HANDLING OF WRITE OPERATIONS WITHIN A MEMORY DEVICE

• US 20130258760A1
• Filed: 04/02/2012
• Published: 10/03/2013
• Est. Priority Date: 04/02/2012
• Status: Active Grant

• Current Assignee: Arm Limited (SoftBank Group Corp.)
• Original Assignee: Arm Limited (SoftBank Group Corp.)
• Inventors: HOLD, Betina
• Granted Patent: US 9,064,561 B2
• Time in Patent Office: Days
• US Class Current: 365/154
• CPC Class Codes: G11C 11/00 Digital stores characterised by the use of particular electric or magnetic storage elements; Storage elements therefor G11C14/00 - G11C21/00 take precedence
• CPC Class Codes: G11C 11/412 using field-effect transistors only
• CPC Class Codes: G11C 11/419 Read-write [R-W] circuits
• CPC Class Codes: G11C 7/1006 Data managing, e.g. manipulating data before writing or reading out, data bus switches or control circuits therefor
• CPC Class Codes: G11C 7/1078 Data input circuits, e.g. write amplifiers, data input buffers, data input registers, data input level conversion circuits
• CPC Class Codes: G11C 7/227 Timing of memory operations based on dummy memory elements or replica circuits

Abstract

A memory device includes an array of memory cells arranged into a plurality of rows and columns and having a plurality of word lines and a plurality of bit lines passing through the array. The memory cells in each row are activated via a word line signal on the corresponding word line, and the memory cells in each column are coupled to an associated bit line pair via which data is written into an activated memory cell of the column during a write operation and data is read from the activated memory cell of the column during a read operation. A dummy column of dummy memory cells is provided and includes a plurality of loading dummy memory cells for providing a load to the at least one dummy bit line, and at least one write timing dummy memory cell coupled to a dummy word line.

Claims

1. A memory device comprising:

an array of memory cells arranged into a plurality of rows and columns and having a plurality of word lines and a plurality of bit lines passing through the array, the memory cells in each row being activated via a word line signal on the corresponding word line, and the memory cells in each column being coupled to an associated at least one bit line via which data is written into an activated memory cell of the column during a write operation and data is read from an activated memory cell of the column during a read operation;

control circuitry configured to control signals supplied to the word lines and bit lines of the array in order to control said write operation and said read operation;

a dummy column of dummy memory cells associated with said array, said dummy column including at least one dummy bit line to which said dummy memory cells are connected, the dummy memory cells including a plurality of loading dummy memory cells for providing a load to said at least one dummy bit line, and at least one write timing dummy memory cell coupled to a dummy word line;

dummy write driver circuitry coupled to said at least one dummy bit line;

the control circuitry being configured, during said write operation, to activate each of said at least one write timing dummy memory cell via the dummy word line, and to cause the dummy write driver circuitry to control a voltage on the at least one dummy bit line so as to cause a state flip condition to occur within said at least one write timing dummy memory cell; and

write detection circuitry configured, on occurrence of the state flip condition, to issue a write terminate signal to the control circuitry to terminate the write operation.

2. A memory device as claimed in claim 1, wherein:

said at least one dummy bit line comprises first and second dummy bit lines;

the dummy write driver circuitry is connected to said first dummy bit line; and

said write detection circuitry is connected to said second dummy bit line.

3. A memory device as claimed in claim 2, further comprising:

dummy precharge circuitry configured to precharge said first dummy bit line to a first voltage level and said second dummy bit line to a second voltage level;

the dummy write driver circuitry being configured during said write operation to drive said first dummy bit line towards said second voltage level; and

the write detection circuitry being configured to detect said state flip condition by detecting when a change in the internal stored state of said at least one write timing dummy memory cell causes the voltage on said second dummy bit line to transition from said second voltage level towards said first voltage level.

4. A memory device as claimed in claim 3, further comprising flip assist circuitry configured to assist the at least one write timing dummy memory cell in transitioning the voltage on said second dummy bit line towards said first voltage level.

5. A memory device as claimed in claim 2, wherein:

said second dummy bit line is separated into first and second portions, the first portion being connected to said at least one write timing dummy memory cell, and the second portion being connected to said plurality of loading dummy memory cells; and

said write detection circuitry is connected to said first portion of the second dummy bit line.

6. A memory device as claimed in claim 2, wherein:

each dummy memory cell is a six transistor (6T) SRAM cell including first and second pass gates for coupling the memory cell to said first and second dummy bit lines; and

each write timing dummy memory cell is configured to have its first pass gate controlled by a signal on the dummy word line to connect the write timing dummy memory cell to the first dummy bit line during the write operation.

7. A memory device as claimed in claim 6, wherein each write timing dummy memory cell is configured to have its second pass gate bypassed such that the write timing dummy memory cell is permanently connected to the second dummy bit line.

8. A memory device as claimed in claim 6, wherein:

each loading dummy memory cell has both of its first and second pass gates permanently turned off so that the stored state within that loading dummy memory cell is not affected by the voltage on the first and second dummy bit lines.

9. A memory device as claimed in claim 1, further comprising:

state control circuitry configured to supply dual supply voltages to the plurality of loading dummy memory cells and to control the supply voltage values of said dual supply voltages in order to set the data values stored in the plurality of loading dummy memory cells to act as a worst case load condition on the at least one dummy bit line during the write operation.

10. A memory device as claimed in claim 1, wherein the number of write timing dummy memory cells provided in the dummy column is programmable at design time.

11. A memory device as claimed in claim 1, wherein:

said dummy memory cells include at least one read timing dummy memory cell coupled to said dummy word line;

the control circuitry being configured, during said read operation, to activate each of said at least one read timing dummy memory cell via a signal on the dummy word line and a read enable signal;

said at least one read timing dummy memory cell being configured, when activated, to cause a voltage on said at least one dummy bit line to transition from a first voltage level towards a second voltage level;

the memory device further comprising read detection circuitry configured, on detection of the voltage on said at least one dummy bit line transitioning towards said second voltage level during said read operation, to issue a read terminate signal to the control circuitry to terminate the read operation.

12. A memory device as claimed in claim 11, wherein:

each read timing dummy memory cell comprises a six transistor (6T) SRAM memory cell having four transistors disabled, such that the remaining two transistors are coupled in series between said at least one dummy bit line and said second voltage level;

dummy precharge circuitry is configured to precharge said at least one dummy bit line to said first voltage level prior to the read operation; and

during said read operation, one of the remaining two transistors is turned on by the read enable signal and the other of the remaining two transistors is turned on by the signal on the dummy word line.

13. A memory device as claimed in claim 11, further comprising:

state control circuitry configured to supply dual supply voltages to the plurality of loading dummy memory cells and to control the supply voltage values of said dual supply voltages in order to set the data values stored in the plurality of loading dummy memory cells to act as a worst case load condition on the at least one dummy bit line during the read operation.

14. A memory device as claimed in claim 11, wherein the number of read timing dummy memory cells provided in the dummy column is programmable at design time.

15. A memory device as claimed in claim 1, wherein said dummy word line is routed so as to provide a delay in propagation of an activation signal to the at least one write timing dummy memory cell having regard to a worst case propagation delay of a corresponding activation signal sent to an addressed memory cell within the array.

16. A method of controlling timing of a write operation within a memory device comprising an array of memory cells arranged into a plurality of rows and columns and having a plurality of word lines and a plurality of bit lines passing through the array, the memory cells in each row being activated via a word line signal on the corresponding word line, and the memory cells in each column being coupled to an associated at least one bit line via which data is written into an activated memory cell of the column during a write operation and data is read from an activated memory cell of the column during a read operation, the memory device further having control circuitry for controlling signals supplied to the word lines and bit lines of the array in order to control said write operation and said read operation, and the method comprising:

providing a dummy column of dummy memory cells associated with said array, said dummy column including at least one dummy bit line to which said dummy memory cells are connected, the dummy memory cells including a plurality of loading dummy memory cells for providing a load to said at least one dummy bit line, and at least one write timing dummy memory cell coupled to a dummy word line;

during said write operation, activating each of said at least one write timing dummy memory cell via the dummy word line, and controlling a voltage on the at least one dummy bit line so as to cause a state flip condition to occur within said at least one write timing dummy memory cell; and

on occurrence of the state flip condition, issuing a write terminate signal to the control circuitry to terminate the write operation.

17. A memory device comprising:

an array of memory cell means arranged into a plurality of rows and columns and having a plurality of word line means and a plurality of bit line means passing through the array, the memory cell means in each row for activation via a word line signal on the corresponding word line means, and the memory cell means in each column for coupling to an associated at least one bit line means via which data is written into an activated memory cell means of the column during a write operation and data is read from an activated memory cell means of the column during a read operation;

control means for controlling signals supplied to the word line means and bit line means of the array in order to control said write operation and said read operation;

a dummy column of dummy memory cell means associated with said array, said dummy column including at least one dummy bit line means for connecting to said dummy memory cell means, the dummy memory cell means including a plurality of loading dummy memory cell means for providing a load to said at least one dummy bit line means; and

at least one write timing dummy memory cell means for coupling to a dummy word line means;

dummy write driver means for coupling to said at least one dummy bit line means;

the control means, during said write operation, for activating each of said at least one write timing dummy memory cell means via the dummy word line means;

the dummy write driver means, during said write operation, for controlling a voltage on the at least one dummy bit line means so as to cause a state flip condition to occur within said at least one write timing dummy memory cell means; and

write detection means, on occurrence of the state flip condition, for issuing a write terminate signal to the control means to terminate the write operation.