ROM embedded DRAM with bias sensing
AssigneeMicron Technology, Inc.
InventorsScott Derner, Casey Kurth, Phillip G. Wald
Life of this patent
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Abstract
A ROM embedded DRAM that provides ROM cells that can be programmed to a single state. Bias techniques are used to read un-programmed ROM cells accurately. Sense amplifier circuitry can be offset in one embodiment to default to the un-programmed state. In another embodiment, bias circuitry is coupled to bit lines to favor the un-programmed state. Further, a differential pre-charge operation can also be used in another embodiment. The ROM embedded DRAM allows for simplifier fabrication and programming of the ROM cells, while providing accurate dual state functionality.
Claims14
A read only memory (ROM) embedded dynamic random access memory (DRAM) device comprising:
- a plurality of DRAM cell capacitors, wherein a portion of the plurality of DRAM cell capacitors are programmed as ROM cells in a non-volatile manner to a first data state;
- first and second digit lines, the first digit line is selectively couplable to the ROM cells;
- sense circuitry coupled to the first and second digit lines;
- and
- a pre-charge circuit to charge the first and second digit lines to first and second voltage level, respectively.
A method of reading a read-only memory (ROM) cell comprising:
- precharging a first digit line to a first voltage level;
- precharging a second digit line to a second voltage level;
- coupling a ROM cell to the first digit line;
- and
- comparing a voltage of the first digit line to a voltage of the second digit line.
A read only memory (ROM) embedded dynamic random access memory (DRAM) device comprising:
- a plurality of DRAM cell capacitors, wherein a portion of the plurality of DRAM cell capacitors are programmed as ROM cells in a non-volatile manner to a first data state;
- first and second digit lines, the first digit line is selectively couplable to the ROM cells;
- sense circuitry coupled to the first and second digit lines;
- and
- a pre-charge circuit to charge the first and second digit lines to ½ Vcc and greater than ½ Vcc but less than or equal to Vcc, respectively.
Dependencies are inferred from the claim text.