus, the current starts to
flow back into the drained capacitor to re-charge the capacitor. As
the capacitor is being charged, the capacitor voltage rises, and
subsequently, less and less current flows into the capacitor. The
excess current from the inductor flows into the load R.sub.L, and
thus, causing a rise in voltage greater than Vcc. This phenomenon
is commonly called an overshoot. The cycle of overshoot and
undershoot is commonly referred to as the ringing or the resonance.
An example of a signal having ringing is shown in FIG. 2.
[0006] Currently, the on-die capacitor is made by grounding the
substrate of a device, such as, for example, a p-type metal oxide
semiconductor transistor (pMOS), and tying the gate, the source,
and the drain of the device to a power supply, such as, Vcc. Using
current technology, the gate of the pMOS usually has a thickness of
several molecules, and therefore, current leaks through the gate.
Leakage results in increased power dissipation of the die. In
addition to the problem of leakage current, the on-die capacitor
also takes up a lot of area on the die, which increases the cost of
the device.
[0007] One prior are technique to reduce the ringing is to reduce
the inductance of the package. This allows the inductor to respond
faster to changes in the load current. The inductance of the
package is inversely proportional to the number of bonding balls on
the package. However, the bonding balls are costly as well, and
therefore, this solution is expensive.
[0008] Another prior are technique to reduce the ringing is to add
a damping resistor R.sub.d as shown in FIG. 1B. However, the
damping resistor Rd fails to reduce the undershoot and only serves
to help terminate the ringing by dissipating power.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] The present invention will be understood more fully from the
detailed description that follows and from the accompanying
drawings, which however, should not be taken to limit the appended
claims to the specific embodiments shown, but are for explanation
and understanding only.
[0010] FIG. 1A shows a power grid modeling the effect of package
inductance.
[0011] FIG. 1B shows a power grid modeling the effect of package
inductance interacting with an on-die capacitor and a damping
resistor.
[0012] FIG. 2 shows an example of a signal during ringing.
[0013] FIG. 3A shows one embodiment of an active phase cancellation
circuit.
[0014] FIG. 3B shows an example of ringing current caused by
package inductance.
[0015] FIG. 4 shows one embodiment of an active phase cancellation
circuit.
[0016] FIG. 5 shows another embodiment of an active phase
cancellation circuit.
[0017] FIG. 6 shows still another embodiment of an active phase
cancellation circuit.
[0018] FIG. 7 shows an exemplary embodiment of a computer
system.
DETAILED DESCRIPTION
[0019] In the following description, numerous specific details are
set forth. However, it is understood that embodiments of the
invention may be practiced without these specific details. In other
instances, well-known circuits, structures, and techniques have not
been shown in detail in order not to obscure the understanding of
this description.
[0020] FIG. 3A shows one embodiment of an active phase cancellation
circuit 300. The components on the left side of the circuit model
the power grid of a semiconductor die in a package, including the
power supply 301, the inductor 303, and the damping resistor 305.
Referring to FIG. 3A, the circuit further includes an on-die
capacitor C.sub.die 311, a load resistor R.sub.L 313, a second load
resistor R.sub.L.sub..sub.--2 321, an inductor L.sub.2 323, a
second capacitor C.sub.2 325, and an on-die power source 327. The
active phase cancellation circuit in FIG. 3A further includes two
switches 327 and 329. In one embodiment, the on-die power source is
twice of Vcc. In an alternate embodiment, the power source is
substantially equal to Vcc. The power source may provide different
amounts of power in other embodiments. However, the larger the
power source is, the more power is dissipated.
[0021] In one embodiment, the capacitor 325, the load resistor 321,
and the inductor 323 form an inductive-resistive-capacitive circuit
(RLC circuit) 320 substantially similar to the equivalent circuit
modeling the power grid of the die and the package. Therefore,
closing the switches 327 and 329 causes ringing in the current
flowing through the circuit 320, where the ringing is similar to
the ringing in the package but 180 degrees out of phase. In one
embodiment, the switches 327 and 329 are closed substantially
simultaneously in response to the core logic or some other current
source (not shown) of the die. The RLC circuit 320 generates a
current similar to a mirror image of the ringing current in the
package power grid. The current from the circuit 320 substantially
cancels the ringing current caused by the package inductance, and
therefore, it is unnecessary to increase the on-die capacitance or
to reduce the package inductance in order to reduce the
peak-to-peak ringing current.
[0022] FIG. 3B shows an example of a signal 391 from an exemplary
device with one embodiment of the active phase cancellation circuit
turned on and a signal 392 from the exemplary device with one
embodiment of the active phase cancellation turned off.
[0023] FIG. 4 shows an alternate embodiment of an active phase
cancellation circuit. The circuit 400 in FIG. 4 includes a bulk
capacitor 415, two inductors 411 and 413, an amplifier 417, two
feedback resistors 421 and 423, and a number of preemptive
resistors 430. Coupled to the left of the circuit 400 is a model of
the power grid 490 of a semiconductor die in a package. The power
grid 490 includes an inductor LI 491 representing the package
inductance, a capacitor C.sub.die 493 representing the die
capacitance, and a resistor R.sub.L representing the load
resistance. In one embodiment, the capacitance of the bulk
capacitor 415 is 300 pF and the capacitance of C.sub.die 493 is 30
nF. However, one should appreciate that these capacitance values
are provided herein merely as examples. Other embodiments include
capacitors of different values.
[0024] In one embodiment, the preemptive resistors 430 coupled a
number of current-drawing modules (not shown) in the core logic of
the die to a first input of the amplifier 417. The output of the
amplifier 417 drives the inductors 411 and 413 and the bulk
capacitor 415. The inductors 411 and 413 and the bulk capacitor 415
are coupled to each other in series. The feedback resistors 421 and
423 couple a second input of the amplifier 417 to each end of the
series of the inductors 411 and 413 and the bulk capacitor 415. A
feedback of the voltage across the inductors 411 and 413 and the
bulk capacitor 416 may be provided to the amplifier 417 via the
feedback resistors 421 and 423. In one embodiment, the bulk
capacitor 415 is initially charged to store resonance energy. When
ringing occurs in the power grid 490, the amplifier 417 drives the
resonance energy out of the bulk capacitor 415 onto the power grid
490 to generate a signal to substantially cancel the ringing signal
in the power grid 490.
[0025] In one embodiment, the amplifier 417 is capable of driving
the transient current of the load resistor R.sub.L 495. The
transient current may go up to 1A in an exemplary chipset device.
In one embodiment, the bulk capacitor 415 is off-die, and the other
components are on-die. In an alternate embodiment, the bulk
capacitor 415 is on-die with other components of the circuit 400.
Using off-die capacitor reduces the cost of the die because of the
saving in the silicon area of the die.
[0026] In one embodiment, the equivalent inductance of the
inductors 411 and 413 substantially matches the package inductance
L1 491 in the power grid 490. In one embodiment, the inductors 411
and 413 have substantially the same inductance. In an alternate
embodiment, a single inductor, instead of two inductors, is coupled
to the bulk capacitor 415.
[0027] FIG. 5 shows an alternate embodiment of an active phase
cancellation circuit in an exemplary device. Referring to FIG. 5,
the active phase cancellation circuit 500 includes a number of
preemptive resistors 530, an amplifier 517, a bulk capacitor C_bulk
515, and two feedback resistors 521 and 523. A circuit 590 modeling
the power grid of the die in the package is coupled to the active
phase cancellation circuit 500. The power grid 590 includes a power
source Vcc 597, an inductor L1 591 representing the package
inductance, a capacitor C.sub.die 593 representing the on-die
capacitance, and a resistor 595 representing the load of the
die.
[0028] In one embodiment, the preemptive resistors 530 coupled a
number of current drawing modules in the core logic (not shown) of
the die to the positive input terminal of the amplifier 517. In one
embodiment, the output terminal of the amplifier 517 is coupled to
the base of the bulk capacitor 515. The other end of the bulk
capacitor 515 is coupled to the circuit 590. In one embodiment,
each end of the bulk capacitor 515 is also coupled via one of the
two feedback resistors 521 and 523 to the negative input terminal
of the amplifier 517 to provide a feedback to the amplifier.
[0029] In one embodiment, the step response of R.sub.L 595 is
canceled by the derivative response of an impulse function through
the bulk capacitor 515. This impulse response of opposite polarity
is driven onto the circuit 590 at the same time as the step
response of R.sub.L 595. The derivative response then serves to
cancel the change in voltage across the inductor, since the
derivative of the step response is a delta function. It can be
shown that any input into the network, such as the step response
represented by the closing of the switch, can be canceled by
driving the derivative of the input signal through the bulk
capacitor 515, such as the delta function, which is a derivative of
the step response.
[0030] FIG. 6 shows an alternate embodiment of an active phase
cancellation circuit. The circuit in FIG. 6 includes a number of
modules 610-630, each being substantially similar to the active
phase cancellation circuit 500 shown in FIG. 5. For example, the
module 610 includes a number of preemptive resistors 611, an
amplifier 612, two feedback resistors 613 and 614, and a bulk
capacitor 615. In one embodiment, there are 3 modules in the active
phase cancellation circuit. In other embodiments, there are
different numbers of modules, such as, for example, 2, 5, etc.
[0031] Referring to FIG. 6, the bulk capacitance used to generate a
current to substantially cancel the ringing current caused by
package inductance is broken down and distributed into a number of
smaller capacitors, one in each of the modules 610-630, such as,
for example, the bulk capacitor 615 in module 610. In one
embodiment, an amplifier in each module drives the corresponding
bulk capacitor. For example, the amplifier 612 in module 610 drives
the bulk capacitor 615. In one embodiment, the amplifier 612 in the
module 610 has a gain smaller than the gain of the amplifier 517
shown in FIG. 5 because the bulk capacitor 615 in the module 610 is
smaller than the bulk capacitor 515 in FIG. 5. Likewise, each of
the amplifiers in the modules 620 and 630 has a smaller gain than
the amplifier 517 in FIG. 5. In one embodiment, the amplifiers in
the modules 610-630 have substantially the same gain.
[0032] FIG. 7 is a block diagram of an exemplary embodiment of a
computer system. The system 700 includes a central processing unit
(CPU) 701, a memory controller (MCH) 702, an input/output
controller (ICH) 703, a flash memory device storing the Basic Input
Output System (Flash BIOS) 704, a memory device 705, a graphics
chip 706, and a number of peripheral components 710. The CPU 701 is
coupled to the MCH 702 via a front side bus (FSB) 712. The CPU 701
includes a microprocessor, but is not limited to a microprocessor,
such as, for example, Pentium.RTM. processor, Itanium.RTM.
processor, PowerPC.RTM., etc. The memory device 705, the graphics
chip 706, and the ICH 703 are coupled to the MCH 702. The memory
device 705 may include a dynamic random access memory (DRAM), a
Rambus.RTM. dynamic random access memory (RDRAM), or a synchronous
dynamic random access memory (SDRAM).
[0033] In one embodiment, data sent and received between the CPU
701, the memory device 705, the graphics chip 706, and the ICH 703
are routed through the MCH 702. The peripheral components 710 and
the flash BIOS 704 are coupled to the ICH 703. The peripheral
components 710 and the flash BIOS 704 communicate with the CPU 701,
the graphics chip 706, and the memory 705 through the ICH 703 and
the MCH 702. Note that any or all of the components of system 700
and associated hardware may be used in various embodiments of the
present invention. However, it can be appreciated that other
configurations of the computer system may include some or all of
the devices.
[0034] Due to the package inductance of various packaged
semiconductor devices in the computer system 700, there is ringing
of signals in the devices and the buses coupling the devices, such
as, for example, the MCH 702, the CPU 701, the FSB 712, etc.
Ringing may also be referred to as resonance.
[0035] To reduce ringing, one or more of the devices in the system
700 may incorporate an active phase cancellation circuit to reduce
ringing by generating a signal to substantially cancel the ringing
signal caused by the package inductance. In one embodiment, the FSB
712 includes an active phase cancellation circuit 723. In one
embodiment, the CPU 701 includes an active phase cancellation
circuit 721 to reduce ringing. The active phase cancellation
circuit 721 may be integrated into the input/output (I/O) of the
CPU 721. In one embodiment, the MCH 702 includes an active phase
cancellation circuit 722 to reduce ringing as well.
[0036] In one embodiment, the active phase cancellation circuit
includes a capacitor, an inductor, and a resistor coupled in series
to an on-die power source to generate a current to substantially
cancel the ringing signal caused by the package inductance. In an
alternate embodiment, the active phase cancellation circuit
includes an amplifier, a number of preemptive resistors, and a bulk
capacitor. The preemptive resistors couple a number of current
drawing modules in the core logic of the die to the amplifier so
that the amplifier can drive the bulk capacitor to generate a
current to substantially cancel the current caused by ringing.
[0037] The foregoing discussion merely describes some exemplary
embodiments of the present invention. One skilled in the art will
readily recognize from such discussion, the accompanying drawings
and the claims that various modifications can be made without
departing from the spirit and scope of the appended claims. The
description is thus to be regarded as illustrative instead of
limiting.
* * * * *