Sense amplifier design for ramp sensing
AssigneeSanDisk Technologies LLC
InventorsAnirudh Amarnath, Tai-Yuan Tseng
Life of this patent
Estimating the term…
Abstract
Methods and systems for sensing memory cells using a sense amplifier that can support both ramp sensing and conventional sensing are described. With ramp sensing, a word line of a memory array may be ramped up linearly and a sensing operation may be performed by the sense amplifier while the word line is continuously being ramped up. In this case, during the sensing operation, the sense amplifier may sense a bit line of the memory array connected to a memory cell while the word line is ramping up and then transfer the result into a data latch. In contrast, with conventional sensing, a bit line of the memory array may be first precharged to a particular voltage level (e.g., a read voltage level) and then sensed while the word line is held at the particular voltage level.
Claims20
An apparatus, comprising:
- a sensing circuit configured to precharge a sensing node of the sensing circuit to a second voltage if a voltage of a feedback node of the sensing circuit is less than a second transistor threshold voltage below the second voltage, the sensing circuit configured to charge up the feedback node in response to a voltage of the sensing node dropping at least a first transistor threshold voltage below the second voltage during a sensing operation;
- and
- a feedback circuit configured to set the feedback node to the second voltage if the voltage of the feedback node rises to more than a third transistor threshold voltage above a reference voltage during the sensing operation.
A method, comprising:
- precharging a sensing node of a sense amplifier to a second voltage;
- detecting that the sensing node has dropped at least a transistor threshold voltage below the second voltage during a sensing operation;
- and
- disabling the sensing node from precharging during one or more other sensing operations subsequent to the sensing operation in response to detecting that the sensing node has dropped at least the first transistor threshold voltage below the second voltage, the disabling the sensing node includes setting a feedback node of the sense amplifier to the second voltage using a feedback circuit that pulls up the feedback node to the second voltage if the feedback circuit detects that the feedback node has risen more than a second transistor threshold voltage above a reference voltage.
A system, comprising:
- a sense amplifier including a precharge path and a sensing path, the sense amplifier configured to precharge a sensing node of the sense amplifier to a second voltage using the precharge path and detect that a voltage of the sensing node has dropped at least a PMOS transistor threshold voltage below the second voltage using the sensing path during a sensing operation, the sense amplifier configured to charge up a feedback node of the sense amplifier in response to the voltage of the sensing node dropping at least the PMOS transistor threshold voltage below the second voltage during the sensing operation;
- and
- a feedback circuit configured to disable the sensing node from precharging during one or more other sensing operations subsequent to the sensing operation in response to the feedback node rising to more than an NMOS transistor threshold voltage above a reference voltage during the sensing operation.
Dependencies are inferred from the claim text.