Sandisk Technologies Inc.

Western Digital Technologies, Inc.

Juan Lee

Man Lung Mui

Hao Nguyen

Seungpil Lee

Jongmin Park

Huai-Yuan Tseng

Yu-Chung Lien

Tien-Chien Kuo

Yuki Mizutani

Sung-En Wang

Masahide Matsumoto

Yee Lih Koh

Alexander Tsang-Nam Chu

Aspects of a storage device including a memory and a controller are provided which allow for reduction of current during program operations using pre-charge timing control based on an inhibit bit line count acquired from data latches. When the inhibit bit line count is within a bit line count range, the controller pre-charges bit lines in memory during a first time period to a first target voltage, and when the inhibit bit line count is outside the bit line count range, the controller pre-charges the bit lines during a second, earlier time period to a second, smaller target voltage. The controller is thus configured to reduce current and minimize operation overlaps in the earlier time period during the middle of the program operation where current is highest. Thus, a balance in power consumption and performance may be achieved during program operations using timing control.

Pre-charge timing control for peak current based on data latch count

Aspects of a storage device including a memory and a controller are provided which allow for reduction of current during program operations using pre-charge ramp rate control based on an inhibit bit line count acquired from data latches. When the inhibit bit line count is within a bit line count range, the controller pre-charges bit lines in memory at a first ramp rate to a first target voltage, and when the inhibit bit line count is outside the bit line count range, the controller pre-charges the bit lines at a second, faster ramp rate to a second, smaller target voltage. The inhibit bit line count may increase throughout a program operation, and the bit line count range may be configured for the middle of the program operation where current is typically high. Thus, a balance in power consumption and performance may be achieved during program operations using ramp rate control.

Pre-charge ramp rate control for peak current based on data latch count

In NAND Flash memory, bit line precharge/discharge times can be a main component in determining program, erase and read performance. In a conventional arrangement bit line levels are set by the sense amps and bit lines are discharged to a source line level is through the sense amplifier path. Under this arrangement, precharge/discharge times are dominated by the far-side (relative to the sense amps) based on the bit lines' RC constant. Reduction of bit line precharge/discharge times, therefore, improves NAND Flash performance and subsequently the overall system performance. To addresses this, an additional path is introduced between bit lines to the common source level through the use of dummy NAND strings. In an exemplary 3D-NAND (BiCS) based embodiment, the dummy NAND strings are taken from dummy blocks, where the dummy blocks can be placed throughout the array to evenly distribute the discharging current.

Utilizing NAND strings in dummy blocks for faster bit line precharge

A compact and versatile high speed sense amplifier suitable for use in non-volatile memory circuits is presented. The sense amp includes a latch, which is connected to a data bus, and bit line selection circuitry by which it can selectively be connected to one or more bit lines. The sense amp also includes some intermediate circuitry having a first node connectable to a selected bit line through the bit line selection circuitry and a second node that is connectable to the latch circuit. The sense amp can include switches where the second node can be connected to either the value held in the latch or the inverse of the value held in the latch. The sense amp can also include a switch where an internal node of the sense amp can be connected directly to a voltage supply level.

Compact high speed sense amplifier for non-volatile memory

When writing a multi-state non-volatile memory, a de-trapping operation is included in the programming cycle. To reduce the performance penalty of including a de-trapping operation, the programming cycle of a single series of increasing pulses alternating with verify operations is replaced with a cycle including a pulse from each of two or more staircases, where each staircase is for a corresponding subset of the data states. After the multiple pulses, but before the following verify, a de-trapping operation is inserted in the programming cycle.

Multi-pulse programming cycle of non-volatile memory for enhanced de-trapping

In non-volatile memory devices, a write typically consists of an alternating set of pulse and verify operations. At the end of a pulse, the device must be biased properly for an accurate verify, after which the device is re-biased for the next pulse. The intervals between the pulse and verify phases are considered. For the interval after a pulse, but before establishing the verify conditions, the source, bit line, and, optionally, the well levels can be equalized and then regulated at a desired DC level. After a verify phase, but before applying the biasing the memory for the next pulse, the source and bit line levels can be equalized to a DC level.

Charge cycling by equalizing and regulating the source, well, and bit line levels during write operations for NAND flash memory: program to verify transition

Charge cycling by equalizing and regulating the source, well, and bit line levels during write operations for NAND flash memory: verify to program transition

In non-volatile memory devices, a write typically consists of an alternating set of pulse and verify operations. At the end of a pulse, the device must be biased properly for an accurate verify, after which the device is re-biased for the next pulse. In some cases a non-volatile memory is programmed by an alternating set of pulses, but, for at least some pulses without any intervening verify operations. After a one pulse, but before biasing the memory for the next pulse without an intervening very, the source and bit line levels can be left to float.

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Sunnyvale, CA, United States of America

Juan Lee