Data retention-specific refresh read
A storage device is provided that conditionally performs read refresh in blocks having higher P/E cycles or older programming times, while refraining from performing read refreshes in blocks having lower P/E cycles or recent programming times. The storage device includes a memory and a controller. The memory includes a block having cells. The controller performs a read refresh on the cells when a number of P/E cycles of the block exceeds an age threshold or after a threshold amount time has elapsed since data was programmed in the block. The controller may also refrain from performing read refreshes on the cells until the number of P/E cycles exceeds the age threshold or until a threshold amount of time has elapsed since the data is programmed. As a result, lower BER may occur due to wider Vt margins, while power and system overhead may be saved.
1. A storage device, comprising:
a memory including a block, the block including a plurality of cells; and
a controller coupled to the memory and configured to selectively perform a read refresh on the plurality of cells by applying periodic voltage read pulses to the plurality of cells without incurring a program/erase (P/E) cycle and without reading data in response to the periodic voltage read pulses in response to a number of P/E cycles of the block exceeding an age threshold,
wherein the periodic voltage read pulses are only performed on the plurality of cells based on the block exceeding the age threshold.
2. The storage device of claim 1 , further comprising:
a die comprising a plurality of blocks including the block, wherein the controller is configured to perform the read refresh on the plurality of cells in response to an average number of P/E cycles of each of the plurality of blocks in the die exceeding the age threshold.
3. The storage device of claim 2 , wherein the controller is configured to refrain from performing read refreshes on the plurality of cells until the average number of P/E cycles of each of the plurality of blocks in the die exceeds the age threshold.
4. The storage device of claim 1 , wherein the controller is configured to program the block, and to perform the read refresh on the plurality of cells a threshold amount of time after the block is programmed.
5. The storage device of claim 4 , wherein the controller is configured to refrain from performing read refreshes on the plurality of cells until the threshold amount of time has elapsed.
6. The storage device of claim 4 , wherein the controller is configured to store a time tag associated with the block indicating when data is programmed in the block, and to determine whether the threshold amount of time has elapsed based on the time tag.
7. The storage device of claim 6 , wherein the memory further includes a control block, and wherein the controller is configured to store the time tag associated with the block in the control block.
8. The storage device of claim 1 , wherein the controller is configured to program a plurality of blocks including the block, and to perform the read refresh on the plurality of cells in each of the plurality of blocks after a threshold amount of time after the plurality of blocks are programmed.
9. The storage device of claim 8 , wherein the controller is configured to refrain from performing read refreshes on the plurality of cells in each of the plurality of blocks until the threshold amount of time has elapsed.
10. The storage device of claim 8 , wherein the controller is configured to store a time tag associated with the plurality of blocks indicating when data is programmed in the plurality of blocks, and to determine whether the threshold amount of time has elapsed based on the time tag.
11. The storage device of claim 1 , wherein the controller is configured to refrain from performing read refreshes on the plurality of cells until the number of P/E cycles of the block exceeds the age threshold.
12. A storage device, comprising:
a memory including a block, the block including a plurality of cells; and
a controller coupled to the memory and configured to program the block, and to selectively apply dummy read pulses to the plurality of cells by applying periodic voltage read pulses to the plurality of cells without incurring a program/erase (P/E) cycle and without reading data in response to the periodic voltage read pulses after a threshold amount of time has elapsed since the block is programmed,
wherein the periodic voltage read pulses are only performed on the plurality of cells based on the block exceeding an age threshold.
13. The storage device of claim 12 , wherein the controller is configured to refrain from applying the dummy read pulses to the plurality of cells until the threshold amount of time has elapsed.
14. The storage device of claim 12 , wherein the controller is configured to store an indicator of a time when data is programmed in the block, and to determine whether the threshold amount of time has elapsed since the time when the data is programmed in the block.
15. The storage device of claim 14 , wherein the memory further includes a control block, and wherein the controller is configured to store the indicator in the control block.
16. The storage device of claim 12 , wherein the controller is configured to apply the dummy read pulses to the plurality of cells in response to a number of P/E cycles of the block exceeding the age threshold.
17. The storage device of claim 16 , wherein the controller is configured to refrain from applying the dummy read pulses to the plurality of cells until the number of P/E cycles of the block exceeds the age threshold.
18. A storage device, comprising:
a memory including a block, the block including a plurality of cells; and
a controller coupled to the memory and configured to program data in the block, and to refrain from performing a read refresh procedure on the plurality of cells that includes selectively applying periodic voltage read pulses to the plurality of cells without incurring a program/erase (P/E) cycle and without reading data in response to the periodic voltage read pulses until a number of P/E cycles of the block exceeds an age threshold and until a threshold amount of time has elapsed since the data is programmed in the block,
wherein the periodic voltage read pulses are only performed on the plurality of cells based on the block exceeding the age threshold.
19. The storage device of claim 18 , further comprising:
a die comprising a plurality of blocks including the block, wherein the controller is configured to refrain from performing read refreshes until an average number of P/E cycles of each of the plurality of blocks in the die exceeds the age threshold.
20. The storage device of claim 18 , wherein the controller is configured to store a time tag associated with the block indicating when data is programmed in the block, to determine whether the threshold amount of time has elapsed based on the time tag, and to perform read refreshes in response to the determination that the threshold amount of time has elapsed based on the time tag.