Read-only memory (ROM) bitcell, array, and architecture
View Patent ↗Embodiments provide improved memory bitcells, memory arrays, and memory architectures. In an embodiment, a memory cell comprises a transistor having drain, source, and gate terminals; and a plurality of program nodes, with each of the program nodes charged to a pre-determined voltage and coupled to a respective one of a plurality of bit lines.
1. A memory cell, comprising:
a transistor having drain, source, and gate terminals; and
a plurality of program nodes, each of said program nodes charged to a pre-determined voltage and coupled to a respective one of a plurality of bit lines;
wherein at most one of the plurality of program nodes is coupled to the drain terminal of the transistor to program the memory cell to store at least one information bit.
2. The memory cell of claim 1 , wherein exactly one of the plurality of program nodes is coupled to the drain terminal of the transistor.
3. The memory cell of claim 1 , wherein a value of the at least one information bit stored in the memory cell is determined based on which, if any, of the plurality of program nodes is coupled to the drain terminal of the transistor.
4. The memory cell of claim 1 , wherein a value of the at least one information bit stored in the memory cell is determined based on voltage values observed on the plurality of bit lines.
5. The memory cell of claim 1 , wherein the gate terminal of the transistor is coupled to a word line, and the source terminal of the transistor is coupled to a common pull down (CPD) line.
6. The memory cell of claim 5 , wherein the word line and the CPD line are activated simultaneously to access the at least one information bit stored in the memory cell.
7. The memory cell of claim 1 , wherein the program nodes are charged to said pre-determined voltage at manufacture time.
8. A memory array, comprising:
a plurality of memory cells, each of the plurality of memory cells having respective row and column addresses, and associated with respective word line, common pull down (CPD) line, and bit line set;
wherein same row address memory cells of the plurality of memory cells share a common word line; and
wherein adjacent column address memory cells of the plurality of memory cells share one of a common CPD line and a common bit line set.
9. The memory array of claim 8 , wherein a memory cell of the plurality of memory cells is accessed by activating its respective word line and CPD line.
10. The memory array of claim 8 , wherein the memory array is configured such that same row address, adjacent column address memory cells of the plurality of memory cells that share a common CPD line are accessed simultaneously.
11. The memory array of claim 8 , wherein the memory array is configured such that adjacent column address memory cells of the plurality of memory cells that share a common bit line set are accessed separately.
12. The memory array of claim 8 , wherein same column address memory cells of the plurality of memory cells share a common CPD line and a common bit line set.
13. The memory array of claim 12 , wherein the memory array is configured such that said same column address memory cells are accessed separately.
14. The memory array of claim 12 , wherein each of the plurality of memory cells comprises:
a transistor having drain, source, and gate terminals; and
a plurality of program nodes, each of said program nodes charged to a pre-determined voltage and coupled to a respective line of the bit line set associated with the memory cell;
wherein at most one of the plurality of program nodes is coupled to the drain terminal of the transistor to program the memory cell to store at least one information bit.
15. The memory cell of claim 14 , wherein a value of the at least one information bit stored in the memory cell is determined based on which, if any, of the plurality of program nodes is coupled to the drain terminal of the transistor.
16. The memory array of claim 8 , wherein the memory array is divided into one or more memory blocks, each memory block comprising a separate set of memory cells of the plurality of memory cells and dedicated CPD lines and bit line sets for accessing said separate set of memory cells.
17. The memory array of claim 16 , wherein said each memory block is divided into a top half array of memory cells and a bottom half array of memory cells, wherein said top and bottom half arrays have separate CPD lines and CPD driver circuitry.
18. The memory array of claim 17 , wherein said top and bottom half arrays share bit line sets.
19. The memory array of claim 16 , wherein said each memory block further comprises an I/O circuitry coupled to said dedicated bit line sets.
20. The memory array of claim 19 , wherein the I/O circuit comprises a decoder circuit.