Ramp rate control for peak and average current reduction of open blocks
Aspects of a storage device including a memory and a controller are provided which allow for reduction of current in open blocks during read operations using read voltage ramp rate control. The controller determines whether a block is open or closed. If the block is closed, the controller causes a read voltage to be applied to one of the block's word lines at a first ramp rate. If the block is open, the controller causes a read voltage to be applied to another of the block's word lines at a slower, second ramp rate. The controller further causes a read voltage to be applied to another word line of the open block at a different, third ramp rate. Thus, read voltages for open blocks may ramp slower than read voltages for closed blocks, as well as ramp at different rates for different word lines in open blocks.
1. A storage device, comprising:
a memory comprising a block including a plurality of word lines; and
a controller configured to determine whether the block is open or closed, to cause a first read voltage to be applied to a first one of the word lines of the block at a first ramp rate in response to determining the block is closed, and to cause a second read voltage to be applied to a second one of the word lines of the block at a second ramp rate slower than the first ramp rate in response to determining the block is open.
2. The storage device of claim 1 , wherein the block includes a string of cells coupled to the plurality of word lines.
3. The storage device of claim 2 , wherein a third one of the word lines coupled to the string is associated with a larger address than the second one of the word lines coupled to the string.
4. The storage device of claim 2 , wherein a third one of the word lines coupled to the string is associated with a smaller address than the second one of the word lines coupled to the string.
5. The storage device of claim 1 , wherein the block includes cells coupled to the plurality of word lines, and wherein the controller is further configured to cause a third read voltage to be applied to a third one of the word lines at a third ramp rate faster than the second ramp rate when one of the cells coupled to the third one of the word lines is in a programmed state.
6. The storage device of claim 1 , wherein the block includes cells coupled to the plurality of word lines, and wherein the controller is further configured to cause a third read voltage to be applied to a third one of the word lines at a third ramp rate slower than the second ramp rate when one of the cells coupled to the third one of the word lines is not in a programmed state.
7. The storage device of claim 1 , wherein the block includes cells coupled to the plurality of word lines, and wherein, in response to determining the block is open, the controller is further configured to cause the second read voltage applied to the second one of the word lines to charge to a first target voltage, and to cause a third read voltage applied to a third one of the word lines to charge to a second target voltage less than the first target voltage when one of the cells coupled to the third one of the word lines is not in a programmed state.
8. The storage device of claim 1 , wherein the controller is further configured to cause the second read voltage applied to the second one of the word lines to charge in a number of stages in response to determining the block is open.
9. The storage device of claim 1 , wherein the block includes cells coupled to the plurality of word lines, and wherein, in response to determining the block is open, the controller is further configured to cause the second read voltage to be applied to the second one of the word lines and to cause a third read voltage to be applied to a third one of the word lines based on a total number of word lines in the block or a current tolerance of the cells in the block.
10. A storage device, comprising:
a memory comprising a block including a plurality of word lines; and
a controller configured to determine whether the block is open, to cause a first read voltage to be applied to a first one of the word lines of the block at a first ramp rate in response to determining the block is open, and to cause a second read voltage to be applied to a second one of the word lines of the block at a second ramp rate different than the first ramp rate.
11. The storage device of claim 10 , wherein the block includes cells coupled to the plurality of word lines, and wherein the second ramp rate is faster than the first ramp rate when one of the cells coupled to the second one of the word lines is in a programmed state.
12. The storage device of claim 10 , wherein the block includes cells coupled to the plurality of word lines, and wherein the second ramp rate is slower than the first ramp rate when one of the cells coupled to the second one of the word lines is not in a programmed state.
13. The storage device of claim 10 , wherein the block includes cells coupled to the plurality of word lines, and wherein, in response to determining the block is open, the controller is further configured to cause the first read voltage applied to the first one of the word lines to charge to a first target voltage, and to cause the second read voltage applied to the second one of the word lines to charge to a second target voltage less than the first target voltage when one of the cells coupled to the second one of the word lines is not in a programmed state.
14. The storage device of claim 10 , wherein the controller is further configured to cause the first read voltage applied to the first one of the word lines to charge in a number of stages in response to determining the block is open.
15. The storage device of claim 10 , wherein the block includes cells coupled to the plurality of word lines, and wherein, in response to determining the block is open, the controller is further configured to cause the first read voltage to be applied to the first one of the word lines and to cause the second read voltage to be applied to the second one of the word lines based on a total number of word lines in the block or a current tolerance of the cells in the block.
16. A storage device, comprising:
a memory comprising a first block and a second block each including a plurality of word lines; and
a controller configured to determine whether the first block is open or closed, and to cause a first read voltage to be applied to a first one of the word lines of the first block at a first ramp rate in response to determining the first block is closed;
wherein the controller is further configured to determine whether the second block is open or closed, to cause a second read voltage to be applied to a second one of the word lines of the second block at a second ramp rate slower than the first ramp rate in response to determining the second block is open, and to cause a third read voltage to be applied to a third one of the word lines of the second block at a third ramp rate different than the second ramp rate.
17. The storage device of claim 16 , wherein the second block includes cells coupled to the plurality of word lines, and wherein the third ramp rate is faster than the second ramp rate when one of the cells coupled to the third one of the word lines is in a programmed state.
18. The storage device of claim 16 , wherein the second block includes cells coupled to the plurality of word lines, and wherein the third ramp rate is slower than the second ramp rate when one of the cells coupled to the third one of the word lines is not in a programmed state.
19. The storage device of claim 16 , wherein the controller is further configured to cause the second read voltage applied to the second one of the word lines to charge in a number of stages in response to determining the second block is open.
20. The storage device of claim 16 , wherein the second block includes cells coupled to the plurality of word lines, and wherein, in response to determining the second block is open, the controller is further configured to cause the second read voltage applied to the second one of the word lines to charge to a first target voltage, and to cause the third read voltage applied to the third one of the word lines to charge to a second target voltage less than the first target voltage when one of the cells coupled to the third one of the word lines is not in a programmed state.