Static information storage and retrieval – Read/write circuit – Flip-flop used for sensing
Reexamination Certificate
2000-12-20
2001-11-13
Le, Vu A. (Department: 2824)
Static information storage and retrieval
Read/write circuit
Flip-flop used for sensing
C365S207000
Reexamination Certificate
active
06317374
ABSTRACT:
BACKGROUND OF THE INVENTION
Field of the Invention
The invention relates to a method for operating a current sense amplifier having a latch configuration. A supply voltage is applied to the latch configuration. Transistors of the latch configuration are connected to one another via nodes and are connected to precharge transistors. The current sense amplifier has sense transistors which are connected downstream of an input and are provided between the latch configuration and an output stage. The precharge transistors are provided between the input and the supply voltage and are controlled via the nodes.
Such a current sense amplifier is conventional and has been in widespread use for a long time. The signal-to-noise ratio of such a current sense amplifier is in many cases still unsatisfactory which can be attributed to technological problems during the production of the current sense amplifier.
Specifically, as a result of technological process fluctuations, the nodes in the current sense amplifier may have different capacitances. This means that the nodes can discharge themselves even when identical voltages are present at them. This parasitic discharging process is dependent on the gate voltage applied to the sense transistors. In other words, there are voltage ranges in which the signal-to-noise ratio of the current sense amplifier drifts into unsatisfactory ranges.
In-order to overcome these difficulties, a relatively long waiting time has been used in the past to ensure that the signals applied to the gates of the sense transistors have been built up or developed sufficiently before actually switching the current sense amplifier on. It has also been suggested to use slower operating sense concepts. However, these approaches have been found to be cumbersome.
SUMMARY OF THE INVENTION
It is accordingly an object of the invention to provide a method for operating a current sense amplifier configuration which overcomes the above-mentioned disadvantages of the heretofore-known methods of this general type and which improves the signal-to-noise ratio in a simple manner.
With the foregoing and other objects in view there is provided, in accordance with the invention, a method for operating a current sense amplifier configuration, the method includes the steps of:
providing a current sense amplifier having an input, a latch configuration, precharge transistors, sense transistors, and an output stage, the latch configuration having transistors connected to one another via nodes and connected to the precharge transistors, the sense transistors being connected downstream of the input and being connected between the latch configuration and the output stage, the precharge transistors being controlled via the nodes and being connected between the input and a supply voltage;
providing the supply voltage to the latch configuration; and
providing a given voltage at the input, the given voltage having a value at most equal to a difference between the supply voltage and a threshold voltage or switch-on voltage of p-channel MOS transistors of the latch configuration.
In other words, the object of the invention is achieved by setting the voltage which is present at the input to be lower than the supply voltage.
Thus, in the method according to the invention, the voltage which is applied to the gates of the sense transistors is never greater than the supply voltage for the latch configuration. The voltage which is present at the input is, optimally, not greater than the difference between the supply voltage and the threshold voltage of p-channel transistors in the latch configuration.
The method according to the invention thus allows a selection of the optimum voltages for supplying the latch configuration and the input of the sense transistors, so that a sense process can be carried out extremely quickly.
The voltage which is present at the input and the supply voltage for the latch configuration can advantageously be set separately from one another.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in a method for operating a current sense amplifier, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
REFERENCES:
patent: 5491667 (1996-02-01), Sharp
patent: 5502680 (1996-03-01), Du et al.
patent: 5615161 (1997-03-01), Mu
patent: 5883846 (1999-03-01), Lee
patent: 6002626 (1999-12-01), Lattimore et al.
Greenberg Laurence A.
Infineon - Technologies AG
Le Vu A.
Lerner Herbert L.
Stemer Werner H.
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