Suppression of peak ICC during block selection in non-volatile memories
To reduce Icc spikes during the operation of a non-volatile memory device, different block decoding parameters can be used based on whether a block is open or closed. For blocks that are open or in other high Icc conditions, such as first read, the timing for the block decode control signals, the block decode voltage levels, or a combination of these can be used to lower Icc spikes.
1 . A non-volatile memory system, comprising:
a control circuit configured to connect to one or more memory arrays each comprising a plurality of blocks of non-volatile memory cells connected along word lines and having a NAND architecture, the control circuit comprising:
bias circuitry configured to generate one or more word line voltage levels, including a bypass voltage for non-selected word lines; and
block select circuitry configured to transmit the one or more word line voltage levels to word lines of a selected block, including one or more transfer gates connected between the bias circuitry and word lines of the selected blocks and level shifter circuitry connected to control the one or more transfer gates,
the control circuit configured to:
select a first block on which to perform a first sensing operation;
determine whether the first block is in a high peak current condition;
based on whether or not the first block is the high peak current condition, select either a first set of block select parameters, when the block is not in the high peak current condition, or a second set of block select parameters, when the block is in the high peak current condition; and
use the selected set of block select parameters to operate the level shifter circuitry, where:
in response to the second set of block select parameters, the level shifter circuitry is configured to turn on the transfer gates at a first time to bias word lines of the selected block to a voltage level intermediate to ground and the bypass voltage, and to bias the word lines of the selected block at the bypass voltage at a second time subsequent to the first time, and
in response to the first set of block select parameters, the level shifter circuitry is configured to turn on the transfer gates to bias the word lines of the selected block to the bypass voltage at a time intermediate to the first time and the second time.
2 . The non-volatile memory system of claim 1 , further comprising:
a memory die comprising the memory arrays, wherein the control circuit is on a control die, separate from and bonded to the first die.
3 . The non-volatile memory system of claim 1 , wherein the first set of block select parameters differ from the second set of block select parameters in a timing value.
4 . The non-volatile memory system of claim 1 , wherein the first set of block select parameters differ from the second set of block select parameters in a voltage value.
5 . The non-volatile memory system of claim 1 , wherein to determine whether the first block is in the high peak current condition the control circuit is further configured to determine an extent to which the word lines of the block have been previously written.
6 . The non-volatile memory system of claim 1 , wherein to determine whether the first block is in the high peak current condition the control circuit is further configured to determine a time since the block was previously accessed.
7 . The non-volatile memory system of claim 1 , wherein the first set of block select parameters differ from the second set of block select parameters in a voltage level of the second input voltage, the second input voltage being higher for the second set of block select parameters.
8 . The non-volatile memory system of claim 1 , wherein the first set of block select parameters differ from the second set of block select parameters in a duration of the enable signal, the enable signal being longer for the second set of block select parameters.
9 . The non-volatile memory system of claim 1 , wherein the first set of block select parameters differ from the second set of block select parameters in a time at which the bias circuitry begins to ramp up the first word line voltage, the ramp up beginning later for the second set of block select parameters than for the first set of block select parameters.
10 . The non-volatile memory system of claim 1 , bypass voltage is a read bypass voltage for non-selected word lines.
11 . The non-volatile memory system of claim 1 , wherein the first sensing operation is in response to a host request.
12 . The non-volatile memory system of claim 1 , wherein the first sensing operation is generated by the control circuit.
13 . The non-volatile memory system of claim 1 , wherein the first sensing operation is data read operation.
14 . The non-volatile memory system of claim 1 , wherein the first sensing operation is program verify operation.
15 . A method, comprising:
maintaining, for each of a plurality of blocks of non-volatile memory cells having a NAND architecture an indication of whether the block is open or closed;
selecting a block for a sensing operation;
selecting either a first set of select parameters or a second set of select parameters to decode the selected block in response to the selected block being open or closed, respectively; and
decoding the selected block using the selected set of select parameters, including:
in response to the second set of block select parameters, turning on one or more transfer gates by level shifter circuitry, the one or more transfer gates connected between bias circuitry and word lines of the selected block and the level shifter circuitry connected to control the one or more transfer gates, at a first time to bias the word lines of the selected block to a voltage level intermediate to ground and a bypass voltage for non-selected word lines, and to bias the word lines of the selected block at the bypass voltage at a second time subsequent to the first time, and
in response to the first set of block select parameters, turning on the transfer gates to bias the word lines of the selected block by the level shifter circuitry to the bypass voltage at a time intermediate to the first time and the second time.
16 . The method of claim 15 , where the first set of select parameters differ from the second set of select parameters in a timing value.
17 . The method of claim 15 , where the first set of select parameters differ from the second set of select parameters in a voltage value.
18 . A non-volatile memory system, comprising:
one or more memory arrays each comprising a plurality of blocks of non-volatile memory cells connected along word lines and having a NAND architecture;
bias circuitry configured to generate one or more word line voltage levels, including a bypass voltage for non-selected word lines;
decoding circuitry connected to the one or more arrays and configured to select a specified block for a memory operation, including:
one or more transfer gates connected between the bias circuitry and the word lines of the specified block; and
level shifter circuitry connected to control the one or more transfer gates; and
one or more control circuits connected to the one or more of memory array, to the bias circuitry, and to the decoding circuitry, the one or more control circuits configured to:
maintain, for each of the blocks, an indication of whether the block is open or closed;
selecting a block for a sensing operation;
select either a first set of select parameters or a second set of select parameters to decode the selected block in response to the selected block being open or closed, respectively; and
decode the selected block using the selected set of select parameters, including:
in response to the second set of block select parameters, turning on one or more transfer gates by level shifter circuitry, the one or more transfer gates connected between bias circuitry and word lines of the selected block and the level shifter circuitry connected to control the one or more transfer gates, at a first time to bias the word lines of the selected block to a voltage level intermediate to ground and a bypass voltage for non-selected word lines, and to bias the word lines of the selected block at the bypass voltage at a second time subsequent to the first time, and
in response to the first set of block select parameters, turning on the transfer gates to bias the word lines of the selected block by the level shifter circuitry to the bypass voltage at a time intermediate to the first time and the second time.
19 . The non-volatile memory system of claim 18 , where the first set of parameters differ from the second set of select parameters in a timing value.