Current-Mode Sense Amplifier With Switched Equalization for Fast Latching
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Solution Overview
Problem
Existing sense amplifiers face challenges in achieving high-speed sensing with low power consumption and reduced silicon area requirements, particularly in efficiently transforming current differences into binary information for memory cell state reading.
Innovation Solution
A current-mode sense amplifier circuit with a differential input stage, cross-coupled NMOS and PMOS transistors, and a transistor switch that disconnects the current mirror structure after the equalization phase to enhance sensing speed and reduce power consumption, allowing the output voltages to reach rail-to-rail values quickly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the current mirror structure remains connected during the sensing phase, then the sensing accuracy is maintained, but the sensing time increases and power consumption increases
Solution Approach 1:
The sensing operation is divided into two distinct phases: equalization phase where the current mirror is connected to establish initial conditions, and sensing phase where the current mirror is disconnected to enable rapid latching. This temporal segmentation allows the system to achieve both accurate sensing and fast response by optimizing the circuit configuration for each specific phase requirement.
Solution Approach 2:
The circuit transitions dynamically between different operational states by controlling the transistor switch. During the equalization phase, the switch connects the current mirror structure. During the sensing phase, the switch disconnects the current mirror structure, enabling the cross-coupled transistors to latch rapidly. This dynamic reconfiguration optimizes performance for each phase while reducing overall sensing time and power consumption.
2Stability of the object's composition
If the transistor switch keeps the drain nodes shorted throughout the sensing phase, then the circuit stability is maintained, but the sensing speed decreases and power consumption increases
Solution Approach 1:
The transistor switch operates periodically, being closed during the equalization phase to maintain circuit stability and open during the sensing phase to enable fast latching. This periodic switching action allows the circuit to achieve both stability during initialization and high speed during the actual sensing operation, resolving the contradiction between stability and speed.
3Device complexity
If the sense amplifier uses traditional voltage-mode operation, then the circuit design is simpler, but the power consumption increases and sensing speed decreases
Solution Approach 1:
The patent replaces traditional voltage-mode operation with current-mode operation. This substitution fundamentally changes the operating principle of the sense amplifier, enabling faster sensing speeds and lower power consumption while maintaining relatively simple circuit design through the use of cross-coupled transistors and a transistor switch for phase control.
Data Source
AI summary
A sense amplifier circuit according to some implementations includes a differential input stage to receive mirrored input currents and a transistor switch whose state is controlled by a signal applied to its gate. The sense amplifier circuit includes a pair of cross-coupled NMOS transistors and a pair of cross-coupled PMOS transistors to which the mirrored input currents are coupled and whose drain nodes are shorted when the transistor switch is in a conductive state. The sense amplifier is arranged to generate a digital output signal indicative of which of the input currents is larger.