Non-volatile RAM with integrated compact static RAM load configuration
First Claim
1. A non-volatile static random access memory (NVSRAM) cell, comprising:
- power supply means for supplying electrical power to said cell relative to a reference potential;
a flip flop having a true data node and a complement data node, the flip flop comprising a pair of cross-coupled flip flop transistors, one flip flop transistor having a control terminal connected to the true data node, a reference terminal electrically connected to the reference potential and an output terminal connected to the complement data node, and the other flip flop transistor having a control terminal connected to the complement data node, a reference terminal electrically connected to the reference potential and an output terminal connected to the true data node;
a pair of non-volatile circuits respectively connected to said true and complement data nodes, each non-volatile circuit comprising a programmable threshold voltage device having a gate terminal which is receptive of program and erase signals which establish different levels of threshold voltage for that programmable threshold voltage device in accordance with the level of the signal at its respective data node, a first transistor switch means having a control terminal which is receptive of a signal to allow the first transistor switch means to conduct and connect a corresponding programmable threshold voltage device to its respective data node when the program and erase signals are applied and when a data recall operation occurs, and a second switch means having a control terminal which is receptive of a signal to allow the second switch means to selectively conduct current from the power supply means through a corresponding programmable threshold voltage device and first transistor switch means to its respective data node during the data recall operation to establish a signal level at its respective data node related to the threshold voltage of the corresponding programmable threshold voltage device;
means commonly connecting the gate terminals of the programmable threshold voltage devices for conducting the program and erase signals to the gate terminals of the programmable threshold voltage devices; and
conductor means connected to the power supply means and including an integral resistive load for conducting power to the true data node and also including another integral resistive load for conducting power to the complement data node, the conductor means and the integral resistive loads energizing the flip flop to maintain the signals at the data nodes resulting from the previous operation of the flip flop as a static random access memory during application of the erase signals to the programmable threshold voltage devices.
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Abstract
A non-volatile random access memory (NVRAM) cell of condensed size employs a pair of programmable threshold voltage devices, e.g. MNOS (metal nitride oxide semiconductor), SNOS (silicon nitride oxide semiconductor), SONOS (silicon oxide-nitride-oxide semiconductor) or floating gate transistors, in which different threshold voltage levels are established in accordance with the data signal levels existing on the data nodes of a flip flop, when the volatile data is stored in the programmable devices. During recall of the non-volatile stored data to the data nodes of the flip flop, the programmable devices actively conduct current to the data nodes to set the flip flop in the same state that existed when the data was stored. Power is supplied to the flip flop independently of the power supplied to the programmable devices. A single polysilicon conductor forms gates of transistors which connect the programmable devices to the data nodes and the gates of the flip flop transistors. A load device for each data node is integrated in the single polysilicon conductor. A dynamic program inhibit capability is achieved in each programmable device during the store operation, by applying a series of programming signal pulses.
96 Citations
19 Claims
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1. A non-volatile static random access memory (NVSRAM) cell, comprising:
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power supply means for supplying electrical power to said cell relative to a reference potential; a flip flop having a true data node and a complement data node, the flip flop comprising a pair of cross-coupled flip flop transistors, one flip flop transistor having a control terminal connected to the true data node, a reference terminal electrically connected to the reference potential and an output terminal connected to the complement data node, and the other flip flop transistor having a control terminal connected to the complement data node, a reference terminal electrically connected to the reference potential and an output terminal connected to the true data node; a pair of non-volatile circuits respectively connected to said true and complement data nodes, each non-volatile circuit comprising a programmable threshold voltage device having a gate terminal which is receptive of program and erase signals which establish different levels of threshold voltage for that programmable threshold voltage device in accordance with the level of the signal at its respective data node, a first transistor switch means having a control terminal which is receptive of a signal to allow the first transistor switch means to conduct and connect a corresponding programmable threshold voltage device to its respective data node when the program and erase signals are applied and when a data recall operation occurs, and a second switch means having a control terminal which is receptive of a signal to allow the second switch means to selectively conduct current from the power supply means through a corresponding programmable threshold voltage device and first transistor switch means to its respective data node during the data recall operation to establish a signal level at its respective data node related to the threshold voltage of the corresponding programmable threshold voltage device; means commonly connecting the gate terminals of the programmable threshold voltage devices for conducting the program and erase signals to the gate terminals of the programmable threshold voltage devices; and conductor means connected to the power supply means and including an integral resistive load for conducting power to the true data node and also including another integral resistive load for conducting power to the complement data node, the conductor means and the integral resistive loads energizing the flip flop to maintain the signals at the data nodes resulting from the previous operation of the flip flop as a static random access memory during application of the erase signals to the programmable threshold voltage devices. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19)
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Specification