Miscellaneous active electrical nonlinear devices – circuits – and – Signal converting – shaping – or generating – Amplitude control
Reexamination Certificate
1999-12-14
2001-08-07
Cunningham, Terry D. (Department: 2816)
Miscellaneous active electrical nonlinear devices, circuits, and
Signal converting, shaping, or generating
Amplitude control
C327S310000, C327S551000
Reexamination Certificate
active
06271704
ABSTRACT:
FIELD
This invention relates to termination devices, and more specifically to balancing current in a system with termination devices connected to different power sources.
BACKGROUND
Due to the rapid advance of technology, many times electronic systems and devices become outdated in a short amount of time. In these cases, a person may buy a new electronic system, and no longer have a use for the original system. One way to salvage the original electronic system is to determine if it can be modified to make it perform like the new electronic system. If this may be accomplished by only exchanging a few electronic components, this may be a much simpler and less costly process than a new system. The problem arises if the new electronic component when inserted into the same location as an original electronic component, has the potential to cause problems in the electronic system even though the interconnections are the same.
FIG. 1
shows a schematic diagram of an example circuit in an existing electronic system with an IC (Integrated Circuit)
2
that includes a die
4
on a package
6
. IC
2
attaches to a motherboard
8
through socket
10
. Vcc voltage regulator
12
supplies Vcc voltage to the core circuits in IC
2
. Vtt voltage regulator
14
supplies voltage to termination devices
16
that is connected to IC
2
GTL (Gunning Transceiver Logic) signal line
18
. Therefore, GTL signal line
18
has a termination device connected to it that is mounted on motherboard
8
. Although
FIG. 1
shows only one signal line, this is representative of all GTL or open drain type signal lines of IC
2
that connect to other devices on motherboard
8
. There may also be open drain signal lines that are not GTL signal lines. These signal lines may be capable of using a higher termination voltage than the GTL signal lines. For this reason, IC
2
may receive voltages from the Vcc voltage and the Vtt voltage and depending on the devices attached to the non-GTL signal lines, supply a non-GTL signal line termination voltage
20
, that is either the Vcc voltage or the Vtt voltage, to the termination devices attached to non-GTL signals (e.g., CMOS signals).
If a person desires to upgrade the electronic system shown in
FIG. 1
for improved performance and/or functionality, IC
2
might need to be replaced with another improved IC. The improved IC must be electrically compatible with IC
2
in order to be attached to motherboard
8
. A problem may arise when the improved IC is compatible with IC
2
, but has termination devices on the die of the improved IC. That is, when the improved IC is attached to motherboard
8
, the GTL signal lines now have termination on the motherboard, and termination on the die of the improved IC and such termination resistors may cause a conflict or degradation in an operation of the circuit.
As description of one example problem, an improved IC with termination on the die (not shown) will likely have the on die termination connected between the Vcc voltage from voltage regulator
12
and GTL signal line
18
. As the number of IC
2
GTL signal lines
18
that are not pulled down to ground increases, the current flow from Vcc voltage regulator
12
to Vtt voltage regulator
14
may increase. Generally, most voltage regulators require a minimum amount of current to be sourced by the regulator for the voltage regulator to stay within the proper voltage regulation range. If most or all of the signals from IC
2
are pulled up through the termination devices, enough current may flow from Vcc voltage regulator
12
to Vtt voltage regulator
14
through the termination devices such that the minimum regulation current requirement for Vtt voltage regulator
14
is not met and, therefore, voltage regulator
14
shuts down. This may cause system problems, for example, unacceptable noise signal levels within the system.
A solution to this problem is to remove the current path between the voltage regulators. However, removing the current path may not be an option due to the fact that the design of already existing motherboards cannot be easily changed in the field and the need for on die termination with the new ICs. The motherboards have already been designed and currently may exist with termination on the motherboard. Therefore, the motherboard would need to be reworked when an IC with on die termination is inserted.
A further possible solution is to set the voltage regulators to voltages that will not cause current flow from the Vcc voltage regulator to the Vtt voltage regulator. However, setting both voltage regulators to voltages that will not cause current flow would likely require the Vcc voltage regulator to be set lower and possibly not allow for optimum IC performance (e.g., raising the Vcc voltage generally results in improved IC performance).
Therefore, a need exists for an arrangement allowing a semiconductor IC device with termination on the die that can be substituted for a semiconductor IC device with termination not on the die attached to an existing motherboard of an electronic system, and not have any potential for voltage regulators shutting off and causing system problems.
SUMMARY
A current dump circuit that includes a current dump device provided on an on-die or on-package peripheral attached to a system. The current dump device may be adapted to allow a predetermined minimum of current to flow from a voltage regulator so as to keep the voltage regulator operating within a predetermined operating range.
REFERENCES:
patent: 5604450 (1997-02-01), Borkar et al.
patent: 5729154 (1998-03-01), Taguchi et al.
patent: 6008682 (1999-12-01), Mirov
patent: 6064507 (2000-05-01), Heflinger et al.
patent: 6114898 (2000-09-01), Okayasu
Babcock Sean R.
Sarangi Ananda
Antonelli Terry Stout & Kraus LLP
Cunningham Terry D.
Intel Corporation
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