Self-Timed Sense Amplifier Using P-Channel Control Transistors
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Solution Overview
Problem
Conventional sense amplifiers for non-volatile memory cells consume significant power, especially in low voltage integrated circuits, and may output corrupted data due to metastable states, particularly in circuits with voltages less than 1.8 V, such as those manufactured using the 180 nanometer CMOS process.
Innovation Solution
A low power sense amplifier design that includes a latch with cross-coupled inverting gates, p-channel control transistors, and a clamp circuit activated by an OR gate when data signals reach a threshold voltage, eliminating the need for large n-channel isolation transistors and enabling self-timed operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If conventional sense amplifiers use n-channel isolation transistors in the precharge path, then the sense amplifier can operate, but power consumption increases significantly due to charge pump efficiency problems
Solution Approach 1:
The patent inverts the transistor type used for isolation from n-channel to p-channel. P-channel isolation transistors are used instead of n-channel transistors, which eliminates the need for charge pumps and significantly reduces power consumption while maintaining the same functional capability of isolating the sense input during precharge and read phases.
Solution Approach 2:
The patent changes the threshold voltage parameter by using p-channel transistors with different threshold characteristics compared to n-channel transistors. This parameter change allows the isolation transistors to operate effectively without requiring boosted voltages, thereby reducing power consumption and simplifying the device structure.
2Reliability
If conventional sense amplifiers operate at low voltages (less than 1.8 V), then the circuit can function, but metastable states occur causing corrupted data output
Solution Approach 1:
The patent uses p-channel transistors instead of n-channel transistors for isolation, which changes the voltage threshold characteristics. This inversion helps the sense amplifier maintain stable operation at low voltages by preventing metastable states, thereby improving data accuracy without requiring higher power consumption.
Solution Approach 2:
The patent employs a simplified transistor structure that is more suitable for low-voltage operation. The p-channel transistors provide a more reliable switching characteristic at low voltages, eliminating the need for complex charge pump circuits and reducing power consumption while ensuring accurate data output.
3Use of energy by moving object
If p-channel control transistors are used to power latch sections, then power consumption is reduced, but the transistors must be brought to conducting state carefully to avoid metastability
Solution Approach 1:
The patent implements self-timed operation where the latch automatically transitions to the conducting state when the sense input voltage drops below a threshold. The p-channel control transistors are automatically activated by the voltage change during the read phase, eliminating the need for external timing control signals and simplifying operation while maintaining low power consumption.
Solution Approach 2:
The patent uses voltage feedback to control the p-channel transistors. When the sense input voltage drops below a threshold during the read phase, the transistor automatically turns on. This feedback mechanism ensures the transistor is activated at the correct moment without requiring complex control logic, thereby reducing control complexity while maintaining low power consumption.
Data Source
AI summary
A sense amplifier is disclosed comprising a first sense input, a second sense input, a latch, a first p-channel control transistor arranged to electrically power a first section of the latch and having a gate terminal linked to the first sense input, and a second p-channel control transistor arranged to electrically power a second section of the latch and having a gate terminal linked to the second sense input. Application may be in particular to low power embedded memories.