Miscellaneous active electrical nonlinear devices – circuits – and – Signal converting – shaping – or generating – Particular stable state circuit
Reexamination Certificate
2002-11-27
2003-12-02
Wells, Kenneth B. (Department: 2816)
Miscellaneous active electrical nonlinear devices, circuits, and
Signal converting, shaping, or generating
Particular stable state circuit
C326S038000
Reexamination Certificate
active
06657470
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a method and/or architecture for implementing a programmable impedance generally and, more particularly, to a method and/or architecture for implementing a common programmable impedance pin for monolithic devices that may be used by at least two dies that each have separate programmable impedance circuitry.
BACKGROUND OF THE INVENTION
Conventional ZQ-technology provides programmable impedance for single dies. Conventional single-die ZQ-circuitry does not allow for easy expansion by multiple die techniques, such as die stacking. Connecting the ZQ pad of all the dies in a package to a single pin drives current into all the pins. The current causes deviation from the resistance value on a single die, which would typically be in the range of 5 times the required impedance. Moreover, the circuitry on each of the dies responds at different times causing the effective output impedance to change erroneously.
Referring to
FIG. 1
, a typical single-die ZQ-technology programmable impedance circuit
10
is shown. The circuit
10
illustrates a programmable impedance architecture for QDR™ SRAMs (QDR™ is a trademark of Cypress Semiconductor, Inc., San Jose, CA). The circuit
10
includes a circuit
12
and a circuit
14
. The circuit
12
has an input
16
that receives the signal ZQPAD. The circuit
12
also has an output
18
that presents the signal ZQCLK, an output
20
that presents the signal ZQLOAD and an output
22
that presents the signal ZQDATA. The circuit
14
has an input
24
that receives the signal ZQCLK, an input
26
that receives the signal ZQLOAD and an input
28
that receives the signal ZQDATA. The circuit
14
also has an output
30
that presents the signal O/P_PAD. The circuit
10
provides programmable impedance for a single die.
A designer typically chooses a resistive value to program the impedance of a die by selecting a resistor that is five times the desired impedance value. The resistor is connected between ground and the pad ZQPAD. The ZQ circuitry
12
sends out a current and measures the resulting voltage on the pad ZQPAD. Based on the result, the ZQ-circuit
12
sends three signals (ZQCLK, ZQLOAD, and ZQDATA) to the programmable output drivers
14
. Such a configuration may allow the designer to match the output impedance of the device to the transmission line impedance on a printed circuit board, resulting in improved signal integrity. The drivers
14
use the data in the ZQ-signals to set the impedance of the signal O/P PAD.
It is generally desirable to implement ZQ-technology to implement a common programmable impedance pin for multiple-die implementations within the same package.
SUMMARY OF THE INVENTION
The present invention concerns an apparatus comprising a first circuit and a second circuit. The first circuit may be configured to generate one or more first control signals in response to a reference impedance. The second circuit may be configured to operate in (i) a first mode in response to a first state of a second control signal and (ii) a second mode in response to a second state of the second control signal. When the second circuit is in the first mode, an output impedance of the second circuit may be adjusted in response to the one or more first control signals and the one or more first control signals may be presented at a first input/output of the second circuit. When the second circuit is in the second mode, the output impedance of the second circuit may be adjusted in response to one or more third control signals received at a second input/output of the second circuit.
The objects, features and advantages of the present invention include providing a method and/or architecture for implementing a common programmable impedance pin for monolithic devices that may be used by at least two dies that each have separate programmable impedance circuitry that may (i) allow many device dies to be stacked together in the same package, (ii) keep existing pin configurations constant, (iii) allow programmable output impedance for stacked dies, and/or (iv) allow ease of expansion.
REFERENCES:
patent: 6057705 (2000-05-01), Wojewoda et al.
patent: 6492853 (2002-12-01), Latham et al.
Koduru Sunil
Latham Scott
Cypress Semiconductor Corp.
Maiorana P.C. Christopher P.
Wells Kenneth B.
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