National Semiconductor Corporation

Robert A Kertis

Douglas D Smith

Terrance L Bowman

A self-locking load structure for Random Access Memories is disclosed. The load structure remains coupled to the memory cell during read operations but automatically decouples from the memory during write operations. No separate decoded WRITE command must be sent to the load structure to couple and decouple the structure from the memory cell.

Self-locking load structure for static RAM

A method for detecting voltage supply short circuits in integrated circuits and a circuit for implementing that method is disclosed. Entire rows of memory cells in an SRAM are coupled to a single sense line. The sense line to each row is activated individually. The sense lines are in turn coupled to a current sensing circuit. If a short exists on any memory cell in a given row, the current sensing circuit generates a low output, indicating a short circuit.

Short circuit detector circuit for memory arrays

The present invention provides an ECL EPROM circuit which uses a MOS memory cell. The invention includes a technique for programming the memory cell using MOS voltage levels, and also includes circuitry for reading the memory cell at ECL voltage levels. Thus, the programming and reading paths are split to give the ease of programming and the reprogrammability of MOS EPROM devices combined with the reading speed of PROM devices using ECL voltage levels. In one embodiment, two parallel paths are provided to a memory cell to enable it to separately receive reading and writing (programming) signals. The reading path employs ECL components for reading the cell, while the writing path contains MOS components for programming and verifying the cell. The memory cell itself contains a MOS memory element, an ECL pass element, and a sense element coupling the MOS memory element to the ECL pass element. The MOS memory element is coupled to the programming (writing) path, and the ECL pass element is coupled to the read path with a bipolar output transistor.

ECL EPROM with CMOS programming

A bipolar recovery circuit for a static random access memory cell is described. The circuit corrects reverse emitter-base breakdown which occurs in the known common base node writing recovery circuits. The circuit is simple, requiring little silicon chip area to fabricate. In a preferred embodiment, a separate recovery circuit is coupled to each of the true output line and the complement output line of the memory cell.

Individual bit line recovery circuits

A switching circuit for SRAM memory cells is disclosed. The circuit electronically decouples input lines to sense amplifiers from unselected arrays of memory cells. The decoupling results in a large decrease in the amount of parasitic capacitance that the selected inputs would encounter.

Shared BiCMOS sense amplifier

A power transition circuit protects a bipolar-CMOS (BiCMOS) circuit during power transitions. Reference signals proportional to the voltage supplied to the protected circuit are monitored, and the power transition circuit determines from the voltage differential between the reference signals whether a power transition is occurring. If a transition is present, the transition circuit disables the protected BiCMOS circuit for as long as the power transition exists. An independent input signal allows the power transition circuit to disable the protected BiCMOS circuit in response to other conditions.

BiCMOS power transition circuit

A BiCMOS write-recovery method and circuit for recovering bit lines in a digital memory system provides approximately 1 nS recovery time and allows a 256K BiCMOS SRAM to achieve 10 nS access time. All bit lines in the memory system connected to a column not being read are held at a high potential, approximately equal to the upper power supply. During a write, one bit line is pulled low and its complementary bit line is clamped with a bipolar transistor to an intermediate potential, thereby preloading the complementary bit line. Following a write, the bit line that was pulled low is pulled up with a bipolar transistor to the intermediate voltage. Simultaneously, the bit line and the complementary bit line are shunted together, then returned to the high potential. Undesired bootstrap capacitance effects in the bipolar transistors are minimized by connecting a plurality of pull-up transistors in parallel, and by feeding the clamping transistors with low impedance drivers.

BiCMOS write-recovery circuit

A biCMOS interface circuit receives a plurality of incoming signals at a first level and supplies a plurality of output signals at a second level. The interface circuit establishes control voltages which are used to maintain an identical trip point in each of a plurality of translator circuits. Generally, the trip point is set at midway between the 'high' and the 'low' levels of the incoming logic signal. The control voltages assure reliable performance over a wide operating environment.

Low-power bipolar-CMOS interface circuit

A BiCMOS voltage reference generator circuit generates and maintains a reference voltage within 3 mV over an 80.degree. C. temperture range and over a 1 volt change in power supply level. The circuit uses feedback from the output of the reference voltage generator to the current source supplying current to the voltage reference generator. This feedback increases the effective output impedance of the current source, making the reference voltage output substantially independent of power supply variations. The circuit operates with power supply differential as low as about 3 volts, and preferably is fabricated from bipolar transistors and MOS transistors on the same chip.

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Puyallup, WA, United States of America

Robert A Kertis