Qualcomm Incorporated

Chang Ho Jung

Zhiqin Chen

Nan Chen

Cheng Zhong

Sei Seung Yoon

Hari Rao

A memory device includes a core array that includes memory cells. The memory device also includes a headswitch coupled to the core array and a positive supply voltage. The headswitch reduces leakage current from the core array by disconnecting the core array from the positive supply voltage. Additionally, head switches are added for pre-charge devices to further reduce leakage current.

Leakage reduction in memory devices

A pseudo-dual port memory address multiplexing system includes a control circuit operative to identify a read request and a write request to be accomplished during a single clock cycle. A self time tracking circuit monitors a read operation and generates a switching signal when the read operation is determined to be complete. A multiplexer is responsive to the switching signal for selectively providing a read address and a write address to a memory address unit at the proper time.

Address multiplexing in pseudo-dual port memory

A sense margin is improved for a read path in a memory array. Embodiments improve the sense margin by using gates with a lower threshold voltage in a read column multiplexer. A cross coupled keeper can further improve the sense margin by increasing a voltage level on a bit line storing a high value, thereby counteracting leakage on the 'high' bit line.

SRAM yield enhancement by read margin improvement

Multi-ported memory systems (e.g., register files) employ self-timing for operational synchronization. Thus, rather than using a reference clock duty cycle for operational synchronization, as in conventional multi-ported register files, embodiments of the present disclosure employ self-timing for such operational synchronization. According to certain embodiments, self-timing is employed to synchronize all the internal events within the memory so that all the events are spaced in time for appropriate synchronization. For instance, the completion of one event leads to triggering another event, the completion of which leads to triggering another event, and so on. Thus, in one embodiment, the self-timing is achieved by referencing the operational events with the memory (or register file) to each other, rather than to a reference clock duty cycle.

Self-timing for a multi-ported memory system

Techniques for generating clock and control signals to achieve good performance for read and write operations in memory devices are described. In one design, a clock and control signal generator within a memory device includes first and second clock generators, first and second control signal generators, and a reset circuit. The first clock generator generates a first clock signal used for read and write operations. The second clock generator generates a second clock signal used for write operations. The reset circuit generates at least one reset signal for the first and second clock generators. The reset signal(s) may have timing determined based on loading due to dummy cells. The first control signal generator generates control signals used for read and write operations based on the first clock signal. The second control signal generator generates control signals used for write operations based on the second clock signal.

Clock and control signal generation for high performance memory devices

A method accurately tracks a bit line maturing time for compiler memory. The method includes enabling a dummy word line in response to an internal clock signal. The dummy word line is enabled prior to enabling a real word line. A dummy bit line is matured in response to enabling of the dummy word line. The dummy bit line matures at a same rate that a real bit line matures. The method also includes disabling the dummy word line in response to determining a threshold voltage differential based on monitoring maturation of the dummy bit line. The real word line is enabled a predefined delay after enabling of the dummy word line. Similarly, the word line is disabled the predefined delay after disabling of the dummy word line. In response to disabling the dummy word line, a sense enable signal is generated.

Advanced bit line tracking in high performance memory compilers

A memory includes a global read line and a plurality of banks. For each bank, the memory includes a sense amplifier. A discharge circuit discharges the global read line if any one of a plurality of the sense amplifiers is enabled and is outputting a signal having a first digital logic value onto an input lead of the discharge circuit. In this way, the sense amplifiers share the discharge circuit. In one example, the memory includes a pair of differential read lines that are precharged to begin a read operation. After precharging, if either of two sense amplifiers is enabled and outputting the first digital logic value, then a first discharge circuit discharges a first of the global read lines. If either of two sense amplifiers is enabled and outputting the second digital logic value, then a second discharge circuit discharges a second of the global read lines.

Semi-shared sense amplifier and global read line architecture

A memory device that can provide good timing margins for read and write operations is described. In one design, the memory device includes a memory array, a timing control circuit, and an address decoder. The memory array includes memory cells for storing data and dummy cells to mimic the memory cells. The timing control circuit generates at least one control signal used for writing data to the memory cells and having timing determined based on the dummy cells. The timing control circuit may generate a pulse on an internal clock signal with a driver having configurable drive strength and a programmable delay unit. The pulse duration may be set to obtain the desired write timing margin. The address decoder activates word lines for rows of memory cells for a sufficiently long duration, based on the internal clock signal, to ensure reliable writing of data to the memory cells.

Memory device with delay tracking for improved timing margin

A memory has a novel self-timing circuit that generates internal memory control signals. Control signals may include an address latch enable signal, a decoder enable signal, and a sense amplifier enable signal. The circuit has a timing loop whose timing mimics the timing of an access of the real memory. The timing loop includes dummy bit cells of identical construction to bit cells in the real array being accessed, a programmable delay circuit, and a programmable accelerator circuit. The dummy bit cells cause the timing of the control signals to track speed changes in the memory array being accessed. The programmable delay and accelerator circuits are usable to slow or speed the timing loop. The programmable delay and accelerator circuits are usable to achieve a desired yield to memory access speed tradeoff. Flexibility of the timing loop allows a memory to be designed before memory access timing characteristics are fixed.

Self-timing circuit with programmable delay and programmable accelerator circuits

A pseudo-dual port memory has a first port, a second port, and an array of six-transistor memory cells. A first memory access is initiated upon a rising edge of a first clock signal received onto the first port. A second memory access is initiated in response to a rising edge of a second clock signal received onto the second port. If the rising edge of the second clock signal occurs within a first period of time, then the second memory access is initiated immediately following completion of the first memory access in pseudo-dual port fashion. If the rising edge of the second clock signal occurs later within a second period of time, then the second memory access is delayed until after a second rising edge of the first clock signal. The durations of the first and second memory accesses do not depend on the duty cycles of the clock signals.

Pseudo-dual port memory having a clock for each port

A pseudo-dual port memory performs both a first memory access operation and a second memory access operation in a single period of an externally supplied clock signal CLK. The signal CLK is used to latch a first address for the first operation and a second address for the second operation. Control circuitry generates first control signals that initiate the first operation. The time duration of the first operation depends upon a delay through a delay circuit. A precharge period follows termination of the first operation. The time duration of the precharge period depends upon a propagation delay through the control circuit. The memory access of the second operation is initiated following termination of the precharging. The time duration of the second memory access depends on a delay through the delay circuit. The time when the second operation is initiated is independent of the duty cycle of CLK.

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San Diego, CA, United States of America

Chang Ho Jung