Sun Microsystems, Inc.

Oracle America, Inc.

Montalvo Systems, Inc.

Ajay Bhatia

Dennis L Wendell

Jun Liu

Yolin Lih

Daniel Fung

Shyam Sundar Balasubramanian

Shashank Shastry

Sanjay M Wanzakhade

Rajesh Khanna

Sagar V Reddy

Uttam Saha

Shyam Balasubramanian

A memory device having a split power switch is provided to improve the writeability of static random access memory (SRAM) cells without adversely compromising their stability. For example, various split power switch circuits are used to permit the voltage or current of a power supply line connected with one side of an SRAM cell to drop during write operations. This drop weakens one side of the SRAM cell and reduces the drive-fight between transistors of the SRAM cell and external write circuitry. As a result, the minimum voltage for writing new logic states into the SRAM cell is reduced to permit overall lower operating voltages for the SRAM cell and related circuitry. By continuing to maintain a second side of the SRAM cell at the reference voltage or current, the SRAM cell can successfully switch to a newly written logic state.

Memory device with split power switch

Static random access memory (SRAM) cells and methods of operation are provided which may be used to provide improved writeability and stability to support low voltage operation of memory devices. For example, in one implementation, by temporarily interrupting the connection between portions of an SRAM cell and a power source such as a reference voltage or current source, the writeability of SRAM cells can be improved. Additional read port implementations are also provided to facilitate low voltage operation. In another implementation, a power switch circuit responsive to a word line and logic signals may be used to provide such interruptions.

Memory cells with power switch circuit for improved low voltage operation

An elastic power header device and methods of operation are provided to improve the read margin of static random access memory (SRAM) cells by increasing read stability, reducing read disturbance and improving the Signal to Noise Margin (SNM) figure of merit. For example, various implementations of an elastic power header device are utilized as programmable resistances to permit the power supply lines to reach a maximum voltage. Allowing the power supply lines to reach the reference voltage allows more flexibility in read margin and read stability. Furthermore, this additional flexibility can be controlled by means for adjusting a voltage. This adjustment voltage can fine-tune the programmable resistances so that the read margin can be more conveniently controlled.

Elastic power for read margin

A dynamic latch includes a first stage for receiving an input data value and for providing true and complement logic values representing the input data value; a second stage for receiving the true and complement logic values into first and second dynamic node, when a control signal is active; and a holding that outputs the true and complement logic values while the control signal is active. The second stage may provide a feedback signal to the first stage to block propagation of changes in the input data value after the true and complement logic values have been received. The feedback signal may be derived, for example, from logic values on the dynamic nodes. A holding circuit may be provided.

Dynamic dual output latch

An elastic power header device and methods of operation are provided to improve both the read and the write margin of static random access memory (SRAM) cells by increasing read stability, reducing read disturbance and improving the Signal to Noise Margin (SNM) figure of merit. For example, various implementations of an elastic power header device are utilized as programmable resistances to permit the power supply lines to reach a maximum voltage. Allowing the power supply lines to reach the reference voltage allows more flexibility in read margin, write margin and read stability. Furthermore, this additional flexibility can be controlled by means for adjusting a voltage. This adjustment voltage can fine-tune the programmable resistances so that the read margin and the write margin can be more conveniently controlled.

Elastic power for read and write margins

A timing-constrained circuit (e.g., a self-timed circuit) of optimal performance is achieved by allowing the delay of the circuit to be changed dynamically as a function of operating conditions (e.g., operating voltages or temperatures). The delay of timing signals in the timing-constrained circuit for a given operating condition may be selected to have the minimum margin for that operating condition among the available delays to maximize performance over the entire dynamic range of operating conditions.

Dynamic voltage scaling for self-timed or racing paths

A hybrid dual match line circuit may include a hit match line coupled to a first group of load devices and a miss match line coupled to discharge through a second group of load devices. Both the hit and miss match lines may be configured to be precharged to an asserted state. Each of the second group of load devices may be activated for discharging by a respective miss signal. The hit match line may be additionally coupled to discharge through first and second discharge path respectively activated for discharging in response to a hit signal and a read/write enable signal. The hit and miss match lines may be electrically isolated from one another, such that when one or more of the respective miss signals are asserted, current from the hit match line does not discharge through the miss match line.

Hybrid dual match line architecture for content addressable memories and other data structures

Dual match line circuits having race condition improvements. A dual match line circuit may include precharge logic configured to precharge each of a hit match line, a miss match line and an evaluate node to an asserted state, where a coupling device couples the hit and miss match lines to the evaluate node. The miss match line may discharge through a number of load devices that may be activated by respective miss signals. A positive feedback circuit coupled to the miss match line may accelerate its discharge. The hit match line may be additionally coupled to discharge through a discharge path. The hit and miss match lines may be electrically isolated from one another, such that when any of the respective miss signals is asserted, current from the hit match line does not discharge through the miss match line.

Race condition improvements in dual match line architectures

A dual match line circuit may include precharge logic configured to precharge each of a hit match line, a miss match line and an evaluate node to an asserted state, where a coupling device couples the hit and miss match lines to the evaluate node. The miss match line may discharge through a number of load devices that may be activated by respective miss signals. The hit match line may be additionally coupled to discharge through a pair of devices connected in series, one of which may be activated by a hit signal, and the other of which may be activated by the miss match line. The hit and miss match lines may be electrically isolated from one another, such that when any of the respective miss signals is asserted, current from the hit match line does not discharge through the miss match line.

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Santa Clara, CA, United States of America

Ajay Bhatia