FUSE DATA ACQUISITION

• US 20090067252A1
• Filed: 02/18/2008
• Published: 03/12/2009
• Est. Priority Date: 09/06/2007
• Status: Active Grant

• Current Assignee: Micron Technology, Inc.
• Original Assignee: Micron Technology, Inc.
• Inventors: Donnola, Stefano, Naso, Giovanni
• Granted Patent: US 7,738,310 B2
• Time in Patent Office: Days
• US Class Current: 365/185.190
• CPC Class Codes: G11C 17/18 Auxiliary circuits, e.g. for writing into memory

Abstract

One or more embodiments of the present disclosure provide methods, devices, and systems for operating memory devices having fuse circuits. One method embodiment includes detecting a signal indicating whether a voltage used during operation of at least one of a number of fuse circuits has reached a threshold level, initializing at least one of the number of fuse circuits in response to detecting that the voltage has reached the threshold level, and reading an output of at least one of the number of fuse circuits at least partially in response to a detected state change of an output of the at least one initialized fuse circuit.

Claims

1. A method of operating a memory device, the method comprising:

detecting a signal indicating whether a voltage used during operation of at least one of a number of fuse circuits has reached a threshold level;

initializing at least one of the number of fuse circuits in response to detecting that the voltage has reached the threshold level; and

reading an output of at least one of the number of fuse circuits at least partially in response to a detected state change of an output of the at least one initialized fuse circuit.

2. The method of claim 1, wherein detecting that the voltage has reached a threshold level includes receiving a power on reset (POR) signal from a threshold detector indicating the voltage has reached the threshold level.

3. The method of claim 2, wherein detecting the signal indicating whether the voltage has reached the threshold level is performed during power up of the memory device.

4. The method of claim 3, wherein initializing includes providing a signal to a reset transistor coupled to a latch of the at least one fuse circuit being initialized which causes an output of the latch to be at a first state;

and

wherein the method includes;

detecting when the output of the latch of the at least one initialized fuse circuit changes to a second state; and

determining a state of an output of a latch of the at least one fuse circuit being read at least partially in response to the detected change to the second state.

5. The method of claim 4, wherein detecting includes detecting when the output of the latch of the at least one initialized fuse circuit changes from a logic low state to a logic high state.

6. The method of claim 1, wherein the at least one fuse circuit being initialized and the at least one fuse circuit being read include a programmable element and a latch to which data stored by the element is transferred during a read of the fuse circuits, and wherein the method includes programming the element of the at least one fuse circuit being reset differently than the element of the at least one fuse circuit being read.

7. The method of claim 6, wherein the method includes:

adjusting a floating gate transistor of the programmable element of the at least one fuse circuit being initialized to a first threshold voltage (Vt) level; and

adjusting a floating gate transistor of the programmable element of the at least one fuse circuit being read to a second Vt level, wherein the second Vt level is greater in magnitude than the first Vt level.

8. The method of claim 7, wherein the method includes:

adjusting the floating gate transistor of the programmable element of the at least one fuse circuit being initialized to a first Vt level that is between about −

0.05V and −

1.0V; and

adjusting the floating gate transistor of the programmable fuse element of the at least one fuse circuit being read to a second Vt level that is between about −

2.0V and −

3.0V.

9. A method of operating a memory device having a number of fuse circuits, the method comprising:

storing a data value in a memory cell of a fuse circuit by adjusting a threshold voltage (Vt) level of the cell to a first Vt level;

storing the data value in a memory cell of at least one other fuse circuit by adjusting a Vt level of the cell of the at least one other fuse circuit to a second Vt level, the second Vt level greater in magnitude than the first Vt level;

while a voltage used during operation of the device is ramping, providing a reset signal to the fuse circuit having the memory cell adjusted to the first Vt level at least partially in response to detecting that the voltage has reached a threshold level, wherein, an output of a latch of the fuse circuit having the memory cell adjusted to the first Vt level is reset to a reset data value;

initiating a transfer of the stored data value from the memory cell adjusted to the first Vt level to the latch and initiating a transfer of the stored data value from the memory cell of the at least one other fuse circuit having the memory cell adjusted to the second Vt level to an other latch;

detecting when the output of the latch of the fuse circuit having the memory cell adjusted to the first Vt level changes from the reset data value to the stored data value; and

reading an output of the an other latch of the at least one other fuse circuit having the memory cell adjusted to the second Vt level after detecting the output change of the latch of the fuse circuit having the memory cell adjusted to the first Vt level.

10. The method of claim 9, wherein initiating the transfer of the stored data value to the latch of the fuse circuit having the memory cell adjusted to the first Vt level includes:

applying a ramping voltage to an input node of the fuse circuit having the memory cell adjusted to the first Vt level; and

applying a read voltage to a control gate of the memory cell adjusted to the first Vt level, the read voltage sufficient to place the memory cell adjusted to the first Vt level in a conducting state.

11. The method of claim 10, wherein initiating the transfer of the stored data value to the an other latch of the at least one other fuse circuit having the memory adjusted to the second Vt level includes:

applying the ramping voltage to an input node of the at least one other fuse circuit; and

applying the read voltage to a control gate of the memory cell adjusted to the second Vt level.

12. The method of claim 11, wherein applying the read voltage includes:

applying a read voltage of about 0V to the control gate of the memory cell adjusted to the first Vt level; and

applying the read voltage of about 0V to the control gate of the memory cell adjusted to the second Vt level.

13. The method of claim 10, wherein the method includes providing a signal that indicates when commands can be given for the memory device to operate at least partially in response to the detected output change of the latch of the fuse circuit having the memory cell adjusted to the first Vt level.

14. The method of claim 10, wherein the method includes erasing the memory cell of the fuse circuit having the memory cell adjusted to the first Vt level and erasing the memory cell of the at least one other fuse circuit having the memory cell adjusted to the second Vt level.

15. The method of claim 14, wherein the method includes:

storing an other data value in a memory cell of at least a third fuse circuit by adjusting a Vt level of the cell of the at least the third fuse circuit to a third Vt level, the third Vt level corresponding to a programmed state;

initiating a transfer of the an other stored data value from the memory cell of the at least the third fuse circuit having the memory cell adjusted to the third Vt level to a latch of the at least the third fuse circuit; and

reading an output of the latch of the at least the third fuse circuit having the memory cell adjusted to the third Vt level after detecting the output change of the latch of the fuse circuit having the memory cell adjusted to the first Vt level.

16. The method of claim 15, wherein initiating the transfer of the an other stored data value to the latch of the at least the third fuse circuit includes:

applying the ramping voltage to an input node of the at least the third fuse circuit; and

applying the read voltage to a control gate of the memory cell of the at least the third fuse circuit having the memory cell adjusted to the third Vt level, the read voltage insufficient to place the memory cell adjusted to the third Vt level in a conducting state.

17. A memory device, comprising:

an array of memory cells;

a number of fuse circuits programmed to store data associated with operating the array; and

control circuitry coupled to the array and configured to;

initialize an output of at least one fuse circuit of the number of fuse circuits to a reset data value at least partially in response to detecting that a supply voltage has reached a threshold level;

detect when the output of the at least one initialized fuse circuit changes from the reset data value to a data value stored by a memory cell of the at least one initialized fuse circuit; and

retrieve data from an output of at least an other one of the number of fuse circuits at least partially in response to the detected output change.

18. The memory device of claim 17, wherein the memory cell of the at least one initialized fuse circuit has a first threshold voltage (Vt) level corresponding to the stored data value, the first Vt level is such that the memory cell of the at least one initialized fuse circuit is in a conductive state when a particular read voltage is applied to its control gate.

19. The memory device of claim 18, wherein the at least the other one of the number of fuse circuits includes a memory cell having a second Vt level greater in magnitude than the first Vt level of the memory cell of the at least one initialized fuse circuit such that the memory cell having the second Vt level is in a conductive state when the particular read voltage is applied to its control gate.

20. The memory device of claim 19, wherein:

the at least one initialized fuse circuit includes a latch to which the stored data value is transferred when the particular read voltage is applied to the memory cell having the first Vt level; and

the at least the other one of the number of fuse circuits includes a latch to which data stored by the memory cell having the second Vt level is transferred when the particular read voltage is applied to the memory cell having the second Vt level.

21. The memory device of claim 17, wherein the control circuitry is configured to provide a ready-busy signal in response to the detected output change of the at least one initialized fuse circuit.

22. The memory device of claim 17, wherein the memory cell of the at least one initialized fuse circuit and the memory cell of the at least the other one of the number of fuse circuits are floating gate memory cells.

23. The memory device of claim 17, wherein the array is a NAND array of floating gate memory cells.

24. The memory device of claim 17, wherein the device includes a threshold detector from which a signal is received while the supply voltage is ramping during power up of the device, the signal indicating that the supply voltage has reached the threshold level.

25. The memory device of claim 17, wherein the data retrieved from the output of the at least the other one of the number of fuse circuits includes address redundancy data associated with the array of memory cells.

26. The memory device of claim 17, wherein the data retrieved from the output of the at least the other one of the number of fuse circuits includes trim value data associated with operating the array of memory cells.

27. The memory device of claim 17, wherein each of the number of fuse circuits include at least two floating gate memory cells having their control gates coupled to a common select line and which are programmed to store complementary data values.

28. A fuse circuit of a memory device, the fuse circuit comprising:

a memory cell having a first threshold voltage (Vt) level corresponding to a stored data value;

a latch to which the stored data value is transferred when a read voltage sufficient to place the memory cell in a conductive state is applied to a control gate of the memory cell; and

wherein the first Vt level is lesser in magnitude than a second Vt level to which a memory cell of a number of other fuse circuits of the device are adjusted, and wherein data values stored by the number of other fuse circuits are retrieved during power up of the device after control circuitry of the device;

resets an output of the latch to a reset value different than the stored data value in response to a voltage used during operation of at least one the fuse circuits reaching a threshold value; and

detects a change of the output of the latch from the reset value to the stored data value.