DRAM Sense Amplifier Offset Compensation for Low-Voltage Sensing
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Solution Overview
Problem
The decreasing supply voltage and device size in DRAMs, coupled with threshold voltage mismatches due to process and temperature changes, lead to insufficient sensing margins and offset noise, impairing the sense amplifier's ability to effectively amplify signals.
Innovation Solution
A sense amplifier design incorporating specific switch transistors and a control method with sequential stages (pre-charge, offset compensation, charge sharing, equalization, pre-sensing, and restoring) to manage voltage equalization and eliminate threshold voltage mismatches, enhancing sensing margin and signal amplification.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the supply voltage and device size of the DRAM are reduced, then the integration density is improved, but the sensing margin of the sense amplifier decreases
Solution Approach 1:
The patent applies preliminary action by performing offset compensation before the sensing operation. The control circuit pre-adjusts the sensing bitlines to equalize threshold voltage differences between transistors before data is read, thereby eliminating offset noise in advance and ensuring sufficient sensing margin even with reduced supply voltage and device size.
Solution Approach 2:
The patent introduces a control circuit as an intermediary component that actively manages the sensing bitlines. This control circuit includes switching transistors and capacitors that mediate between the memory cells and the sense amplifier, providing voltage adjustment and offset compensation to maintain reliable sensing despite scaling effects.
2Device complexity
If traditional sense amplifier design is used, then the device complexity is low, but offset noise occurs due to threshold voltage mismatch
Solution Approach 1:
The patent implements feedback by using the control circuit to continuously monitor and adjust the voltages on the sensing bitlines. The control circuit detects threshold voltage mismatches and applies compensating voltages through switching transistors, creating a feedback mechanism that eliminates offset noise while maintaining relatively simple circuit structure.
3Speed
If offset compensation is not performed, then the operation speed is fast, but the sensing accuracy is insufficient
Solution Approach 1:
The patent performs offset compensation as a preliminary action before the actual sensing operation. The control circuit quickly equalizes the sensing bitlines to compensate for threshold voltage mismatches in advance, then immediately proceeds to the sensing operation. This preliminary compensation ensures both high sensing accuracy and fast operation speed by eliminating the need for slow iterative correction during sensing.
Data Source
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AI summary
The present disclosure relates to a sense amplifier, a control method of the sense amplifier, and a memory. The sense amplifier includes: a first power input terminal, a second power input terminal, a first switch transistor, a second switch transistor, a third switch transistor, a fourth switch transistor, a fifth switch transistor, a first negative-channel metal-oxide semiconductor (NMOS) transistor, a second NMOS transistor, a first positive-channel metal-oxide semiconductor (PMOS) transistor and a second PMOS transistor. When the sense amplifier operates, appropriate sequential logic signals are output to the five switch transistors respectively to control the on and off of the five switch transistors, thereby eliminating offset noise caused by a threshold voltage mismatch between the first NMOS transistor and the second NMOS transistor.